Research activity information

• Dec. 2006 海洋調査技術学会, 海洋調査技術学会技術賞, 論文「瀬戸内海播磨灘での海底重力測定」

  上嶋 正人, 石原 丈実, 小泉 金一郎, SEAMA N, 押田 淳, 藤本 博巳, 金澤 敏彦

• Development of three-dimensional forward modeling method for the magnetometric resistivity (MMR) method

  Noriko Tada, Motoyuki Kido, Nobukazu Seama

  Abstract We have developed a 3-D forward modeling method for the magnetometric resistivity (MMR) technique, specially focusing on the marine MMR method, which utilizes a vertical bipole source and seafloor receivers to measure magnetic field variations. The bipole source generates an artificial electric current between two electrodes: one on the sea surface and another on the seafloor. When computing the electric potential using the relaxation method, while conserving electric current, singularities arise at the electrode locations. To address this issue, we introduce two electrical resistivity structures to mitigate the effects of these singularities and to obtain magnetic field anomalies caused by arbitrary 3-D electrical resistivity anomalies beneath the seafloor. By determining the sign of the magnetic field anomaly, we can infer whether the electrical resistivity of the anomalous body is more conductive or more resistive compared to the surrounding oceanic crust. Furthermore, we demonstrate that increasing the number of bipole sources is more effective in exploring anomalous bodies than increasing the number of receivers. Graphical abstract

  Springer Science and Business Media LLC, Oct. 2024, Earth, Planets and Space, 76(1) (1), 130

  [Refereed]

  Scientific journal


• Submarine cores record magma evolution toward a catastrophic eruption at Kikai Caldera

  Takeshi Hanyu, Nobukazu Seama, Katsuya Kaneko, Qing Chang, Reina Nakaoka, Koji Kiyosugi, Yuzuru Yamamoto, Tetsuo Matsuno, Keiko Suzuki-Kamata, Yoshiyuki Tatsumi

  Aug. 2024, Communications Earth & Environment, 5, 428

  [Refereed]

  Scientific journal


• Submarine pyroclastic deposits from 7.3 ka caldera-forming Kikai-Akahoya eruption

  Satoshi Shimizu, Reina Nakaoka, Nobukazu Seama, Keiko Suzuki-Kamata, Katsuya Kaneko, Koji Kiyosugi, Hikaru Iwamaru, Mamoru Sano, Tetsuo Matsuno, Hiroko Sugioka, Yoshiyuki Tatsumi

  Elsevier BV, Apr. 2024, Journal of Volcanology and Geothermal Research, 448, 108017 - 108017

  [Refereed]

  Scientific journal


• Shallow structure and late quaternary slip rate of the Osaka Bay fault, western Japan

  Mari Hamahashi, Hironori Otsuka, Yoshiaki Suzuki, Jun Arimoto, Tetsuo Matsuno, Nobukazu Seama, Yuzuru Yamamoto, Hiroko Sugioka, Stephen A. Bowden, Satoshi Shimizu, Hikaru Iwamaru, Mamoru Sano, Keita Suzuki, Katsuya Kaneko, Kazuo Nakahigashi, Yoshiyuki Tatsumi

  Abstract The Osaka Bay is situated at a seismically active region north of the Median Tectonic Line and east of Awaji Island in western Japan, known as part of the Kinki Triangle and the Niigata–Kobe Tectonic Zone. Dense distribution of active faults and high geodetic strain rates characterize the region, posing a major seismic hazard potential to the coastal and metropolitan areas of the Kansai region. To investigate the shallow structure and recent deformation history of active faults in the Osaka Bay, we acquired 15 high-resolution seismic profiles using a Mini-GI airgun and a Boomer as active sources, together with multi-beam bathymetry data across the Osaka Bay Fault. Our seismic sections image a ~ 0.1 to 3.7 km-wide asymmetric anticline forelimb above the Osaka Bay Fault at shallow depths, coupled with a ~ 2.6 km-wide syncline to the west, and a broad, ~ 11 km-wide syncline in the footwall to the east. The synclinal axial surface at shallow depths measured in this study ranges 75°–89°. We observe the vertical displacement of the Osaka Bay Fault increasing northwards along strike. The sediment thickness on the hanging wall, however, is variable, modified by non-tectonic processes such as by tidal currents, affecting the geometry of growth strata. The most recent deformation by the Osaka Bay Fault reaches to near the seafloor by active folding, with large vertical offsets of 8–14 m over the last ~ 11 ka, and 5–11 m over the last ~ 5 ka. By combining with previously reported borehole age data, the average uplift rate on the Osaka Bay Fault is estimated to be ~ 1.0 to 1.7 m/ka during the Latest Pleistocene to Holocene. The inferred slip of the Osaka Bay Fault during the Holocene is likely to account for > 5% of the regional geodetic strain accumulation within the Kinki Triangle. Further studies to evaluate the Holocene slip rates of regional faults are necessary to assess the seismic hazards and the internal strain budgets within the Kinki Triangle and the Niigata–Kobe Tectonic Zone. Graphical abstract

  Springer Science and Business Media LLC, Feb. 2024, Progress in Earth and Planetary Science, 11(1) (1)

  [Refereed]

  Scientific journal


• Undulations in Subducted Oceanic Crust Correlate With Shallow Tremor Distribution in the Kuril Trench Off Hokkaido

  Hiroto Yamaguchi, Shuichi Kodaira, Gou Fujie, Tetsuo No, Yasuyuki Nakamura, Kazuya Shiraishi, Nobukazu Seama

  Abstract Recent research has shown that shallow tremors tend to occur in spatial association with heterogeneous conditions, which are formed by seamounts or ridges on the subducted oceanic crust. In the southern Kuril Trench, shallow tremors have been observed on the western side, although no apparent heterogeneity in the subducted oceanic crust has been identified. To investigate structures spatially associated with these shallow tremors, we processed reflection seismic data acquired along seven profiles. We examined structures ranging from the seafloor to the top of the oceanic crust, within a depth of up to 20 km. Our results reveal that undulations observed at the top of the subducted oceanic crust are related to the distribution and number of shallow tremors. The undulations would play a crucial role in the distribution of shallow tremors.

  American Geophysical Union (AGU), Dec. 2023, Geophysical Research Letters, 51(1) (1)

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Evolution of magma supply system beneath a submarine lava dome after the 7.3-ka caldera-forming Kikai-Akahoya eruption

  Morihisa Hamada, Takeshi Hanyu, Iona M. McIntosh, Maria Luisa G. Tejada, Qing Chang, Katsuya Kaneko, Jun-Ichi Kimura, Koji Kiyosugi, Takashi Miyazaki, Reina Nakaoka, Kimihiro Nishimura, Tomoki Sato, Nobukazu Seama, Keiko Suzuki-Kamata, Satoru Tanaka, Yoshiyuki Tatsumi, Kenta Ueki, Bogdan S. Vaglarov, Kenta Yoshida

  Elsevier BV, Feb. 2023, Journal of Volcanology and Geothermal Research, 434, 107738 - 107738

  [Refereed]

  Scientific journal


• Enhanced and Asymmetric Melting Beneath the Southern Mariana Back‐Arc Spreading Center Under the Influence of Pacific Plate Subduction

  Tetsuo Matsuno, Nobukazu Seama, Haruka P. Shindo, Yoshifumi Nogi, Kyoko Okino

  The back-arc spreading at the southern Mariana is categorized as slow, but surface morphological and geophysical features of the spreading centers suggest that the spreading process is associated with enhanced melting in the upper mantle, due to water being derived from the subducted Pacific slab. A marine magnetotelluric experiment was performed along a transect across a segment at 13 degrees N to reveal the key processes of melting, dehydration, and dynamics in the upper mantle, and their relationships to the surface characteristics. Our inversion model of electrical resistivity shows (a) a conductive body at 10-20 km depth beneath the spreading axis, and (b) another conductive area expanding asymmetrically under and around the conductive body. Away from the spreading center, there is (c) a resistive area thickening up to similar to 40 km on the remnant arc side, and (d) another resistive area with a constant thickness of similar to 150 km on the trench side. Implications of these model features are (a) a melt body beneath the spreading axis; (b) a hydrous mantle above the subducted slab and asymmetric passive decompression melting in the mantle wedge; (c) a residual mantle off from the spreading axis; and (d) a cold mantle wedge tip and the subducted Pacific mantle. The structure markedly contrasts with that in the central Mariana Trough at 18 degrees N, suggesting that the horizontal distance between the location of the spreading center and the root of the buoyant upwelling above the subducted slab is a key parameter that controls the mantle dynamics beneath the back-arc spreading.

  American Geophysical Union (AGU), Mar. 2022, Journal of Geophysical Research: Solid Earth, 127(3) (3), English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Workshop report: Exploring deep oceanic crust off Hawai`i

  Susumu Umino, Gregory F. Moore, Brian Boston, Rosalind Coggon, Laura Crispini, Steven D'Hondt, Michael O. Garcia, Takeshi Hanyu, Frieder Klein, Nobukazu Seama, Damon A. H. Teagle, Masako Tominaga, Mikiya Yamashita, Michelle Harris, Benoit Ildefonse, Ikuo Katayama, Yuki Kusano, Yohey Suzuki, Elizabeth Trembath-Reichert, Yasuhiro Yamada, Natsue Abe, Nan Xiao, Fumio Inagaki

  Abstract. For more than half a century, exploring a complete sequence of the oceanic crust from the seafloor through the Mohorovičić discontinuity (Moho) and into the uppermost mantle has been one of the most challenging missions of scientific ocean drilling. Such a scientific and technological achievement would provide humankind with profound insights into the largest realm of our planet and expand our fundamental understanding of Earth's deep interior and its geodynamic behavior. The formation of new oceanic crust at mid-ocean ridges and its subsequent aging over millions of years, leading to subduction, arc volcanism, and recycling of some components into the mantle, comprise the dominant geological cycle of matter and energy on Earth. Although previous scientific ocean drilling has cored some drill holes into old (> 110 Ma) and young (< 20 Ma) ocean crust, our sampling remains relatively shallow (< 2 km into intact crust) and unrepresentative of average oceanic crust. To date, no hole penetrates more than 100 m into intact average-aged oceanic crust that records the long-term history of seawater–basalt exchange (60 to 90 Myr). In addition, the nature, extent, and evolution of the deep subseafloor biosphere within oceanic crust remains poorly unknown. To address these fundamentally significant scientific issues, an international workshop “Exploring Deep Oceanic Crust off Hawai`i” brought together 106 scientists and engineers from 16 countries that represented the entire spectrum of disciplines, including petrologists, geophysicists, geochemists, microbiologists, geodynamic modelers, and drilling/logging engineers. The aim of the workshop was to develop a full International Ocean Discovery Program (IODP) proposal to drill a 2.5 km deep hole into oceanic crust on the North Arch off Hawai`i with the drilling research vessel Chikyu. This drill hole would provide samples down to cumulate gabbros of mature (∼ 80 Ma) oceanic crust formed at a half spreading rate of ∼ 3.5 cm a−1. A Moho reflection has been observed at ∼ 5.5 km below the seafloor at this site, and the workshop concluded that the proposed 2.5 km deep scientific drilling on the North Arch off Hawai`i would provide an essential “pilot hole” to inform the design of future mantle drilling.

  Copernicus GmbH, Apr. 2021, Scientific Drilling, 29, 69 - 82, English

  [Refereed]

  Scientific journal


• A new miniaturized magnetometer system for long-term distributed observation on the seafloor

  K. Ogawa, T. Matsuno, H. Ichihara, K. Nakahigashi, N. Seama

  We have developed a new magnetometer system specialized to multipoint and long-term observations on the seafloor to promote marine or ocean-bottom experiments mainly for the electromagnetic sounding of the Earth's interior. In situ magnetic field observation on the seafloor is an essential geophysical technique to investigate structures of the oceanic crust and the upper mantle, many of which are still frontier as to observational evidences. The in situ and long-term observations require long-term-operable and small-size magnetometer systems, which are placed on the seafloor over a year in pressure-resistant cases without external power supply and communication. We have designed and developed a new electric circuit board of small size and lower power consumption for the magnetometer system. Our new magnetometer system, what we call "DOKODEMO MAG," is suitable to be installed in a pressure-resistant cylinder of 36 mm diameter and can operate independently over 2 years with a smaller amount of batteries than the conventional system because its power consumption was saved to similar to 33 mW. This magnetometer system is capable of observing orthogonal three-axis magnetic fields continuously with sampling frequency of 5 Hz at maximum and an accuracy of similar to 0.1 nT. The system also records tilt and temperature of the system and voltage of the batteries. Prototype models of this magnetometer system were tested for in situ operation for 5 months on the seafloor around the Kikai caldera in the south of the Kyusyu Island, SW Japan. The results of the test showed sufficient performance of our new magnetometer system and its potential of future usage for every type of marine or ocean-bottom operations.

  SPRINGEROPEN, Jul. 2018, Earth, Planets and Space, 70, 111, English

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Giant rhyolite lava dome formation after 7.3 ka supereruption at Kikai caldera, SW Japan

  TATSUMI YOSHIYUKI, SUZUKI KEIKO, MATSUNO TETSUO, HIROSHI ICHIHARA, SEAMA NOBUKAZU, KIYOSUGI KOJI, NAKAOKA REINA, NAKAHIGASHI KAZUO, H. Takizawa, KAZUKI HAYASHI, TATSURO CHIBA, SHIMIZU SATOSHI, SANO MAMORU, IWAMARU HIKARU, MOROZUMI HARUHISA, SUGIOKA HIROKO, Y. Yamamoto

  Kikai submarine caldera to the south of the Kyushu Island, SW Japan, collapsed at 7.3 ka during the latest supereruption (>500 km3 of magma) in the Japanese Archipelago. Multi functional research surveys of the T/S Fukae Maru in this caldera, including multi-beam echosounder mapping, remotely operated vehicle observation, multi-channel seismic reflection survey, and rock sampling by dredging and diving, provided lines of evidence for creation of a giant rhyolite lava dome (~32 km3) after the caldera collapse. This dome is still active as water column anomalies accompanied by bubbling from its surface are observed. Chemical characteristics of dome-forming rhyolites akin to those of presently active small volcanic cones are different from those of supereruption. The voluminous post-caldera activity is thus not caused simply by squeezing the remnant of syn-caldera magma but may tap a magma system that has evolved both chemically and physically since the 7.3-ka supereruption.

  ネイチャー・ジャパン株式会社, Feb. 2018, Scientific Reports (Nature Publishing Group), 8(1) (1), 2753 - 2753, English, International magazine

  [Refereed]

  Scientific journal

  Link to Kobe Univ. Repository (Kernel)


• Electrical resistivity structure under the western Cosmonauts Sea at the continental margin of East Antarctica inferred via a marine magnetotelluric experiment

  Tetsuo Matsuno, Yoshifumi Nogi, Nobukazu Seama

  The western Cosmonauts Sea, off the coast of East Antarctica, was a site of rifting of the Gondwana supercontinent and subsequent early seafloor spreading. To improve our understanding of the breakup of Gondwana, we conducted a marine magnetotelluric experiment to determine the electrical resistivity structure within the uppermost several hundred kilometers beneath the western Cosmonauts Sea. Magnetotelluric response functions at two sites, obtained after considering possible influences of non-plane magnetic field sources, suggest that these responses include distortions by topographic variations and conductive anomalies around the observation sites. Three-dimensional forward modeling confirmed that these distortions due to topographic variations and a thin (similar to 2-km thick) conductive layer immediately under the sites (mostly sediments) are severe. Furthermore, three-dimensional forward modeling to investigate the resistivity structure at deeper depths revealed an upper resistive layer (similar to 300 Omega-m), with a thickness of <100 km, and an underlying conductive half-space (similar to 10 Omega-m). The upper resistive layer and the underlying conductive structure most likely represent dry and water/melt-rich oceanic upper mantle, respectively. The upper resistive layer may be thinner than anticipated under the old seafloor of the study area (likely >90 Ma), and may suggest a conductive anomaly in the upper mantle produced by mantle convection and/or upwelling. (C) 2015 Elsevier B.V. and NIPR. All rights reserved.

  ELSEVIER SCIENCE BV, Jun. 2015, POLAR SCIENCE, 9(2) (2), 221 - 234, English

  [Refereed]

  Scientific journal


• The mantle dynamics, the crustal formation, and the hydrothermal activity of the southern mariana trough back-arc basin

  Nobukazu Seama, Hiroshi Sato, Yoshifumi Nogi, Kyoko Okino

  The Southern Mariana Trough back-arc basin is a currently active back arc basin, and it has fast spreading morphologic and geophysical characteristics, suggesting an additional magma supply, even though the full spreading rate is categorized as slow spreading. Five hydrothermal vent sites have been found within 5 km around the spreading axis at 13°N. The Japanese TAIGA Project selected this area as one of three integrated target sites, and TAIGA Project members conducted series of JAMSTEC research cruises for different types of geophysical surveys, together with dive observation and samplings by the submersible Shinkai 6500. We reviewed the results from these geophysical surveys and the volcanic rock samples to summarize the products from the TAIGA Project. The results provide strong constraints on the mantle dynamics and the crustal formation at the Southern Mariana Trough back-arc basin all the results support that they are influenced by hydration derived from the subducting slab with accompanying the additional magma supply. Furthermore, the results from the geophysical and geological surveys for the five hydrothermal vent sites provide characteristic features on the hydrothermal activity and the features are different between on-axis and off-axis hydrothermal sites. The on-axis hydrothermal site is associated with an episodic diking event followed by fissures in a fourth order ridge segment, and its duration and size vary depending on the episodic diking event and on the fissures following. In contrast, the formation of the off-axis hydrothermal sites is closely related to the residual heat from the volcanism rather than tectonic stresses accompanied by faults, and the off-axis hydrothermal activity is for a long period and in a large scale. We summarized all the evidence to propose our scenario of the mantle dynamics, the crustal formation, and the hydrothermal activity of the Southern Mariana Trough back-arc basin.

  Springer Japan, Jan. 2015, Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept, 2015(XVIII) (XVIII), 215 - 227, English

  [Refereed]

  In book


• Seismic structure and seismicity in the Southern Mariana trough and their relation to hydrothermal activity

  Toshinori Sato, Mariko Mizuno, Hiroyoshi Takata, Tomoaki Yamada, Takehi Isse, Kimihiro Mochizuki, Masanao Shinohara, Nobukazu Seama

  The Southern Mariana Trough is an active back-arc basin with hydrothermal activity. We investigated relations between the back-arc spreading system and the hydrothermal system in this area by conducting a seismic reflection/refraction survey and a three-month campaign of seismic observations using ocean bottom seismometers. From a 3D seismic velocity structure analysis, we mapped a low-velocity structure just beneath the spreading axis, a high-velocity structure with convex upward beneath an off-axis knoll, and a thickening of layer 2 (to about 3 km) over the refraction survey area compared with normal mid-ocean ridges. We found very low seismicity in the hydrothermal area and high seismicity in areas of high topographic relief that probably represent arc volcanoes. The low-velocity structure at the axis suggests that there is some magmatic activity beneath the axis in the form of sheetlike mantle upwellings. These may constitute the hydrothermal heat source at this site. The high-velocity structure with convex upward at the off-axis knoll suggests the presence of off-axis volcanism there. The very low seismicity suggests that this volcanism may have ceased, thus residual heat of this off-axis volcanism may contribute the heat for hydrothermal activity at this site. A comparison of the velocity structure with other back-arc spreading zones and mid-ocean ridges shows that the Southern Mariana Trough has a relatively thick layer 2 with lower seismic velocities, suggesting that the crust was formed by magmas with high volatile contents, consistent with upwelling mantle influenced by subduction. The very low seismicity at the hydrothermal sites indicates that there are no faults or fractures related to the hydrothermal activity. This suggests that the activity is not related to tectonic stresses there.

  Springer Japan, Jan. 2015, Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept, 2015(XVIII) (XVIII), 229 - 240, English

  [Refereed]

  In book


• Electrical resistivity structure of the snail site at the Southern Mariana trough spreading center

  Tetsuo Matsuno, Maho Kimura, Nobukazu Seama

  The electrical resistivity of the oceanic crust is sensitive to the porosity of the crust and the fluid temperature within crustal fractures and pores. The spatial variation of the crustal porosity and the fluid temperature that is related to a hydrothermal circulation can be deduced by revealing an electrical resistivity structure of the oceanic crust involving a hydrothermal site. We carried out a magnetometric resistivity experiment using an active source to reveal an electrical resistivity structure of the oceanic crust at the Snail site on the ridge crest of the Southern Mariana Trough. Active source electric currents were transmitted along and across the ridge axis in a 4,000 m2 area including the Snail site. Five ocean bottom magnetometers were deployed around the Snail site as receivers to measure the magnetic field induced by the transmission of the active source electric currents. The amplitude of the induced magnetic field was calculated by maximizing data density and the signal to error ratio in the data, and locations of the transmissions were determined using several types of calibration data. An optimal 1-D resistivity structure of the oceanic crust, averaged over the experimental area, was deduced by least squares from the data of the amplitude of the magnetic field and the location of the transmission. After calculating magnetic field anomalies, which are deviations of the observed amplitude from the prediction of the optimal 1-D resistivity model, an optimal 3-D resistivity structure was deduced from the magnetic field anomalies through trial and error 3-D forward modeling. The optimal 1-D resistivity structure is a two-layer model, which consists of a 5.6 Ω-m upper layer having a 1,500 m thickness and a 0.1 Ω-m underlying half-space. Using Archie’s law and porosity profiles of the oceanic crust, the resistivity of 5.6 Ω-m at depths ranging from 800 to 1,500 m suggests the presence of hightemperature fluid related to the hydrothermal circulation. The resistivity of 0.1 Ω-m below 1,500 m depth may represent a magma mush that is a heat source for the hydrothermal circulation. The optimal 3-D resistivity structure includes a conductive anomaly (0.56 Ω-m in approximately 300 m2 area down to 400 m depth) immediately below the Snail site, two resistive anomalies (56 Ω-m with slightly larger volumes than the conductive anomaly) adjacent to the conductive anomaly on the across-ridge side, and three conductive anomalies away from the Snail site. The conductive anomaly immediately below the Snail site suggests hydrothermal fluid, and the adjacent resistive anomalies suggest areas of low porosity. The size and distribution of the conductive and resistive anomalies near the Snail site constrains the size and style of the hydrothermal circulation.

  Springer Japan, Jan. 2015, Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept, 2015(XVIII) (XVIII), 241 - 251, English

  [Refereed]

  In book


• Asymmetric seafloor spreading of the southern mariana trough back-arc basin

  Nobukazu Seama, Kyoko Okino

  We compiled multi-narrow beam bathymetric data and geomagnetic field data obtained by a series of JAMSTEC research cruises in the SouthernMariana Trough back-arc basin, where is selected as one of three integrated target sites for the Japanese TAIGA Project. The bathymetric data are used to trace the non-transform offsets that define the ridge segments at the off-axis, and to characterize the seafloor morphology signatures from the bathymetry profiles across the spreading axes of two ridge segments. The geomagnetic field data are used to derive the crustal magnetization distribution and to estimate the spreading rate of the southern segment. Both of the spreading rate and the seafloor deepening rate of the southern segment support highly asymmetric seafloor spreading much faster spreading in the west side of the spreading axis compared to the east side (trench side).We estimated the full spreading rate as 46 km/Myr with its half rate of 33 km/Myr for thewest side and 13 km/Myr for the east side. In contrast to the southern segment, our results indicate that the northern segment has a different style of the asymmetric seafloor spreading that is accompanied by an obvious trace of a ridge jump to the trench side. The local symmetry axis in the bathymetry profiles locates at a distance of 18 km to the west fromthe spreading axis, suggesting that it is the failed spreading axis due to the ridge jump. The location of this failed spreading axis coincides with the center of the bull’s eye feature in the Mantle Bouguer anomaly, suggesting that the ridge jump to the trench side with an increase in the magma supply. We propose that the influence of the low viscosity region in the mantle wedge due to hydration driven by water release from the subducting slab leads to the highly asymmetric seafloor spreading the low viscosity mantle would preferentially captures the mantle upwelling zone beneath the spreading axis as the spreading axis has been kept in the area closed to the lowviscosity region in themantlewedge, resulting in the highly asymmetric seafloor spreading. Further, the different styles of the asymmetric seafloor spreading between the northern segment and the southern segment probably show evidence that the influence varies with the distance from the low viscosity region in the mantle wedge.

  Springer Japan, Jan. 2015, Subseafloor Biosphere Linked to Hydrothermal Systems: TAIGA Concept, 2015(XVIII) (XVIII), 253 - 260, English

  [Refereed]

  In book


• Hydrothermal heat mining in an incoming oceanic plate due to aquifer thickening: Explaining the high heat flow anomaly observed around the Japan Trench

  Yoshifumi Kawada, Makoto Yamano, Nobukazu Seama

  To explain the origin of a high heat flow anomaly observed within 150 km seaward of the Japan Trench, we construct a thermal model for an oceanic plate prior to subduction that includes the effect of hydrothermal circulation within a high-permeability aquifer in its uppermost part. The model includes the effects of aquifer thickening, which is expected to occur near subduction zones where plate bending prior to subduction causes fracturing and faulting within the oceanic plate. Using typical parameter values for the Japan Trench, we find that hydrothermal circulation in the thickening aquifer mines heat from the underlying basement and can account for the observed high heat flow anomaly. The ratio of heat supply below the aquifer as a result of aquifer thickening to the inverse of the thermal resistance of the sediment layer is a control parameter for the system. As long as the aquifer permeability is higher than approximate to 10(-13) m(2), a typical value for the uppermost part of the oceanic plate, variations in other details of the hydrothermal circulation such as the exact value of the aquifer permeability and the size of the convection cells do not significantly change model results. Despite its strong influence on seafloor heat flow seaward of the trench, this hydrothermal heat mining does not affect significantly the thermal structure of the subducted oceanic plate. This finding indicates that surface heat flow anomaly around the trench may not correspond to temperature anomaly within the subducted oceanic plate and the megathrust seismogenic zone.

  AMER GEOPHYSICAL UNION, Apr. 2014, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 15(4) (4), 1580 - 1599, English

  [Refereed]

  Scientific journal


• Magmatic activities on the Southwest Indian Ridge between 35 degrees E and 40 degrees E, the closest segment to the Marion hotspot

  Taichi Sato, Kyoko Okino, Hiroshi Sato, Mariko Mizuno, Tomoko Hanyu, Nobukazu Seama

  We conducted geophysical surveys, including bathymetry, gravity, and magnetism, within a first-order segment of the Southwest Indian Ridge (SWIR) between the Prince Edward and Eric Simpson fracture zones (FZs) (latitude 35 degrees-40 degrees E, segment PE), in the vicinity of the Marion hotspot. Segment PE includes four orthogonally spreading second-order segments (PE-1, PE-2, PE-3, and PE-4) and a long, oblique axial valley (NTD-1). Segments PE-1, PE-2, and PE-4 are magmatic, whereas segment PE-3 and NTD-1 are characterized by low magmatic activity. Segment PE-3 is a nascent segment and NTD-1 contains three tiny magmatic sections. Each low-magmatic interval along the axis of segment PE lies between two magmatic segments. This segmentation pattern is similar to the SWIR between the Gallieni and Melville FZs; therefore, a strong melt-focusing process can be expected. Different characteristics of second-order magmatic segments suggest that the magmatic activity in each segment varies among each other as well as that of the other segments of SWIR. Continuous seafloor morphology and isochrons over off-axis areas of segment PE-1 and NTD-1 suggest that PE-1 shortened after the C2An chron. The V-shaped bathymetric structure between segment PE-1 and NTD-1 suggests that the melt supply center has migrated westward. This westward melt migration would have reduced magmatic activity at NTD-1 after C2An. Ridge obliquity may also have reduced magmatic activity. Geophysical characteristics of second-order segments suggest that magmatic activity of segment PE is mainly controlled by a strong melt-focusing process and a comparatively low contribution of melt supply from Marion hotspot.

  AMER GEOPHYSICAL UNION, Dec. 2013, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 14(12) (12), 5286 - 5307, English

  [Refereed]

  Scientific journal


• A continuously towed vertical bipole source for marine magnetometric resistivity surveying

  Nobukazu Seama, Noriko Tada, Tada-nori Goto, Masashi Shimoizumi

  We propose to use an approximately vertical bipole electric current towed by a ship as a source for a Magnetometric Resistivity (MMR) method. This proposal requires the precise positioning of the bottom electrode for the bipole source, and our newly developed MMR system achieved this. We conducted an MMR experiment in the central Mariana Trough, and we obtained data using two different methods along a survey line: one method towed a bipole source transmitting continuously along the survey line, and the other used a conventional vertical bipole source transmitting at several stationary transmission stations along the survey line. We found that the towed bipole source tilted from the vertical by an angle of 8 degrees at the maximum during the MMR experiment. We compared the results from the two methods to evaluate the towed bipole source method. Our results indicate that the tilted bipole source approximates well with the vertical bipole source at the mid-point between the surface and the bottom electrodes. Since the towed bipole source method requires much less survey time and the results show a higher spatial resolution, it is a powerful tool for MMR experiments to image a shallow oceanic crustal resistivity structure efficiently.

  TERRA SCIENTIFIC PUBL CO, 2013, EARTH PLANETS AND SPACE, 65(8) (8), 883 - 891, English

  [Refereed]

  Scientific journal


• Electromagnetic constraints on a melt region beneath the central Mariana back-arc spreading ridge

  Tetsuo Matsuno, Rob L. Evans, Nobukazu Seama, Alan D. Chave

  An electrical resistivity profile across the central Mariana subduction system shows high resistivity in the upper mantle beneath the back-arc spreading ridge where melt might be expected to exist. Although seismic data are equivocal on the extent of a possible melt region, the question arises as to why a 2-D magnetotelluric (MT) survey apparently failed to image any melt. We have run forward models and inversions that test possible 3-D melt geometries that are consistent with the MT data and results of other studies from the region, and that we use to place upper bounds on the possible extent of 3-D melt region beneath the spreading center. Our study suggests that the largest melt region that was not directly imaged by the 2-D MT data, but that is compatible with the observations as well as the likely effects of melt focusing, has a 3-D shape on a ridge-segment scale focused toward the spreading center and a resistivity of 100 Omega-m that corresponds to similar to 0.1-similar to 1% interconnected silicate melt embedded in a background resistivity of similar to 500 Omega-m. In contrast to the superfast spreading southern East Pacific Rise, the 3-D melt region suggests that buoyant mantle upwelling on a ridge-segment scale is the dominant process beneath the slow-spreading central Mariana back-arc. A final test considers whether the inability to image a 3-D melt region was a result of the 2-D survey geometry. The result reveals that the 2-D transect completed is useful to elucidate a broad range of 3-D melt bodies.

  AMER GEOPHYSICAL UNION, Oct. 2012, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 13(10) (10), Q10017, English

  [Refereed]

  Scientific journal


• The role of seamounts in the transport of heat and fluids: Relations among seamount size, circulation patterns, and crustal heat flow

  Yoshifumi Kawada, Nobukazu Seama, Tetsuro Urabe

  To evaluate the role of seamounts in the transport of heat and fluids, we performed numerical simulations of hydrothermal circulation within and around seamounts that protrude through low-permeability sedimentary layers. A cylindrical flat-top seamount model enables us to take into account crustal heat flow, and the radius and height (i.e., the radius/height ratio) of the seamount. We found that the flow patterns depend primarily on the aspect ratio of the seamount, and secondarily on crustal heat flow. A large seamount, with a radius of several tens of kilometers, cools itself by convection cells that form within the seamount, and this behavior is independent of crustal heat flow. In contrast, a small seamount, with a radius of several hundreds of meters, works as a fluid passageway, either as a fluid exit by discharging hydrothermal fluids at low crustal heat flows, or as a fluid entrance by recharging seawater at high crustal heat flows. The role of a medium-sized seamount varies according to crustal heat flow: it is cooled by a convection cell at low heat flows and works as a fluid entrance at high heat flows. We also found that an increase in crustal heat flow has the same effect on the fluid flow pattern as does an increase in seamount permeability or sediment thickness. (C) 2011 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Jun. 2011, EARTH AND PLANETARY SCIENCE LETTERS, 306(1-2) (1-2), 55 - 65, English

  [Refereed]

  Scientific journal


• Upper mantle electrical resistivity structure beneath the central Mariana subduction system

  Tetsuo Matsuno, Nobukazu Seama, Rob L. Evans, Alan D. Chave, Kiyoshi Baba, Antony White, Tada-nori Goto, Graham Heinson, Goran Boren, Asami Yoneda, Hisashi Utada

  This paper reports on a magnetotelluric (MT) survey across the central Mariana subduction system, providing a comprehensive electrical resistivity image of the upper mantle to address issues of mantle dynamics in the mantle wedge and beneath the slow back-arc spreading ridge. After calculation of MT response functions and their correction for topographic distortion, two-dimensional electrical resistivity structures were generated using an inversion algorithm with a smoothness constraint and with additional restrictions imposed by the subducting slab. The resultant isotropic electrical resistivity structure contains several key features. There is an uppermost resistive layer with a thickness of up to 150 km beneath the Pacific Ocean Basin, 80-100 km beneath the Mariana Trough, and 60 km beneath the Parece Vela Basin along with a conductive mantle beneath the resistive layer. A resistive region down to 60 km depth and a conductive region at greater depth are inferred beneath the volcanic arc in the mantle wedge. There is no evidence for a conductive feature beneath the back-arc spreading center. Sensitivity tests were applied to these features through inversion of synthetic data. The uppermost resistive layer is the cool, dry residual from the plate accretion process. Its thickness beneath the Pacific Ocean Basin is controlled mainly by temperature, whereas the roughly constant thickness beneath the Mariana Trough and beneath the Parece Vela Basin regardless of seafloor age is controlled by composition. The conductive mantle beneath the uppermost resistive layer requires hydration of olivine and/or melting of the mantle. The resistive region beneath the volcanic arc down to 60 km suggests that fluids such as melt or free water are not well connected or are highly three-dimensional and of limited size. In contrast, the conductive region beneath the volcanic arc below 60 km depth reflects melting and hydration driven by water release from the subducting slab. The resistive region beneath the back-arc spreading center can be explained by dry mantle with typical temperatures, suggesting that any melt present is either poorly connected or distributed discontinuously along the strike of the ridge. Evidence for electrical anisotropy in the central Mariana upper mantle is weak.

  AMER GEOPHYSICAL UNION, Sep. 2010, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 11(9) (9), Q09003, English

  [Refereed]

  Scientific journal


• The mohole: A crustal journey and mantle quest, workshop in Kanazawa, Japan, 3-5 June 2010

  Benoît Ildefonse, Natsue Abe, Donna K. Blackman, J. Pablo Canales, Yoshio Isozaki, Shuichi Kodaira, Greg Myers, Kentaro Nakamura, Mladen Nedimovic, Alexander C. Skinner, Nobukazu Seama, Eiichi Takazawa, Damon A.H. Teagle, Masako Tominaga, Susumu Umino, Douglas S. Wilson, Masaoki Yamao

  Sep. 2010, Scientific Drilling, 10, 56-63(10) (10), 56 - 63, English

  [Refereed]

  Scientific journal


• Review of Oceanic Crustal Structure and Seafloor Hydrothermal Circulation

  Yoshifumi KAWADA, Nobukazu SEAMA, Kyoko OKINO

  Tokyo Geographical Society, 2009, Chigaku Zasshi (Jounal of Geography), 118(6) (6), 1037 - 1063, Japanese

  [Refereed]

  Scientific journal


• A marine deep-towed DC resistivity survey in a methane hydrate area, Japan Sea

  Tada-nori Goto, Takafumi Kasaya, Hideaki Machiyama, Ryo Takagi, Ryo Matsumoto, Yoshihisa Okuda, Mikio Satoh, Toshiki Watanabe, Nobukazu Seama, Hitoshi Mikada, Yoshinori Sanada, Masataka Kinoshita

  We have developed a new deep-towed marine DC resistivity survey system. It was designed to detect the top boundary of the methane hydrate zone, which is not imaged well by seismic reflection surveys. Our system, with a transmitter and a 160-m-long tail with eight source electrodes and a receiver dipole, is towed from a research vessel near the seafloor. Numerical calculations show that our marine DC resistivity survey system can effectively image the top surface of the methane hydrate layer. A survey was carried out off Joetsu, in the Japan Sea, where outcrops of methane hydrate are observed. We successfully obtained DC resistivity data along a pro. le similar to 3.5 km long, and detected relatively high apparent resistivity values. Particularly in areas with methane hydrate exposure, anomalously high apparent resistivity was observed, and we interpret these high apparent resistivities to be due to the methane hydrate zone below the seafloor. Marine DC resistivity surveys will be a new tool to image sub-seafloor structures within methane hydrate zones.

  CSIRO PUBLISHING, Mar. 2008, EXPLORATION GEOPHYSICS, 39(1) (1), 52 - 59, English

  [Refereed]

  Scientific journal


• 1-D electrical conductivity structure beneath the Philippine Sea: Results from an ocean bottom magnetotelluric survey

  Nobukazu Seama, Kiyoshi Baba, Hisashi Utada, Hiroaki Toh, Noriko Tada, Masahiro Ichiki, Tetsuo Matsuno

  Eight-months of observation using Ocean Bottom Electro-Magnetometers (OBEMs) have allowed us to estimate the regional electrical conductivity structure beneath the Philippine Sea. Six OBEMs were deployed along a line crossing the Philippine Sea from NW to SE and five of them recorded useful data. The raw time series data were cleaned up before we estimated the magnetotelluric (MT) impedance tensor. Conductivity structure at five sites is estimated using 1-D Occam's inversion to fit the determinant average of each MT impedance tensor after a correction for the effect of topography. We examined effect from two dimensionalities on the 1-D conductivity structure and the robustness of solutions. The results of the 1-D conductivity structural model are strongly related to tectonic setting and the crustal age beneath each site. The structure beneath the spreading axis of the Mariana Trough shows a distinct low conductivity structure at depths of 50-150 km and it probably reflects the upwelling dynamics operating beneath the spreading axis. These low values are comparable with that of olivine with low hydrogen content, implying that (1) the melting process extracts water from minerals such as olivine, and (2) the melt beginning depth in the Mariana Trough is deeper than that of the typical MORB source region. The off-axis conductivity profiles infer the existence of a high conductivity peak or a conductivity gradient change at mid-depth. The depth level of the peak increases with crustal age, suggesting that the conductivity structure is related to a geothermal structure and that these conductivity profiles are explained by the temperature gradient change, possibly combined with the presence of partial melt. Our results suggest that further ocean bottom EM study has high potential to investigate the temperature gradient change and amount of hydrogen (water) and melt in the upper mantle. (c) 2007 Elsevier B.V. All rights reserved.

  ELSEVIER SCIENCE BV, Jun. 2007, PHYSICS OF THE EARTH AND PLANETARY INTERIORS, 162(1-2) (1-2), 2 - 12, English

  [Refereed]

  Scientific journal


• A study on correction equations for the effect of seafloor topography on ocean bottom magnetotelluric data

  Tetsuo Matsuno, Nobukazu Seama, Kiyoshi Baba

  Consideration of the effect of seafloor topography on ocean bottom magnetotelluric data is needed to estimate a reliable resistivity structure. Selection of the correction equation which precisely takes account of distortions is important when we correct the effect of seafloor topography with forward modeling. Corrections of synthetic data based on three different correction equations are carried out, and the corrected responses and the true response are compared to investigate which correction equation is the best in application to distorted magnetotelluric data on the seafloor. Differences in the corrected responses are remarkable at periods shorter than several thousands seconds. These differences are caused by differences in treatment of the distortions of magnetic field and in robustness of the correction equation to a resistivity structure assumed for the topographic correction. The results suggest that the correction equation of Nolasco et al. (1998) should be used because it better accommodates the estimation of unknown resistivity structures. We apply the correction equation of Nolasco et al. (1998) to a response observed in the Mariana area. The one-dimensional resistivity structure estimated from the corrected response explains almost all the components of the observed response.

  TERRA SCIENTIFIC PUBL CO, 2007, EARTH PLANETS AND SPACE, 59(8) (8), 981 - 986, English

  [Refereed]

  Scientific journal


• Distinct regional differences in crustal thickness along the axis of the Mariana Trough, inferred from gravity anomalies

  K Kitada, N Seama, T Yamazaki, Y Nogi, K Suyehiro

  [ 1] We have compiled extensive gravity and bathymetry data for the whole Mariana Trough, which were collected during several Japanese scientific cruises over the last few years. This study aims to clarify the lateral distribution of the local differences in geochemical signatures, which have been observed locally in the Mariana Trough. Shipboard free-air gravity anomaly data from eight Japan Agency for Marine-Earth Science and Technology (JAMSTEC) cruises were compiled with those crossover errors of 2.85 mgal. Mantle Bouguer anomalies (MBA) were calculated by subtracting the predictable gravity signal due to the seawater/crust and crust/mantle density boundaries. The crustal thickness variation along the spreading axis was estimated from the MBA. Different features in crustal thickness, its variation, and segment length for each segment, allow us to identify four distinct regional differences in magmatic activity along the spreading axis of the Mariana Trough. Segment in region A ( to the north of 20 degrees 35'N) shows the largest sectional dimensions of crust along the axis and it is probably affected by an additional supply from island arc magma sources. A variety of crustal thickness values and of along-axis crustal thickness variations in region B ( between 15 degrees 38'N and 20 degrees 35'N) suggests two types of segments. One is similar to a slow spreading ridge segment that has a plume-like mantle upwelling under the spreading axis, and the other is a magma-starved segment. Region C ( between 14 degrees 22'N and 15 degrees 38'N) is a less magmatic region ( individual crustal thickness averages of 3.4 - 4.1 km). Region D ( to the south of 14 degrees 22'N) has higher individual crustal thickness averages of 5.9 - 6.9 km, suggesting higher magmatic activity with a sheet-like mantle upwelling under the spreading axis. Different features in the MBA for off-axis areas suggest that these four regions have existed since the Mariana Trough started spreading. Moreover, comparison between our results of crustal thickness and previous geochemical results indicates that less magmatic spreading segments with thin crust, which are locally distributed in both regions B and C, probably result from mantle source depleted of water and incompatible elements. This suggests that lateral compositional variation of water and incompatible elements exists on a segment scale in the mantle source beneath the spreading axis of the Mariana Trough.

  AMER GEOPHYSICAL UNION, Apr. 2006, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 7, English

  [Refereed]

  Scientific journal


• Measurements by Ocean Bottom Gravimeter at Harima-nada in Seto Inland Sea, Japan.

  JYOSHIMA M, ISHIHARA T, KOIZUMI K, SEAMA N, OSHIDA A, FUJIMOTO H, KANAZAWA T

  海洋調査技術学会, 2006, Journal of Japan Society for Marine Surveys and Technology, 18(1), 17-27(1) (1), 17 - 27, Japanese

  [Refereed]

  Scientific journal


• 1-D resistivity structures of the oceanic crust around the hydrothermal circulation system in the central Mariana Trough using Magnetometric Resistivity method

  Noriko Tada, Nobukazu Seama, Tada-nori Goto, Motoyuki Kido

  Abstract We present preliminary results of an electromagnetic survey over a region of hydrothermal circulation in the spreading axis of the central Mariana Trough. The Magnetometric Resistivity (MMR) method is used to determine the electrical resistivity structure of the oceanic crust around the hydrothermal system. 1-D electrical resistivity structure is calculated from the relation between the amplitude of magnetic field and source-receiver separation. The amplitudes of magnetic field variation of ocean bottom magnetometers (OBMs) placed on axis are larger than those of OBMs about 700 m away from the spreading axis, for source-receiver separations larger than 400 m. We estimated two resistivity structure models: one for the axial OBMs, and another for the off-axis OBMs. A region of lower resistivity between depths of 100–300 m is identified in the on-axis model. The hydrothermal source of the Alice Springs Field probably exists beneath the spreading axis, and the size of this source is smaller than 700 m. Lower resistivities at a depth of 50 m are identified in both the on-axis and the off-axis models, suggesting that the porosity in the uppermost oceanic crust is largest at this depth.

  Springer Science and Business Media LLC, Jul. 2005, Earth, Planets and Space, 57(7) (7), 673 - 677

  Scientific journal


• Geomagnetic paleointensity over 1.2 Ma from deep-tow vector magnetic data across the East Pacific Rise

  Michiko Yamamoto, Nobukazu Seama, Nobuhiro Isezaki

  Abstract Deep-tow vector magnetic data have been acquired across the fast-spreading southern East Pacific Rise 18°S and inverted to magnetization intensity variations. Vector magnetic data are used to determine continuous magnetic intensity within intervals of constant polarity over the Matuyama and Brunhes periods up to the Cobb Mountain event at 1.19 Ma. A comparison of our deep-tow vector data and a sediment core-derived geomagnetic paleointensity timescale suggests that the short-wavelength magnetic anomaly signal is indeed of geomagnetic origin and can be used to date the seafloor with a high resolution. The crustal age determined from our date reveals a highly asymmetric spreading rate for the recent period (since 0.3 Ma).

  Springer Science and Business Media LLC, May 2005, Earth, Planets and Space, 57(5) (5), 465 - 470

  [Refereed]

  Scientific journal


• 水曜海山の地球物理学的構造と海底熱水循環系

  SEAMA Nobukazu, NISIZAWA Azusa, KAWATA K

  Surface geophysical, airgun-OBS (ocean bottom seismograph), and deep-towed surveys by R/V Kairei KR01-15 cruise, and OBS array observations were conducted to characterize geophysical features of a hydrothermal system in Suiyo Seamount as a part of Archaean Park Project. Geomagnetic results from surface and deep towed magnetometers suggest 1) the seamount was formed during Brunhes Epoch (after 0.78 My), and 2) a low magnetization area exists on its summit and is limited only on the eastern side with a diameter of 800 meters. 2-D ray tracing results, using four OBS data with a GI gun across the seamount in NE-SW direction, indicate that a P wave velocity of 2.2∿4.2 km s^-1 (2 km thickness) is located all over the observation line. The OBS array observations reveal the seismic activity and the hypocenter determination indicates that the locations of these earthquakes are focused in a chimney-like shape within its diameter of 3 km just beneath the Suiyo volcanic cone at a depth of 3∿7km. We propose a model to explain these geophysical observations; the former main conduit of Suiyo Seamount is in the middle of cooling after the last eruption, and its heat drives the hydrothermal system in Suiyo Seamount. We perform a numerical simulation of a magma injection in the conduit with its diameter of 1 km and its cooling process has two different mechanisms; 1) a major hydrothermal circulation exists in the uppermost crust with P wave velocity of 2.2∿4.2 km s^-1 (2 km thickness), suggesting a higher porosity region, and 2) thermal conduction is dominated in the deeper part. In the thermal conduction region, the existence of a cooling area inside and a heating area outside near the former main conduit leads to thermal differential stress, which is the cause of earthquakes below a depth of 3 km. This is a reasonable explanation of chimney-like shape hypocenter locations. The magma injection in the conduit with its diameter of 1 km has enough heat to drive hydrothermal circulation at least for a few hundreds years and the hydrothermal circulation is maintained for long times enough to make the low magnetization area with its diameter of 800 meters through the high alteration of the rock. This stable existence of the hydrothermal system in Suiyo Seamount would be an important factor to discuss regarding the origin and evolution of subsurface-vent biospheres, especially when the hydrothermal system has been isolated.

  The Oceanographic Society of Japan, 2005, 海の研究, 14(2), 139-150(2) (2), 139 - 150, Japanese

  [Refereed]

  Scientific journal


• 海洋地磁気異常は何を映すか？－地磁気異常と古地磁気強度変化の関連－

  YAMAMOTO M, SEAMA Nobukazu

  Paleomagnetic intensity variation through marine magnetic anomalies could provide the finest time-depended information on plate tectonics. Rapid progress in the study of marine magnetic anomalies at the mid-ocean ridge area and developments in observation techniques have revealed a link between magnetic anomalies and paleomagnetic intensity variation. Combining recent high-resolution magnetic anomaly data from sea-bottom surveys and sediment-derived paleomagnetic intensity variations has played a key role in providing hope to the hypothesis attributing "tiny wiggle" in marine magnetic anomalies to the paleomagnetic field. However, this does not mean that the other competing hypothesis based on the variation of magnetic layer thickness instead of paleomagnetism, is ruled out. More data and higher analytic techniques would narrow down these possible sources. We introduce some significant steps to the evidences of the paleomagnetic field in magnetic anomalies along with history that sea-going geophysicists have piled up, including the development of instrument and magnetic structure models, and a shift in interpreting magnetic signals as geochemistry of the extrusive rocks, bathymetry expression, low-temperature alteration of basalt by fissuring and cracking, weathering by oxidation with age and the variation of magnetic layer thickness.

  Tokyo Geographical Society, 2005, 地学雑誌, 114(2)、239-249(2) (2), 239 - 249, Japanese

  [Refereed]

  Scientific journal


• 「アーキアン・パーク計画」が明らかにしたもの

  浦辺 徹郎, 丸山 明彦, 丸茂 克美, SEAMA Nobukazu, 石橋 純一郎

  The Archaean Park Project, which is funded by Special Coordination Fund of the Ministry of Education, Science and Technology (MEXT) is a major program to analyze the interaction between the sub-vent biosphere and the geosphere of the seafloor hydrothermal system. The convection of hydrothermal fluid within the oceanic crust gives rise to various sub-surface environments near hydrothermal vents. Such environmental conditions are analogous to the site of origin and/or early evolution of life during the Archaean age. Since the Domain Bacteria and Domain Archaea near the root of the Universal Tree are hyper-thermophilic, we named our proposal the "Archaean Park Project". There are four sub-themes in the project; 1) Physical processes of hydrothermal circulation systems, 2) Observation of the chemical environment of the sub-vent biosphere, 3) Microbiology and molecular ecology in the sub-vent biosphere; and 4) Interaction between microbial and geological processes. Here, we summarize the results of the research mainly performed in the first three-year period in terms of the deep-sea hydrothermal system at Suiyo Seamount, Izu-Bonin arc (Ogasawara arc), western Pacific.

  The Oceanographic Society of Japan, 2005, 海の研究, 14(2) (2), 129 - 137, Japanese

  [Refereed]

  Scientific journal


• An interpretation of the seafloor spreading history of the West Enderby Basin between initial breakup of Gondwana and anomaly C34

  Y Nogi, K Nishi, N Seama, Y Fukuda

  The seafloor spreading evolution in the Southern Indian Ocean is key to understanding the initial breakup of Gondwana. We summarize the structural lineaments deduced from the GEOSAT 10 Hz sampled raw altimetry data as well as satellite derived gravity anomaly map and the magnetic anomaly lineation trends from vector magnetic anomalies in the West Enderby Basin, the Southern Indian Ocean. The gravity anomaly maps by both Sandwell and Smith 1997, J. Geophys. Res. 102, 10039-10054 and 10 Hz raw altimeter data show almost the same general trends. However, curved structural trends, which turn from NNW-SSE in the south to NNE-SSW in the north, are detected only from gravity anomaly maps by 10 Hz raw altimeter data just to the east of Gunnerus Ridge. NNE-SSW structural trends and magnetic anomaly lineation trends that are perpendicular to them are observed between the Gunnerus Ridge and the Conrad Rise. To the west of Gunnerus Ridge, structural elements trend NNE-SSW and magnetic polarity changes are normal to them. In contrast, almost NNW-SSE structural trends and ENE-WSW magnetic polarity reversal strikes are dominant to the east of Gunnerus Ridge. Curved structural trends, which turn from WNW-ESE direction in the south to NNE-SSW direction in the west, and magnetic polarity reversal strikes that are almost perpendicular to them are observed just south of Conrad Rise. The magnetic polarity reversals may be parts of the Mesozoic magnetic anomaly sequence that formed along side of the structural lineaments before the long Cretaceous normal polarity superchron. Curved structural trends, detected only from gravity anomaly maps by 10 Hz raw altimeter data, most likely indicate slight changes in spreading direction from an initial NNW-SSE direction to NNE-SSW. Our results also suggest that these curved structural trends are fracture zones that formed during initial breakup of Gondwana.

  SPRINGER, Sep. 2004, MARINE GEOPHYSICAL RESEARCHES, 25(3-4) (3-4), 221 - 231, English

  [Refereed]

  Scientific journal


• Genetic Algorithm inversion of geomagnetic vector data using a 2.5-dimensional magnetic structure model

  M Yamamoto, N Seama

  We propose a new inversion method for vector magnetic field data, which uses the Genetic Algorithm in a space domain calculation to determine the best-fitting 2.5-dimensional (2.5-D) structure. This 2.5-D model is composed of magnetic boundaries with arbitrary strike and magnetic intensity. Two numerical formulas combine to express this model. One of them is a two-dimensional magnetic structure expression for a realistically shaped magnetic layer, and the other is a magnetization contrast expression for magnetic boundaries of variable strike. We use a Genetic Algorithm as the computational technique that supports optimum solutions for magnetization, magnetic strike, and boundary location. In practice, calculations are more accurate in the space domain instead of the more conventional frequency domain because it better preserves the short wavelength components and the true geometry between magnetic sources and observation points even for uneven survey track lines. The above leads to high resolution in the inferred magnetization without the need of upward continuation, which is particularly useful for inverting near-bottom survey data. The code is designed to use smaller storage and less computational time. Its application to synthetic data illustrates the power of resolution and precision in interpreting the fine scale processes of mid-ocean ridge accretion.

  SPRINGER HEIDELBERG, 2004, Earth, Planets and Space, 56(2) (2), 217 - 227, English

  [Refereed]

  Scientific journal


• Discovery of a new hydrothermal venting site in the southernmost Mariana Arc: Al-rich hydrothermal plumes and white smoker activity associated with biogenic methane

  T Gamo, H Masuda, T Yamanaka, K Okamura, J Ishibashi, E Nakayama, H Obata, K Shitashima, Y Nishio, H Hasumoto, M Watanabe, K Mitsuzawa, N Seama, U Tsunogai, F Kouzuma, Y Sano

  This paper reports a series of studies leading to the discovery of a submarine hydrothermal field (called Nakayama Field) at an arc seamount (12degrees43' N, 143degrees32' E) in the southernmost part of the Mariana Trough, western Pacific Ocean. We first detected hydrothermal plumes characterized by water column anomalies of temperature, light transmission, Mn, Fe, Al, O-2, CH4, and delta(13)C of CH4 above the summit caldera of the seamount. Then deep-tow camera surveys confirmed the existence of hydrothermal activity inside the caldera, and an ROV dive finally discovered white smoker-type fluid venting associated with vent fauna. A high concentration of aluminum in the plume and white smoker-type emissions imply acidic hydrothermal activity similar to that observed at the DESMOS Caldera in the eastern Manus Basin, Papua New Guinea. Anomalously low delta(13)C (CH4) of -38parts per thousand of a vent fluid sample compared to other arc hydrothermal systems along the Izu-Bonin and Mariana Arcs suggests an incorporation of biogenic methane based on a subsurface microbial ecosystem.

  GEOCHEMICAL SOC JAPAN, 2004, GEOCHEMICAL JOURNAL, 38(6) (6), 527 - 534, English

  [Refereed]

  Scientific journal


• Spreading process of the northern Mariana Trough: Rifting-spreading transition at 22 degrees N

  T Yamazaki, N Seama, K Okino, K Kitada, J Naka

  [1] We have conducted a geophysical survey of the northern Mariana Trough from 19degreesN to 24degreesN. The trough evolves southward from incipient rifting to seafloor spreading within this region. This study aims to clarify the location and time of the rifting-to-spreading transition, which was controversial previously, and processes of seafloor spreading after the transition. The new data set includes swath bathymetry with side-scan images and magnetic vector anomaly. The mantle Bouguer gravity anomaly (MBA) was calculated using the free-air gravity anomaly from satellite altimetry. The rifting-to-spreading transition occurs at about 22degreesN, which is proved by seafloor-spreading fabric in the bathymetry, clear magnetic lineations, and the bull's-eye pattern in MBA. Four ridge segments separated by three nontransform discontinuities are recognized between 19 N and 22 N. The northernmost segment has relatively abundant magma supply compared with the other segments, which is estimated from a larger segment length, shallower axial depths with no rift valley, and lower MBA. The next segment to the south is, on the other hand, a magma-starved segment with a prominent rift valley. Two anomalously deep grabens (called the Central Grabens) formed by amagmatic extension occur near the segment ends. The succession of magma-rich, magma-starved, and normal segments with increasing distance from the volcanic arc is the same as the observation in the Lau Basin reported by Martinez and Taylor [2002]. The magnetic anomaly revealed the detailed history of the spreading. The seafloor spreading between 19degreesN and 20degreesN began prior to 5 Ma, and that between 20degreesN and 21degrees30'N began at about 4 Ma. Spreading half-rates in the western side of the spreading center were 2 to 3 cm/year before 2.58 Ma south of 21degrees30'N and during the Matuyama Chron north of 21degrees30'N, but an average during the Brunhes Chron is 1 cm/year or less. Orientations of the ridge axes, which range from -20degrees to 0degrees at present, have rotated about 20degrees clockwise since the start of the spreading. These changes in rate and direction might be associated with changes in the motion of the Philippine Sea plate. Spreading has been asymmetric in the northern Mariana Trough. The spreading rates of the western side of the spreading center have been significantly larger than the eastern counterpart in general. The asymmetry may have been caused by an interaction of mantle upwelling systems under the volcanic front and the backarc spreading center and would be a characteristic of backarc spreading.

  AMER GEOPHYSICAL UNION, Sep. 2003, GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS, 4, English

  [Refereed]

  Scientific journal


• 海洋調査フロンティア増補版第5章－近年の海洋における地球物理観測技術の進歩

  島 伸和, 松林 修

  2003, Jour.Japan Soc.Mar.Surv.Tech., 15,71-87, Japanese

  Scientific journal


• A new technique for the incorporation of seafloor topography in electromagnetic modelling

  K Baba, N Seama

  We describe a new technique for incorporating seafloor topography in electromagnetic modelling. It is based on a transformation of the topographic relief into a change in electrical conductivity and magnetic permeability within a flat seafloor. Since the technique allows us to model arbitrary topographic changes without extra grid cells and any restriction by vertical discretization, we can model very precise topographic changes easily without an extra burden in terms of computer memory or calculation time. The reliability and stability of the technique are tested by comparing the magnetotelluric responses from two synthetic seafloor topography models with three different approaches; these incorporate the topographic change in terms of (1) the change in conductance, using the thin-sheet approximation; (2) a series of rectangular block-like steps; and (3) triangular finite elements. The technique is easily applied to any modelling method including 3D modelling, allowing us to model complex structure in the Earth while taking full account of the 3D seafloor topography.

  BLACKWELL PUBLISHING LTD, Aug. 2002, GEOPHYSICAL JOURNAL INTERNATIONAL, 150(2) (2), 392 - 402, English, International magazine

  [Refereed]

  Scientific journal


• Study on deep crustal structure of the Ulleung Basin, the East Sea (Japan Sea), from separating shallow components of gravity anomalies

  Park, C.H, N. Isezaki, N. Seama, H. Shon, J.W. Kim

  2002, Journal of the Geological Society of Korea, 38(4) (4), 519 - 535

  [Refereed]

  Scientific journal


• Basement orientation in the East Enderby Basin, Southern Indian Ocean

  Nogi, Y, Seama, N

  2002, Antarctica at the close of a millennium, The Royal Society of New Zealand, 35, 539-547

  [Refereed]


• Global superconducting gravimeter observations and the search for the translational modes of the inner core

  N. Courtier, B. Ducarme, J. Goodkind, J. Hinderer, Y. Imanishi, N. Seama, H. Sun, J. Merriam, B. Bengert, D.E. Smylie

  Elsevier BV, Jan. 2000, Physics of the Earth and Planetary Interiors, 117(1-4) (1-4), 3 - 20

  Scientific journal


• Asymmetric Electrical Structure in the Mantle Beneath the East Pacific Rise at 17°S

  R. L. Evans, P. Tarits, A. D. Chave, A. White, G. Heinson, J. H. Filloux, H. Toh, N. Seama, H. Utada, J. R. Booker, M. J. Unsworth

  The magnetotelluric component of the Mantle Electromagnetic and Tomography (MELT) Experiment measured the electrical resistivity structure of the mantle beneath the fast-spreading southern East Pacific Rise (EPR). The data reveal an asymmetric resistivity structure, with lower resistivity to the west of the ridge. The uppermost 100 kilometers of mantle immediately to the east of the ridge is consistent with a dry olivine resistivity structure indicating a mantle depleted of melt and volatiles. Mantle resistivities to the west of the ridge are consistent with a low-melt fraction (about 1 to 2 percent interconnected melt) distributed over a broad region and extending to depths of about 150 kilometers. The asymmetry in resistivity structure may be the result of asymmetric spreading rates and a westward migration of the ridge axis and suggests distinct styles of melt formation and delivery in the mantle beneath the two plates.

  American Association for the Advancement of Science (AAAS), Oct. 1999, Science, 286(5440) (5440), 752 - 756, English

  [Refereed]

  Scientific journal


• Constraints from magnetic anomalies on the structure of the Ulleung Basin, the East Sea (Japan Sea), using analytic signal and reduction to the pole transformations

  Park, C.H, N. Isezaki, N. Seama, S.L. Kim

  1999, Journal of the Geological Society of Korea, 35, 297 - 308

  [Refereed]

  Scientific journal


• Evolution of the Pacific-Antarctic Ridge South of the Udintsev Fracture Zone

  Louis Géli, Henri Bougault, Daniel Aslanian, Anne Briais, Laure Dosso, Joël Etoubleau, Jean-Pierre Le Formal, Marcia Maia, Hélène Ondréas, Jean-Louis Olivet, Chris Richardson, Keizo Sayanagi, Nobukazu Seama, Anjana Shah, Ivan Vlastelic, Michiko Yamamoto

  Because of the proximity of the Euler poles of rotation of the Pacific and Antarctic plates, small variations in plate kinematics are fully recorded in the axial morphology and in the geometry of the Pacific-Antarctic Ridge south of the Udintsev fracture zone. Swath bathymetry and magnetic data show that clockwise rotations of the relative motion between the Pacific and Antarctic plates over the last 6 million years resulted in rift propagation or in the linkage of ridge segments, with transitions from transform faults to giant overlapping spreading centers. This bimodal axial rearrangement has propagated southward for the last 30 to 35 million years, leaving trails on the sea floor along a 1000-kilometer-long V-shaped structure south of the Udintsev fracture zone.

  American Association for the Advancement of Science (AAAS), Nov. 1997, Science, 278(5341) (5341), 1281 - 1284, English

  [Refereed]

  Scientific journal


• Gravity anomalies of the Mid‐Atlantic Ridge north of the Kane Fracture Zone

  H. Fujimoto, N. Seama, J. Lin, T. Matsumoto, T. Tanaka, K. Fujioka

  High‐resolution gravity and multibeam bathymetric data were newly obtained from the Mid‐Atlantic Ridge (MAR) between latitudes 23°30′N and 28°N. Mantle Bouguer anomalies (MBA) show magmatic accretion focused at discrete centers along the spreading axis except near the oblique portion of the MAR between 24°30′–24°50′N. The MBA also indicates that crustal production near the TAG hydrothermal field has been relatively low during the last 2–3 My. The MBA show 120°‐striking off‐axis traces, indicating northward migration of the oblique portion and northward extension of the segments south of the oblique zone despite a long‐wavelength southward deepening of the axial topography. Observed gravity anomalies support a tectonic interpretation proposed from morphology and geomagnetic anomalies that the segment south of the oblique zone has extended northward by repeatedly adding short segments which migrated westward through asymmetric spreading in the oblique zone.

  American Geophysical Union (AGU), Nov. 1996, Geophysical Research Letters, 23(23) (23), 3431 - 3434, English

  [Refereed]

  Scientific journal


• Magnetic anomaly lineations and fracture zones deduced from vector magnetic anomalies in the West Enderby Basin

  Yoshifumi Nogi, Nobukazu Seama, Nobuhiro Isezaki, Yoichi Fukuda

  Vector geomagnetic anomaly field data obtained in the West Enderby Basin. Strikes of two-dimensional magnetic structures at the positions of their boundaries were determined using these data. The magnetic strikes were divided into two groups based on structural change and magnetic polarity change. A change in structural trend occurred around 500 km off the Antarctic coast to the east of Gunnerus Ridge. Approximately NNE-SSW structural trends dominate in the northern portion of the study area. In contrast, in the southern part, structural trends range between NW-SE and NNW-SSE directions. The latter trend is dominant just seaward of the continental slope of Antarctica, and is almost perpendicular to the coastline. ENE-WSW and E-W magnetic anomaly lineation trends, possibly belonging to the Mesozoic magnetic anomaly lineation sequence, are also observed in the southern part. Therefore, we surmise that the NW-SE and NNW-SSE-trending structures east of Gunnerus Ridge correspond to fracture zones formed during Mesozoic time and reflect the initial Gondwana break-up trend.

  1996, Geological Society Special Publication, 108, 265 - 273, English

  [Refereed]

  Scientific journal


• Morphological studies of the Ayu Trough, Philippine Sea – Caroline Plate Boundary

  T. Fujiwara, K. Tamaki, H. Fujimoto, T. Ishii, N. Seama, H. Toh, K. Koizumi, C. Igarashi, J. Segawa, K. Kobayashi, M. Kido, T. Seno, H. Kinoshita

  The Ayu Trough lies on the southern boundary between the Philippine Sea Plate and Caroline Plate. Although this trough may be the best place to study the evolution and kinematics of the Philippine Sea Plate, the origin and evolution of this trough are poorly understood. Our geophysical and morphological surveys in the northern part of the Ayu Trough revealed that the trough shares morphological similarities with slow‐spreading mid‐ocean ridges. The seafloor ages and an average spreading rate of the trough were inferred from the average length of the ridge segments, distribution of sediment thickness, and basement subsidence. Based on the seismic section at 3°30′N, the opening of the trough started about 25 Ma with an average half‐spreading rate 4.1 mm/yr. This spreading rate is much slower than some previous estimates. The present magma production rate and activity of the trough is estimated to be even lower than the 25 m.y. average. The seafloor depth of the trough axis and relief of the axial valley are approximately twice as deep as that of active mid‐ocean ridges. The trough axis valley is covered with sediment in contrast with the axial valleys of active mid‐ocean ridges. Sedimentation at the trough axis shows that the spreading rate has been quite slow for the last 2.5 Ma.

  American Geophysical Union (AGU), Jan. 1995, Geophysical Research Letters, 22(2) (2), 109 - 112

  [Refereed]

  Scientific journal


• One Year Observations with a Superconducting Gravimeter at Syowa Station, Antarctica

  Tadahiro Sato, Kazuo Shibuya, Yoshiaki Tamura, Masaki Kanao, Masatsugu Ooe, Kenta Okano, Yoichi Fukuda, Nobukazu Seama, Kazunari Nawa, Katsutada Kaminuma, Yoshiaki Ida, Mineo Kumazawa, Takeshi Yukutake

  Since March 22 of 1993, observations of Earth tides and Earth's free oscillations with a superconducting gravimeter (SCG) were continuing at Syowa Station, Antarctica (69.0°S, 39.5°E). Combined with the other SCG data from the global network, we expect to detect signals related with a fluid core resonance, core undertones in the fluid core, the Slichter mode of the inner core, etc. and to elucidate nature of long-period tides. Parallel observations were also continuing using a LaCoste & Romberg D gravimeter which was equipped with an electrostatic feedback amplifier and the same analog filter that were used in the SCG observations. Preliminary analyses of 1 year tidal data (March 22, 1993-March 21, 1994) generally support the previously obtained diurnal and semidiurnal tidal gravimetric factors, and confirm 10% larger M2 5 factor than the theoretical value by Dehant-Wahr. Subtraction of both short- and long-period tides from the original signals resulted in a fairly small (0.06 ugal/day: 1 μgal=10< SUP> -8< /SUP> m/s< SUP> 2< /SUP> ) trends including instrumental drift. An rms noise level of the data obtained through the MODE filter (MODE data) is estimated typically as 5-20 ugal (1 μgal=10< SUP> -11< /SUP> m/s< SUP> 2< /SUP> ). The recorded MODE data include high quality free oscillation signals from the Hokkaido-Nansei-Oki Earthquake (Ms =8.2) on July 12, and the earthquake of South of Mariana Island (Ms=8.2) on August 8, 1993. © 1995, The Geodetic Society of Japan. All rights reserved.

  1995, Journal of the Geodetic Society of Japan, 41(1) (1), 75 - 89, English

  [Refereed]

  Scientific journal


• A Subduction Angle of the Pacific Plate beneath the Japan Trench Inferred from Three Component Geomagnetic Anomalies.

  Asako Kitahara, Nobukazu Seama, Nobuhiro Isezaki

  Society of Geomagnetism and Earth, Planetary and Space Sciences, 1994, Journal of geomagnetism and geoelectricity, 46(6) (6), 455 - 462

  [Refereed]


• Resonance Parameters of the Free Core Nutation Measured from Three Superconducting Gravimeters in Japan.

  Tadahiro Sato, Yoshiaki Tamura, Toshihiro Higashi, Shuzo Takemoto, Ichiro Nakagawa, Noriyuki Morimoto, Yoichi Fukuda, Jiro Segawa, Nobukazu Seama

  Society of Geomagnetism and Earth, Planetary and Space Sciences, 1994, Journal of geomagnetism and geoelectricity, 46(7) (7), 571 - 586

  [Refereed]


• Superconducting Gravimeter Observations at Kakioka, Japan

  Nobukazu Seama, Yoichi Fukuda, Jiro Segawa

  Society of Geomagnetism and Earth, Planetary and Space Sciences, 1993, Journal of geomagnetism and geoelectricity, 45(11) (11), 1383 - 1394

  [Refereed]


• A new method for precise determination of the position and strike of magnetic boundaries using vector data of the geomagnetic anomaly field

  Seama, N, Nogi, Y, Isezaki, N

  1993, Geopys. J. Int., 113, 155-164

  [Refereed]


• Deep-tow survey in the KAIKO-Nankai cold seepage areas

  K. Kobayashi, J. Ashi, J. Boulegue, H. Cambray, N. Chamot-Rooke, H. Fujimoto, T. Furuta, J.T. Iiyama, T. Koizumi, K. Mitsuzawa, H. Monma, M. Murayama, J. Naka, M. Nakanishi, Y. Ogawa, K. Otsuka, M. Okada, A. Oshida, N. Shima, W. Soh, A. Takeuchi, M. Watanabe, T. Yamagata

  Elsevier BV, Apr. 1992, Earth and Planetary Science Letters, 109(3-4) (3-4), 347 - 354

  [Refereed]

  Scientific journal


• Studies of vector geomagnetic anomalies in the oceans (In Japanese with English abstract)

  Seama, N

  1992, Journal of Japan Society of Marine Survey Technology, 4(2) (2), 41 - 49

  [Refereed]


• The directions of magnetic anomaly lineations in Enderby Basin, off Antarctica

  Nogi, Y, Seama, N, Isezaki, N, Funaki M

  1992, Recent Progress in Antarctic Earth Sciences, TERRAPUB, 649-654

  [Refereed]


• Magnetic survey in Ongul islands

  Nogi, Y, Seama, N, Isezaki, N, Funaki M

  Total intensities of the geomagnetic field were measured in the eastern part of West Ongul Island and the southern part of East Ongul Island during the 30th Japanese Antarctic Research Expedition (JARE-30) in 1989. Measurements were carried out along two east-west observation lines in West Ongul Island and two east-west and three north-south observation lines in East Ongul Island. The variations of magnetic anomalies in West Ongul Island seem to correlate with the surface geology, while those in East Ongul Island do not. A model calculation showed a positive correlation of the obtained variations in West Ongul Island with the geological structure and the paleomagnetic results. However, widths and positions of the magnetic anomaly source model are slightly different from those of the surface geological structure. These differences provide information how the surface geological structure extends underground.

  National Institute of Polar Research, 1991, Proc. NIPR Symp. Antarct. Geosci., 5, 11 - 19, English

  [Refereed]


• Sea-floor magnetization in the eastern part of the Japan Basin and its tectonic implications

  Nobukazu Seama, Nobuhiro Isezaki

  Elsevier BV, Sep. 1990, Tectonophysics, 181(1-4) (1-4), 285 - 297

  [Refereed]

  Scientific journal


• Measurement of geomagnetic field at sea during JARE-30, 1988-1989

  Yoshifumi Nogi, Nobukazu Seama, Nobuhiro Isezaki, Minoru Funaki, Katsutada Kaminuma

  第30次南極地域観測において, 船上地磁気3成分磁力計による地磁気3成分測定およびプロトン磁力計による地磁気全磁力測定の同時観測を行った。プロトン磁力計の全磁力測定から船速の違いによるノイズの変化が見られた。このノイズの変化は, 船速が速くなりセンサーが不安定になることによって引き起こされたと考えられる。船上地磁気3成分測定からは, 船の船首方位の細かな揺動による短波長のノイズが見られた。船上地磁気3成分測定によって得られた地磁気3成分のデータに, プロトン磁力計によって得られた全磁力の結果をうまく適合することによって, 地磁気3成分のデータの絶対値に関してより信頼度の高いデータが得られた。現段階では, 地磁気3成分のデータの絶対値に関する問題を扱う場合プロトン磁力計との同時観測が必要である。以上の結果をもとに, 今後の海上における地磁気測定の改善が望まれる。Three components and total intensity of the geomagnetic field were measured by STCM (Shipboard Three Components Magnetometer) and a proton magentometer at the same time at sea during the 30th Japanese Antarctic Research Expedition. The measurements of total intensity of the geomagnetic field by a proton magnetometer showed a variation of noises in harmony with the variation of ship's velocity. This variation of noises may be caused by instability of the sensor due to large velocity of the ship. The measurements of three components of the geomagnetic field by STCM revealed short wavelength noiscs which were caused by small yawing of the ship. Reliable absolute values of three components of the geomagnetic field were obtained by adapting the total intensity of the geomagnetic field measured by a proton magnetometer to the data of three components of the geomagnetic field measured by STCM. In the present state of STCM, it is necessary to measure three components and total intensity of geomagnetic field by STCM and a proton magnetometer simultaneously, in case of obtaining the absolute values of three components of the geomagnetic field. These results suggest that improvement of measurement of the geomagnetic field at sea will be required.

  1990, Antarctic Record, 34(3) (3), 34, 346-356 - 356, Japanese

  [Refereed]


• Preliminary report of three components of geomagnetic field measured on board the icebreaker Shirase during JARE-30

  Nogi, Y, Seama, N, Isezaki, N

  Measurement of three components of geomagnetic field was carried out on board the icebreaker SHIRASE during the 30th Japanese Antarctic Research Expedition (JARE-30). Vector anomalies of geomagnetic field were obtained and the directions of magnetic lineations were determined from the vector anomalies. They are in good agreement with the results previously reported along the ship's tracks (e. g. ROYER et al. : Tectonophysics, 155,235,1988; ROYER and SANDWELL : J. Geophys. Res., 94,13755,1989), except for the Antarctic continental margin and the Enderby Basin. In the Antarctic continental margin, N-S trending magnetic structure that coincides with the Australian-Antarctic depression is detected between Australia and Antarctica and the local magnetic anomaly that seems to be caused by the Napier Complex appears between 50°E and 60°E along 63°S. Further, in the Enderby Basin around 60°S, N-S and NNE-SSW trending magnetic lineations which have never been reported before are detected. These results may suggest new constraints on the evolution of the Indian Ocean.

  National Institute of Polar Research, 1990, Proc. NIPR Symp. Antarct. Geosci., 4, 4, 191-200 - 200, English

  [Refereed]

• 海底を覆う鬼界カルデラ巨大噴火の噴出物

  清水 堅, 島 伸和

  Sep. 2024, 科学

  Introduction other


• Drilling on the submarine caldera wall of the Kikai Caldera

  羽生毅, 宮崎隆, TEJADA M.L.G., 島伸和, 金子克哉, 中岡礼奈, 清杉孝司, 鈴木桂子, 清水賢, 西来邦章, 佐藤勇輝

  2023, 日本火山学会講演予稿集, 2023 (Web)


• Imaging a 3-D resistivity structure under the Kikai submarine caldera volcano.

  小畑拓実, 荒木将允, 廣瀬時, 松野哲男, 南拓人, 大塚宏徳, 巽好幸, 杉岡裕子, 杉岡裕子, 市原寛, 島伸和, 島伸和

  2023, 地球電磁気・地球惑星圏学会総会及び講演会(Web), 154th


• The distribution of small faults and acoustic stratigraphy of the alluvium in the Osaka Bay, Japan, revealed by sub-bottom profiler data

  岩波知宏, 大塚宏徳, 松野哲男, 島伸和, 島伸和, 浜橋真理, 佐野守, 佐野守, 井和丸光, 井和丸光, 鈴木啓太, 鈴木啓太, 杉岡裕子, 杉岡裕子

  2023, 日本地質学会学術大会(Web), 130th


• 調査船による海底火山研究－鬼界海底カルデラプロジェクトを例として－

  島 伸和

  Mar. 2022, KANRIN（咸臨）, (101) (101), 22 - 27


• 現実的なマントル掘削のシナリオ

  島 伸和, 藤江 剛, 山下 幹也

  Mar. 2022, 号外地球, 72, 30 - 39


• Late Pleistocene to Holocene dynamic basin environment at the Osaka Bay: Stratigraphic expressions of tectonic deformation, sea level fluctuation, and tidal waves

  HAMAHASHI Mari, OTSUKA Hironori, SUZUKI Yoshiaki, ARIMOTO Jun, YAMAMOTO Yuzuru, YAMAMOTO Yuzuru, SEAMA Nobukazu, SEAMA Nobukazu, BOWDEN Stephen, BOWDEN Stephen, MATSUNO Tetsuo, SUGIOKA Hiroko, SUGIOKA Hiroko, SHIMIZU Satoshi, SHIMIZU Satoshi, IWAMARU Hikaru, IWAMARU Hikaru, SANO Mamoru, SANO Mamoru, SUZUKI Keita, SUZUKI Keita, KANEKO Katsuya, KANEKO Katsuya, NAKAHIGASHI Kazuo, TATSUMI Yoshiyuki

  2022, 日本地球惑星科学連合大会予稿集(Web), 2022


• Amphibious passive seismic observation at Kikai submarine caldera

  YAMAMOTO Yojiro, ITO Aki, ISHIHARA Yasushi, OBAYASHI Masayuki, TANAKA Satoru, NAKAMICHI Haruhisa, YAKIWARA Hiroshi, NAKATANI Yukihiro, SUGIOKA Hiroko, SUGIOKA Hiroko, OTSUKA Hironori, MATSUNO Tetsuo, SEAMA Nobukazu, SEAMA Nobukazu

  2022, 日本地球惑星科学連合大会予稿集(Web), 2022


• Preliminary results of ocean bottom pressure observation around Kikai submarine caldera, SW Japan

  ASAI Yuko, SEAMA Nobukazu, HANYU Tomoko, MATSUNO Tetsuo, HIROSE Hitoshi, MINAMI Takuto, SUGIOKA Hiroko

  2021, 日本地球惑星科学連合大会予稿集(Web), 2021


• Kikai Submarine Caldera Project - Investigations on Mechanism of Super-eruption

  Nobukazu Seama

  The Japan Institute of Marine Engineering, 01 Jan. 2021, Marine Engineering, 56(1) (1), 139 - 143, Japanese

  Introduction scientific journal


• An overview of volcanic rocks from submarine Kikai Caldera

  HANYU Takeshi, SEAMA Nobukazu, TANAKA Satoru, TATSUMI Yoshiyuki, ABE Shunsuke, HAMADA Morihisa, HANYU Tomoko, IWAMARU Hikaru, KADO Souko, KANEKO Katsuya, KIKUCHI Ryohei, KIYOSUGI Koji, MATSUNO Tetsuo, MCINTOSH Iona, MIYAZAKI Takashi, NAKAOKA Reina, OKAMOTO Nobuyuki, ORII Taiki, SHIMIZU Satoshi, SHINTANI Tsuyoshi, SUZUKI-KAMATA Keiko, TEJADA Maria Luisa, UEKI Kenta, VAGLAROV Bogdan Stefanov

  2020, 日本地球惑星科学連合大会予稿集(Web), 2020


• The MoHole: A Crustal Journey and Mantle Quest Workshop Report

  ILDEFONSE Benoît, ABE Natsue, BLACKMAN Donna K, CANALES J. Pablo, ISOZAKI Yoshio, KODAIRA Shuichi, MYERS Greg, NAKAMURA Kentaro, NEDIMOVIC Mladen, SKINNER Alesander, SEAMA Nobukazu, TAKAZAWA Eiichi, TEAGLE Damon A.H, TOMINAGA Masako, UMINO Susumu, WILSON Douglas S, YAMAO Masaoki

  Jun. 2010, Workshop Report, 1-67, English


• Oceanic Crustal Structure and Formation: IODP and ODP Achievements November 2002 - December 2005

  LARSEN Hans Christian, CANNAT Mathilde, CEULENEER Georges, FRüH-GREEN Gretchen, KODAIRA Shuichi, MACLEOD Chris, MILLER Jay, SEAMA Nobukazu, TATSUMI Yoshiyuki, TOOMEY Douglas

  Jun. 2009, Thematic Review, 2,1-65, English

  Introduction scientific journal


• Realistic Mohole using D/V Chikyu

  SEAMA Nobukazu, ABE Natsue, KODAIRA Shuichi

  2009, White paper for IODP New Ventures in Exploring Scientific Targets (INVEST), 1-5, English

  Others


• On Board Report of the recovery of OBEM (Ocean Bottom Electro - Magnetometer) during the 27th Umitaka-maru Cruise, 1/December/2008 - 2/January /2009

  SEAMA Nobukazu

  Jan. 2009, -, 1-11, English

  Others


• Campagne ESSRES – Tests magnétométriques – 19-26 juillet 2008

  DYMENT Jérôme, SAVARY Jean, CHOI Yujin, SEAMA Nobukazu

  Aug. 2008, Bref compte rendu, 1-5, English

  Others


• On Board Report of the Hakuho-maru Cruise KH-07-4 Leg 2

  SEAMA Nobukazu

  2008, -, 6-26/January /2008, 1-59, English

  Others


• On Board Cruise Report of KR07-16 Kairei Cruise

  SEAMA Nobukazu

  2007, -, 26/November-2/December/2007, 1, English

  Others


• On Board Cruise Report of KR06-12 Kairei Cruise

  Seama Nobukazu, T. Goto, K. Baba, R.L. Evans, A. White, T. Matsuno, R. Tsujino, A. Yoneda, G.Boren, J. Bailey, H. Moeller, A. Gardner, M. Aoki, M. Ido

  2006, 不明, 38741, English


• Magnetometric Resistivity 法の磁場の3次元フォワード計算(その2)―比抵抗異常領域がつくる磁場の特徴―

  多田 訓子, 木戸 元之, SEAMA NOBUKAZU

  2006, Conductivity Anomaly 研究会 2006 年論文集, 136 - 137, Japanese


• Surveys of the oceanic crust resistivity structure using a Magnetometric Resistivity method

  TADA N, SEAMA N

  2006, Butsuri-Tansa, 59(2), 171-180,, Japanese

  [Refereed]

  Introduction scientific journal


• 海底熱水系地下生物圏への地球物理学的アプローチ－地下生物圏の構造をどのように把握するか－

  島 伸和, 田中 明子

  実業公報社, 2004, 地質ニュース, 598 24-29(598) (598), 24 - 29, Japanese


• Preliminary report of KR02-14 Kairei cruise

  Seama, N, Goto, K, Nogi, Y, Ichiki, M, Kasaya, T, Tada, N, Iwamoto, H, Kitada, K, Matsuno, T, Yoshida, S, Kawada, Y, Ito, M, Ishii, R, Takizawa, K, Suyehiro, K, Utada, H, Shimoizumi, M

  2003, JAMSTEC Journal of Deep Sea Research, 22, 22, 89-106 - 106


• Developement of the Basic Processing System of Marine Geophysical Data (MAGBAT)

  Masao NAKANISHI, Chunghwa PARK, Keizou SAYANAGI, Kensaku TAMAKI, Yukari NAKASA, Atushi OSHIDA, Nobukazu SIMA

  Japan Society of Geoinformatics, 1987, Geological data processing, 1987(12) (12), 217 - 226

• 図説 地球科学の事典

  SEAMA NOBUKAZU

  Others, 朝倉書店, Apr. 2018, Japanese

  Scholarly book


• Back-arc spreading systems : geological, biological, chemical, and physical interactions

  Wiens, D.A., N. Seama and J. A. Conder

  Mantle structure and flow patterns beneath active back-arc basins inferred from passive seismic and electromagnetic methods, American Geophysical Union, 2006, English, ISBN: 9780875904313


• 「海洋調査フロンティア 海を計測する -増補版-」

  島 伸和

  第5章近年の海洋における地球物理観測技術の進歩 5.1コンプライアンス測定/5.2コントロールソースを用いた電気伝導度測定, 2004

• ⻤界カルデラ⽕⼭海域での地下⽐抵抗構造

  小畑 拓実, 松野 哲男, 南 拓人, 臼井 嘉哉, 市原 寛, 巽 好幸, 杉岡 裕子, 大塚 宏徳, 島 伸和

  SGEPSS CA研究会 2024年度研究集会, Mar. 2025

  Oral presentation


• KH-24-4 速報：インド洋トランスフォーム断層調査 MOWALL-CIR

  沖野 郷子, 町田 嗣樹, 森下 知晃, 道林 克禎, 石川 晃, 平野 直人, 李 毅兵, 藤井 昌和, 島 伸和, 峰岸 有紀, 矢萩 拓也, 砂村 倫成, 眞壁 明子, 乗船研究者一同

  海と地球のシンポジウム2024, Mar. 2025

  Oral presentation


• マリーセレストトランスフォーム断層を用いて海洋地殻の鉛直磁化構造を探る試み

  鈴木 諒翼, 島 伸和, 田村 千織, 芦田 将成, 小野 誠太郎, 沖野 郷子, 藤井 昌和

  海と地球のシンポジウム2024, Mar. 2025

  Oral presentation


• マリアナトラフの発達史

  小野 誠太郎, 沖野 郷子, 山崎 敏嗣, 島 伸和

  海と地球のシンポジウム2024, Mar. 2025

  Poster presentation


• 鬼界カルデラ海域における潮汐起囚の電磁場応答の研究

  柴田 悠, 野々山 達也, 島 伸和, 南 拓人, 小畑 拓実, 松野 哲男, 杉岡 裕子, 大塚 宏徳, 羽人 朋子, 山本 揚二朗, 中道 治久

  地球電磁気・地球惑星圏学会 2024年秋季年会, Nov. 2024

  Poster presentation


• グローバルトモグラフィーによる鬼界カルデラ周辺のP波速度構造

  大林 政行, 吉光 淳子, 山本 揚二朗, 伊藤 亜妃, 石原 靖, 田中 聡, 中道 治久, 八木原 寛, 仲谷 幸浩, 杉岡 裕子, 大塚 宏徳, 松野 哲男, 島 伸和

  日本火山学会2024年度秋季大会, Oct. 2024

  Poster presentation


• 地震波トモグラフィによる鬼界カルデラのマグマ供給系イメージング

  山本 揚二朗, 伊藤 亜妃, 石原 靖, 大林 政行, 田中聡, 中道 治久, 八木 原寛, 仲谷 幸浩, 杉岡 裕子, 大塚 宏徳, 松野 哲男, 島 伸和

  日本火山学会2024年度秋季大会, Oct. 2024

  Oral presentation


• Characteristics of the Kikai-Akahoya and Kikai-Tozurahara eruption deposits from submarine cores

  Nakaoka R., Suzuki K., Kaneko K., Seama N., Kiyosugi K., Yamamoto Y., Matsuno T., Hanyu T., Shimizu S., Tatsumi Y.

  PROGRAMME AND ABSTRACTS THE VOLCANOLOGICAL SOCIETY OF JAPAN, Oct. 2024, Japanese, The Volcanological Society of Japan

  Poster presentation


• 国際深海科学掘削計画：地震発生帯掘削の総括と新プログラム IODP3

  木下 正高, 島 伸和, 益田 晴恵, 江口 暢久, 斎藤 実篤

  2024年度日本地球化学会 第71回年会, Sep. 2024

  [Invited]

  Invited oral presentation


• Estimation of 3-D resistivity structure under the Kikai submarine caldera volcano

  Obata, T., Araki, M., Hirose, T., Matsuno, T., Minami, T., Usui, Y., Otsuka, H., Ichihara, H., Tatsumi, Y., Sugioka, H., Seama, N.

  The 26th Electromagnetic Induction Workshop, Sep. 2024

  Oral presentation


• Advancing the Magnetometric Resistivity Method:3D Forward Modeling with the Relaxation Technique

  Noriko Tada, Motoyuki Kido, Nobukazu Seama

  26th EM Induction Workshop, Sep. 2024


• Magmatic evolution leading to multiple calderagenic eruptions at Kikai volcano, Southwest Japan

  Maria Luisa Tejada, Tomoki Sato, Bogdan Vaglarov, Reina Nakaoka, Yoshi Tatsumi, Takeshi Hanyu, Qing Chang, Kenta Ueki, Katsuya Kaneko, Keiko Suzuki-Kamata, Takashi Miyazaki, Iona McIntosh, Nobukazu Seama, Koji Kiyosugi, Osamu Ishizuka, Morihisa Hamada

  Goldschmidt2024 abstracts, Aug. 2024, Geochemical Society


• 海陸自然地震観測による鬼界カルデラの地震波速度構造

  山本 揚二朗, 伊藤 亜妃, 石原 靖, 大林 政行, 田中 聡, 中道 治久, 八木原 寛, 仲谷 幸浩, 杉岡 裕子, 大塚 宏徳, 松野 哲男, 島 伸和

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• 7300年前の鬼界アカホヤ噴火以降の海底溶岩ドーム直下のマグマ供給系の進化（続編）

  浜田 盛久, 羽生 毅, マッキントシュ アイオナ, テハダ マリアルイザ, 常 青, 金子 克哉, 木村 純一, 清杉 孝司, 宮崎 隆, 中岡 礼奈, 西村 公宏, 佐藤 智紀, 島 伸和, 鈴木 桂子, 田中 聡, 巽 好幸, 上木 賢太, ヴァグラロフ ボグダン, 吉田 健太

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• Tracing the Kikai volcano evolution from geochemical surveys of subaerial and submarine deposits

  Maria Luisa Tejada, Takeshi Hanyu, Takashi Miyazaki, Morihisa Hamada, Qing Chang, Tomoki Sato, Iona McIntosh, Kenta Ueki, Bogdan Vaglarov, Nobukazu Seama, Katsuya Kaneko, Reina Nakaoka, Koji Kiyosugi, Keiko Suzuki-Kamata, Yoshi Tatsumi, Osamu Ishizuka

  日本地球惑星科学連合2024年大会, May 2024

  Poster presentation


• 地磁気異常データを用いたマリアナトラフの拡大過程

  小野 誠太郎, 沖野 郷子, 島 伸和

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• 最終氷期以降における大阪湾の音響層序と地殻変動

  岩波 知宏, 大塚 宏徳, 松野 哲男, 島 伸和, 浜橋 真理, 佐野 守, 井和丸 光, 鈴木 啓太, 杉岡 裕子

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• Magma re-injection after the 7.3 ka Kikai-Akahoya eruption of the Kikai submarine caldera volcano

  島 伸和, 長屋 暁大, 藤江 剛, 清水 賢, 中岡 礼奈, 田中 聡, 山本 揚二朗, 宮町 宏樹, 杉岡 裕子, 小平 秀一

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• 3-D resistivity structure under the Kikai submarine caldera volcano.

  小畑 拓実, 荒木 将允, 廣瀬 時, 松野 哲男, 南 拓人, 臼井 嘉哉, 大塚 宏徳, 市原 寛, 巽 好幸, 杉岡 裕子, 島 伸和

  日本地球惑星科学連合2024年大会, May 2024

  Oral presentation


• 3-D resistivity structure under the Kikai submarine caldera volcano

  Takumi Obata, Masamitsu Araki, Toki Hirose, Tetsuo Matsuno, Takuto Minami, Yoshiya Usui, Hironori Otsuka, Yoshiyuki Tatsumi, Hiroko Sugioka, Hiroshi Ichihara, Nobukazu Seama

  International Symposium “Submarine caldera volcanoes”, Mar. 2024, 神戸, International conference

  Oral presentation


• Seismic velocity structure at Kikai submarine caldera deduced from amphibious passive seismic observation

  Yojiro Yamamoto, Aki Ito, Yasushi Ishihara, Masayuki Obayashi, Satoru Tanaka, Haruhisa Nakamichi, Hiroshi Yakiwara, Yukihiro Nakatani, Hiroko Sugioka, Hironori Otsuka, Tet-suo Matsuno, Nobukazu Seama

  International Symposium “Submarine caldera volcanoes”, Mar. 2024, 神戸, International conference

  Oral presentation


• 7.3 ka Kikai-Akahoya eruption of the Kikai submarine caldera volcano and current sta-tus of magma re-injection

  Nobukazu Seama, Akihiro Nagaya, Gou Fujie, Satoshi Shimizu, Reina Nakaoka, Satoru Tanaka, Yojiro Yamamoto, Hiroki Miyamachi, Hiroko Sugioka, Shuichi Kodaira

  International Symposium “Submarine caldera volcanoes”, Mar. 2024, 神戸, International conference

  Oral presentation


• Magma sources and variability at Kikai Caldera, SW Japan pre-, syn- and post cal-deragenic eruptions

  M. L. G. Tejada, T. Hanyu, T. Miyazaki, M. Hamada, Q. Chang, T. Sato, I. McIntosh, K. Ueki, B. Vaglarov, N. Seama, K. Kaneko, R. Nakaoka, K. Kiyosugi, K. Suzuki-Kamata, O. Ishi-zuka

  International Symposium “Submarine caldera volcanoes”, Mar. 2024, 神戸, International conference

  Oral presentation


• Magma evolution from Tozurahara to Akahoya catastrophic eruptions at Kikai Caldera; a study on marine tephras from the Chikyu SCORE core

  Takeshi Hanyu, Nobukazu Seama, Katsuya Kaneko, Qing Chang, Reina Nakaoka, Koji Kiyosugi, Yuzuru Yamamoto, Tetsuo Matsuno, Keiko Suzuki-Kamata, Yoshiyuki Tatsumi

  International Symposium “Submarine caldera volcanoes”, Mar. 2024, 神戸, International conference

  Poster presentation


• 鬼界カルデラ火山海域での地下比抵抗構造

  小畑 拓実, 荒木 将允, 廣瀬 時, 松野 哲男, 南 拓人, 臼井 嘉哉, 大塚 宏徳, 巽 好幸, 杉岡 裕子, 市原 寛, 島 伸和

  海と地球のシンポジウム2023, Mar. 2024, 口頭, 東京, Domestic conference

  Oral presentation


• 北海道沖千島海溝での浅部微動分布に相関する構造

  山口 寛登, 小平 秀一, 藤江 剛, 野 徹雄, 中村 恭之, 白石 和也, 島 伸和

  日本地震学会2023秋季大会, Nov. 2023, 口頭, 横浜, Domestic conference

  Oral presentation


• 海陸自然地震観測による鬼界カルデラの地震波速度構造

  山本揚二朗, 伊藤亜妃, 石原 靖, 大林政行, 田中 聡, 中道治久, 八木原 寛, 仲谷幸浩, 杉岡裕子, 大塚宏徳, 松野哲男, 島 伸和

  日本火山学会2023年度秋季大会, Oct. 2023, Domestic conference

  Poster presentation


• 鬼界カルデラのマグマ源とその進化

  Maria Luisa Tejada, 羽生 毅, 宮崎 隆, 浜田盛久, 佐藤智紀, 島 伸和, 金子克哉, 中岡礼奈, 清杉孝司, 鈴木桂子, 石塚 治

  日本火山学会2023年度秋季大会, Oct. 2023, Domestic conference

  Poster presentation


• 鬼界カルデラの海底カルデラ壁における掘削

  羽生 毅, 宮崎 隆, Maria Luisa Tejada, 島 伸和, 金子克哉, 中岡礼奈, 清杉孝司, 鈴木桂子, 清水 賢, 西来邦章, 佐藤勇輝

  日本火山学会2023年度秋季大会, Oct. 2023, Domestic conference

  Oral presentation


• 鬼界カルデラ火山海底下の三次元比抵抗構造解析

  小畑 拓実, 荒木 将允, 廣瀬 時, 松野 哲男, 南 拓人, 大塚 宏徳, 巽 好幸, 杉岡 裕子, 市原 寛, 島 伸和

  地球電磁気・地球惑星圏学会2023年秋季年会, Sep. 2023, 口頭, 仙台, Domestic conference

  Oral presentation


• サブボトムプロファイラーデータによって明らかになった大阪湾における小断層の分布と沖積層の音響層序区分

  岩波 知宏, 大塚 宏徳, 松野 哲男, 島 伸和, 浜橋 真理, 佐野 守, 井和丸 光, 鈴木 啓太, 杉岡 裕子

  日本地質学会第130年学術大会, Sep. 2023, 口頭, 京都, Domestic conference

  Oral presentation


• Shallow fault-related folding and late Quaternary slip rate of the Osaka Bay Fault, western Japan

  Mari Hamahashi, Hironori Otsuka, Yoshiaki Suzuki, Jun Arimoto, Tetsuo Matsuno, Nobukazu Seama, Yuzuru Yamamoto, Hiroko Sugioka, Stephen A. Bowden, Satoshi Shimizu, Hikaru Iwamaru, Mamoru Sano, Keita Suzuki, Katsuya Kaneko, Kazuo Nakahigashi, Yoshiyuki Tatsumi

  International Joint Workshop on Slow-to-Fast Earthquakes 2023, Sep. 2023, Poster, 東京・オンライン, International conference

  Poster presentation


• 鬼界海底カルデラ火山の集中的な調査研究

  島 伸和

  日本地球惑星科学連合2023年大会, May 2023, 口頭, 千葉・オンライン, Domestic conference

  [Invited]

  Invited oral presentation


• 7300年前の鬼界アカホヤ噴火以降の海底溶岩ドーム直下マグマ供給系の進化

  浜田 盛久, 羽生 毅, マッキントシュ アイオナ, テハダ マリアルイザ, チャン チン, 金子 克哉, 木村 純一, 清杉 孝司, 宮崎 隆, 中岡 礼奈, 西村 公宏, 佐藤 智紀, 島 伸和, 鈴木 桂子, 田中 聡, 巽 好幸, 上木 賢太

  日本地球惑星科学連合2023年大会, May 2023, 口頭, 千葉・オンライン, Domestic conference

  Oral presentation


• 屈折法地震探査によって明らかになった鬼界カルデラ海底火山地下の低速度異常

  長屋 暁大, 藤江 剛, 小平 秀一, 田中 聡, 山本 揚二朗, 杉岡 裕子, 宮町 宏樹, 松野 哲男, 大塚 宏徳, 鈴木 啓太, 島 伸和

  日本地球惑星科学連合2023年大会, May 2023, 口頭, 千葉・オンライン, Domestic conference

  Oral presentation


• Resistivity structure of the Lau basin as inferred from M2 tidal magnetic variation at the seafloor

  南 拓人, 中家 徳真, 島 伸和

  日本地球惑星科学連合2023年大会, May 2023, 口頭, 千葉・オンライン, Domestic conference

  Oral presentation


• Investigating the formation of the Kikai submarine lava dome using matrix glass volatile contents

  Iona McIntosh, Morihisa Hamada, Takeshi Hanyu, Maria Luisa Tejada, Takashi Miyazaki, Qing Chang, Bogdan Vaglarov, Katsuya Kaneko, Koji Kiyosugi, Reina Nakaoka, Keiko Suzuki-Kamata, Nobukazu Seama

  Japan Geoscience Union Meeting 2023, May 2023, Poster, 千葉・オンライン, Domestic conference

  Poster presentation


• Imaging 3D resistivity structure under the seafloor of Kikai caldera volcano

  小畑 拓実, 荒木 将允, 廣瀬 時, 松野 哲男, 南 拓人, 大塚 宏徳, 巽 好幸, 杉岡 裕子, 羽生 毅, 田中 聡, 市原 寛, 島 伸和

  日本地球惑星科学連合2023年大会, May 2023, 口頭, 千葉・オンライン, Domestic conference

  Oral presentation


• 鬼界海底カルデラの総合調査

  田中 聡, 羽生 毅, 藤江 剛, 山本 揚二朗, 小平 秀一, 宮崎 隆, 臼井 洋一, 上木 賢太, Maria Luisa G. Tejada, 宮町 宏樹, 西来 邦明, 佐藤 勇輝, 島 伸和, 鈴木 桂子, 金子 克哉, 松野 哲男, 清杉 孝司, 中岡 礼奈, 大塚 宏徳, 清水 賢, 荒木 将允, 長屋 暁大, 小畑 拓実, ならびに課題提案者一同

  海と地球のシンポジウム2022, Mar. 2023, Japanese, 東京, Domestic conference

  Oral presentation


• 屈折法地震波構造探査によって明らかになった鬼界カルデラ火山直下の低速度領域

  長屋 暁大, 藤江 剛, 小平 秀一, 田中 聡, 山本 揚二朗, 杉岡 裕子、宮町 宏樹、松野 哲男, 大塚 宏徳, 鈴木 啓太, 島 伸和

  海と地球のシンポジウム2022, Mar. 2023, Japanese, 東京, Domestic conference

  Oral presentation


• 鬼界カルデラ火山海底下の三次元比抵抗構造解析

  小畑 拓実, 荒木 将允, 廣瀬 時, 沖園 雄希, 松野 哲男, 南 拓人, 大塚 宏徳, 巽 好幸, 杉岡 裕子, 島 伸和,羽生 毅, 田中 聡, 市原 寛

  海と地球のシンポジウム2022, Mar. 2023, Japanese, 東京, Domestic conference

  Oral presentation


• 鬼界カルデラ破局噴火のマグマ準備過程

  羽生 毅, 常 青,中岡 礼奈, 清杉 孝司, 金子 克哉, 鈴木 桂子, 山本 由弦, 松野 哲男, 島 伸和, 巽 好幸

  海と地球のシンポジウム2022, Mar. 2023, Japanese, 東京, Domestic conference

  Oral presentation


• ラウ海盆における潮汐起因磁場の3D順計算

  中家 徳真, 南 拓人, 島 伸和

  地球電磁気・地球惑星圏学会2022年秋学会, Nov. 2022


• 海底地形効果を考慮した3次元比抵抗構造解析手法の開発

  小畑 拓実, 荒木 将允, 松野 哲男, 南 拓人, 島 伸和

  地球電磁気・地球惑星圏学会2022年秋学会, Nov. 2022, Japanese, 神奈川, Domestic conference

  Oral presentation


• 北海道沖千島海溝沈み込み帯における海底谷を挟んだ構造差とプレート間すべりの関係

  山口 寛登, 小平 秀一, 藤江 剛, 野 徹雄, 中村 恭之, 白石 和也, 島 伸和

  日本地震学会2022年度秋季大会, Oct. 2022, Japanese, 札幌, Domestic conference

  Oral presentation


• 屈折法地震波探査による鬼界カルデラ地下の地震波速度構造の推定

  長屋 暁大, 藤江 剛, 小平 秀一, 田中 聡, 山本 揚二朗, 杉岡 裕子, 宮町 宏樹, 松野 哲男, 大塚 宏徳, 鈴木 啓太, 島 伸和

  日本地震学会2022年度秋季大会, Oct. 2022, Japanese, 札幌, Domestic conference

  Oral presentation


• 屈折法地震波探査によって推定された鬼界カルデラ地下の地震波速度構造

  長屋 暁大, 藤江 剛, 小平 秀一, 田中 聡, 山本 揚二朗, 杉岡 裕子, 宮町 宏樹, 松野 哲男, 大塚 宏徳, 鈴木 啓太, 島 伸和

  日本火山学会2022年度秋季大会, Oct. 2022, Japanese, 静岡・オンライン, Domestic conference

  Oral presentation


• 海底掘削試料から明らかになった鬼界カルデラ火山噴出物の特徴

  中岡 礼奈、金子 克哉、島 伸和、鈴木 桂子、清杉 孝司、羽生 毅、山本 由弦、松野 哲男、清水 賢、杉岡 裕子、巽 好幸

  2022年度 日本地球化学会 第69回年会, Sep. 2022, Japanese, 高知・オンライン, Domestic conference

  [Invited]

  Oral presentation


• 鬼界カルデラ破局噴火の噴火準備過程―ちきゅうSCORE試料よりー

  羽生 毅, 常 青, 金子 克哉, 中岡 礼奈, 清杉 孝司, 鈴木 桂子, 山本 由弦, 松野 哲男, 島 伸和, 巽 好幸

  2022年度 日本地球化学会 第69回年会, Sep. 2022, Japanese, 高知・オンライン, Domestic conference

  Oral presentation


• 鬼界海底カルデラにおける海陸自然地震観測

  山本 揚二朗, 伊藤 亜妃, 石原 靖, 大林 政行, 田中 聡, 中道 治久, 八木原 寛, 仲谷 幸浩, 、杉岡 裕子, 大塚 宏徳, 松野 哲男, 島 伸和

  日本地球惑星科学連合2022年大会, Jun. 2022, Japanese, 千葉・オンライン, Domestic conference

  Poster presentation


• Investigation of subaerial and submarine deposits of pyroclastic density currents: A case study at Kikai volcano, SW Japan

  清杉 孝司, 出口 翔太, 金子 克哉, 鈴木 桂子, 中岡 礼奈, 清水 賢, 島 伸和, 巽 好幸, 羽生 毅

  日本地球惑星科学連合2022年大会, May 2022, Japanese, 千葉・オンライン, Domestic conference

  Oral presentation


• 反射法地震探査データによる北海道沖千島海溝前弧の地下構造

  山口 寛登, 小平 秀一, 藤江 剛, 島 伸和

  日本地球惑星科学連合2022年大会, May 2022, Japanese, 千葉・オンライン, Domestic conference

  Oral presentation


• Investigating the formation of the Kikai submarine lava dome using matrix glass volatile contents

  Iona McIntosh, Morihisa Hamada, Takeshi Hanyu, Maria Luisa Tejada, Takashi Miyazaki, Qing Chang, Bogdan Vaglarov, Katsuya Kaneko, Koji Kiyosugi, Reina Nakaoka, Keiko Suzuki-Kamata, Nobukazu Seama

  Japan Geoscience Union Meeting 2022, May 2022, Japanese, Chiba / Online, Domestic conference

  Oral presentation


• Late Pleistocene to Holocene dynamic basin environment at the Osaka Bay: Stratigraphic expressions of tectonic deformation, sea level fluctuation, and tidal waves

  浜橋 真理, 大塚 宏徳, 鈴木 克明, 有元 純, 山本 由弦, 島 伸和, Bowden Stephen, 松野 哲男, 杉岡 裕子, 清水 賢, 井和丸 光, 佐野 守, 鈴木 啓太, 金子 克哉, 中東 和夫, 巽 好幸

  日本地球惑星科学連合2022年大会, May 2022, Japanese, 千葉・オンライン, Domestic conference

  Oral presentation


• フラクチャーゾーンとその周辺における海洋性地殻の形成と変遷

  近都麻衣, 島伸和, 藤井昌和, 羽入朋子

  InterRidge-Japan研究集会, Nov. 2021


• フラクチャーゾーンとその周辺における海洋性地殻の形成と変遷

  近都麻衣, 島伸和, 藤井昌和, 羽入朋子

  SGEPSS 第 149 回総会・講演会, Nov. 2021


• 鬼界アカホヤ噴火噴出物の陸上及び海底堆積物の対比

  中岡 礼奈, 鈴木 桂子, 清水 賢, 金子 克哉, 島 伸和, 清杉 孝司, 羽生 毅, 巽 好幸, CK20-S01 Leg2 乗船研究者一同, KS19-17 乗船研究者一同, KR20-11 乗船研究者一同

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• Shallow structure and late Quaternary slip rate on the Osaka Bay Fault: Aspects of climate-tectonic interaction

  浜橋 真理, 大塚 宏徳, 鈴木 克明, 有元 純, 松野 哲男, 島 伸和, 清水 賢, 井和丸 光, 佐野 守, 鈴木 啓太, 金子 克哉, 中東 和夫, 日高 伊都子, 山本 由弦, 巽 好幸

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• 薩摩半島南方における海底地すべりを起因とする堆積構造

  山口 寛登, 佐野 守, 清水 賢, 井和丸 光, 島 伸和, 山本 由弦, 大塚 宏徳, 松野 哲男, 巽 好幸

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• 鬼界カルデラ・アカホヤ噴火による水中火砕堆積物の堆積様式

  清水 賢, 島 伸和, 中岡 礼奈, 鈴木 桂子, 清杉 孝司, 金子 克哉, 松野 哲男, 巽 好幸

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• Drilling of Kikai caldera volcano for elucidation of magma plumbing system and flow-deposition processes of large ignimbrite

  金子 克哉, 羽生 毅, 中岡 礼奈, 清杉 孝司, 島 伸和, 松野 哲男, 山本 揚二朗, 羽入 朋子

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン

  [Invited]


• 重力異常から推定される鬼界カルデラ周辺の地殻構造

  羽入 朋子, 清水 賢, 山口 寛登, 森田 結子, 島 伸和

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• 鬼界海底カルデラ付近で得られた海底圧力観測の初期的な結果

  浅井 ゆう子, 島 伸和, 羽入 朋子, 松野 哲男, 廣瀬 仁, 南 拓人, 杉岡 裕子

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• ラウ海盆における潮汐起因磁場変動の一次元順計算：計算結果と海底磁場データ の比較および比抵抗構造に対する感度について

  中家 徳真, 南 拓人, 島 伸和

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• 地形効果を含む海底MTデータを扱う3次元インバージョンコードの開発 ～フォワード問題に関して～

  荒木 将允, 松野 哲男, 島 伸和, 南 拓人

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• Magnetic and gravity constraints on crustal structure of the Nosappu Fracture Zone, Northwestern Pacific

  近都 麻衣, 島 伸和, 藤井 昌和, 羽入 朋子

  日本地球惑星科学連合2021年大会, Jun. 2021, オンライン


• 鬼界海底カルデラ火山における地球物理学的観測及び地質岩石学的調査

  羽生毅, 田中聡, 伊藤亜妃, 山本揚二朗, 宮崎隆, 浜田盛久, MariaLuisaG. Tejada, 上木賢太, Bogdan S. Vaglarov, Iona McIntosh, 小平秀一, 末次大輔, 田村芳彦, 藤江剛, 堀高峰, 三浦誠一, 多田訓子, 原口悟, 中島倫也, 中岡礼奈, 杉岡裕子, 松野哲男, 清杉孝司, 大塚宏徳, 鈴木桂子, 岡本信行, 金子克哉, 菊池瞭平, 角想子, 織井大樹, 荒木将允, 島伸和, 巽好幸, 浜野洋三

  海と地球のシンポジウム2020, Dec. 2020

  Oral presentation


• 鬼界海底巨大カルデラ火山における二重カルデラ形成過程の解明―新青丸 KS-19-17 航海概要報告―

  島伸和, 清杉孝司, 中岡礼奈, 松野哲男, 金子克哉, 清水賢, 鈴木桂子, 岡本信行, 羽入朋子, 井和丸光, 阿部俊輔, 佐野守, 木村純一, 杉岡裕子, 巽好幸, 羽生毅, 新谷毅, 益田晴恵, 亀尾桂, 沖野郷子, 榎正憲, 石塚治

  海と地球のシンポジウム2020, Dec. 2020

  Oral presentation


• An overview of volcanic rocks from submarine Kikai Caldera

  Takeshi Hanyu, Nobukazu Seama, Satoru Tanaka, Yoshiyuki Tatsumi, Shunsuke Abe, Morihisa Hamada, Tomoko Hanyu, Hikaru Iwamaru, Souko Kado, Katsuya Kaneko, Ryohei Kikuchi, Koji Kiyosugi, Tetsuo Matsuno, Iona McIntosh, Takashi Miyazaki, Reina NAKAOKA, Nobuyuki Okamoto, Taiki Orii, Satoshi Shimizu, Tsuyoshi Shintani, Keiko Suzuki-Kamata,Maria Luisa Tejada, Kenta Ueki, Bogdan Stefanov Vaglarov

  JpGU-AGU joint Meeting 2020, May 2020, English

  Oral presentation


• Preliminary report of marine sediments drilled and cored by D/V Chikyu at Kikai volcano, SW Japan

  Koji Kiyosugi, Yoshiyuki Tatsumi, Keiko Suzuki-Kamata, Katsuya Kaneko, Reina NAKAOKA,Yuzuru Yamamoto, Takeshi Hanyu, Satoshi Shimizu, Nobukazu Seama, Tetsuo Matsuno,Ryohei Kikuchi, Hiroto Yamaguchi

  JpGU-AGU joint Meeting 2020, May 2020, English

  Oral presentation


• Seismic facies and distribution of submarine pyroclastic depositsoriginated from multiple large-scale eruptions of Kikai caldera

  清水賢, 中岡礼奈, 島伸和, 羽入朋子, 鈴木桂子, 清杉孝司, 金子克哉, 松野哲男, 井和丸光, 羽生毅, 阿部俊輔, 岡本信行, 巽好幸

  JpGU-AGU joint Meeting 2020, May 2020, Japanese

  Oral presentation


• Pre-prososal 951: The middle aged upper crust penetration on theNorth Arch off-Hawaii MoHole candidate site

  Susumu Umino, Tomoaki Morishita, Jun-Ichi Kimura, Mikiya Yamashita, NobukazuSeama, Shigeaki Ono, Natsue Abe, Katsuyoshi Michibayashi

  JpGU-AGU joint Meeting 2020, May 2020, English

  Oral presentation


• Short to long term morphological changes and migration of sandwaves in a semi-enclosed sea: a case study in Okinose area of OsakaBay

  Kojima Hibiki1, Atsushi Tani, Tetsuo Matsuno, Mamoru Sano, Nobukazu Seama, NoritakaEndo, Ken'ichi Ohkushi, Xu Zhang, Yusuke Uchiyama

  JpGU-AGU joint Meeting 2020, May 2020, English

  Oral presentation


• Structure of submarine mass-transport complexes(MTCs) southernMt.Kaimon

  山口寛登, 佐野守, 清水賢, 井和丸光, 島伸和, 松野哲男, 巽好幸

  JpGU-AGU joint Meeting 2020, May 2020, Japanese

  Oral presentation


• Distribution of the volcanic rock around Kikai caldera submarine volcano, estimated from the geomagnetic anomalies

  Tomoko Hanyu, Mamoru Sano, Hiroto Yamaguchi, Satoshi Shimizu, Tetsuo Matsuno, Masakazu Fujii, Yoshifumi Nogi, Nobukazu Seama

  JpGU-AGU joint Meeting 2020, May 2020, English

  Oral presentation


• How fracture zones work on subducting lithosphere?

  Nobukazu Seama, Tomoeki Nakakuki

  JpGU-AGU joint Meeting 2020, May 2020, English

  Poster presentation


• Flow and depositional processes of the Koya Pyroclastic Flow formed by the Kikai caldera-forming eruption at 7.3 ka

  Reina Nakaoka, Keiko Suzuki-Kamata, Satoshi Shimizu, Nobukazu Seama, Katsuya Kaneko, Koji Kiyosugi, Tetsuo Matsuno, Yoshiyuki Tatsumi

  American Geophysical Union(AGU) Fall Meeting 2019, Dec. 2019, San Francisco, International conference

  Oral presentation


• Geomagnetic paleointensity variation during the Cretaceous Normal Superchron

  Nobukazu Seama, Jerome Dyment, Taichi Sato, Yves Gallet, Kyoko Okino, Roi Granot, Yoshifumi Nogi, Nobutatsu Mochizuki, Toshitsugu Yamazaki

  InterRidge-Japan研究集会：海洋地殻－マントルの新たな実像：オマーン掘削から、海域観測から, Nov. 2019, 東京大学大気海洋研究所, Domestic conference

  Poster presentation


• The structure of Submarine landslide at Mt. Kaimon offshore

  Yamaguchi Hiroto, Sano Mamoru, Shimizu Satoshi, Iwamaru Hikaru, Seama Nobukazu, Matsuno Tetsuo, Tatsumi Yoshiyuki

  InterRidge-Japan研究集会：海洋地殻－マントルの新たな実像：オマーン掘削から、海域観測から, Nov. 2019, 東京大学大気海洋研究所, Domestic conference

  Poster presentation


• Magnetic anomalies around Kikai caldera submarine volcano

  Tomoko HANYU, Mamoru SANO,Tetsuo MATSUNO, Masakazu FUJII, Yoshifumi NOGI, Nobukazu SEAMA

  InterRidge-Japan研究集会：海洋地殻－マントルの新たな実像：オマーン掘削から、海域観測から, Nov. 2019, 東京大学大気海洋研究所, Domestic conference

  Oral presentation


• Governing factors of the mode of plate spreading that determine the oceanic crust architecture －the middle-aged upper crust drilling project Off-Hawaii－

  UMINO, S., Morishita, T., Kimura, J., Ono, S., Abe, N., Yamashita, M., Garcia, M., Klein, F., Tominaga, M., Seama, N., Michibayashi, K.

  InterRidge-Japan研究集会：海洋地殻－マントルの新たな実像：オマーン掘削から、海域観測から, Nov. 2019, 東京大学大気海洋研究所, Domestic conference

  Oral presentation


• Integrated study on submarine super-eruption, Kikai caldera

  Nobukazu Seama

  InterRidge-Japan研究集会：海洋地殻－マントルの新たな実像：オマーン掘削から、海域観測から, Nov. 2019, 東京大学大気海洋研究所, Domestic conference

  Oral presentation


• Basin scale water circulation inferred from geophysical evidences and numerical modelling

  Nobukazu Seama

  InterRidge Theoretical Institute 2019 ‘Hydrothermalism in 4D', Nov. 2019, Banyuls-sur-mer, France, International conference

  [Invited]

  Keynote oral presentation


• 幸屋火砕流の発生・流動様式

  鈴木 桂子, 中岡 礼奈, 清杉 孝司, 清水 賢, 井和丸 光, 松野 哲男, 島 伸和, 巽 好幸

  日本火山学会2019年度秋季大会, Sep. 2019, 神戸大学, Domestic conference

  Oral presentation


• 海洋地殻構造が示すプレート拡大モードの解明 -ハワイ沖モホール候補地における上部海 洋地殻貫通計画

  海野 進, 森下 知晃, 木村 純一, 山下 幹也, ガルシア マイケル, クライン フリーダー, 島 伸和, 小野 重明, 阿部 なつ江, 道林 克禎, 富永 雅子

  日本鉱物科学会2019年年会, Sep. 2019, 九州大学 伊都キャンパス, Domestic conference

  Oral presentation


• Asymmetric seafloor spreading in back-arc basins: Evidences from the Southern Mariana back-arc basin

  Nobukazu Seama

  International Workshop on Western Pacific Marginal Sea Geodynamics, Jul. 2019, English, Tongji University, Shanghai, China, International conference

  [Invited]

  Invited oral presentation


• Migration of sand waves observed in Okinose area of Osaka Bay

  Kojima Hibiki, Tetsuo Matsuno, Mamoru Sano, Nobukazu Seama, Noritaka Endo, Ken'ichi Ohkushi, Atsushi Tani

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• An investigation of three-dimensional electrical resistivity structure under Kikai Caldera

  Tetsuo Matsuno, Toki Hirose, Yuuki Okizono, Nobukazu Seama, Hiroshi Ichihara, Hiroko Sugioka, Yoshiyuki Tatsumi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• 鬼界カルデラ・アカホヤ噴火の水中火砕流の分布

  Satoshi Shimizu, Nobukazu Seama, Reina Nakaoka, Tetsuo Matsuno, Koji Kiyosugi, Hikaru Iwamaru, Mamoru Sano, Kimihiro Nishimura, Keiko Suzuki-Kamata, Katsuya Kaneko, Hiroto Yamaguchi, Misaki Horiuchi, Toki Hirose, Kazuki Hayashi, Yoshiyuki Tatsumi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• The Analysis of magnetotelluric sounding data on Kikai submarine caldera

  Toki Hirose, Tetsuo Matsuno, Nobukazu Seama, Yuki Okizono, Hiroshi Ichihara, Hiroko Sugioka, Yoshiyuki Tatsumi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• Investigating Origin of landslide-like bathymetric feature at southernMt.Kaimon using bathymetric and multichannel seismic reflectionsurveys

  Hiroto Yamaguchi, Satoshi Shimizu, Hikaru Iwamaru, Mamoru Sano, Nobukazu Seama, Misaki Horiuchi, Tetsuo Matsuno, Yoshiyuki Tatsumi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Poster presentation


• Identification of submarine volcanic ash around the Kikai caldera with the Koya pyroclastic flow deposit inferred from glass composition

  Reina Nakaoka, Keiko Suzuki-Kamata, Satoshi Shimizu, Yoshiyuki Tatsumi, Katsuya Kaneko, Koji Kiyosugi, Nobukazu Seama, Tetsuo Matsuno, Kimihiro Nishimura, Kazuki Hayashi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• Summary of Kikai submarine caldera researches conducted by KOBEC(Kobe Ocean-Bottom Exploration Center)

  Nobukazu Seama, Tetsuo Matsuno, Koji Kiyosug, Satoshi Shimizu, Reina Nakaoka, Keiko Suzuki-Kamata, Yasutomo Seto, Mamoru Sano, Yuiko Morita, Hikaru Iwamaru, Haruhisa Morozumi, Misaki Horiuchi, Kimihiro Nishimura, Hiroshi Ichihara, Kazuki Hayashi, Toki Hirose, Katsuya Kaneko, Hiroto Yamaguchi, Yuki Okizono, Hiroko Sugioka, Kazuo Nakahigashi, Yojiro Yamamoto, Tatsuya Koda, Shuichi Kodaira, Yoshiyuki Tatsumi, Scientific Party of T, S Fukae-maru, Kikai caldera, research cruises

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• The Cretaceous Normal Superchron: records from the Pacific, Indian and Atlantic oceanic crust

  Nobukazu Seama, Jerome Dyment, Taichi Sato, Yves Gallet, Kyoko Okino, Roi Granot, Yoshifumi Nogi, Nobutatsu Mochizuki, Toshitsugu Yamazaki

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• Preliminary report of the sea floor survey by a remotely operatedvehicle (ROV) at the Kikai caldera, SW Japan

  Koji Kiyosugi, Keiko Suzuki-Kamata, Haruhisa Morozumi, Yoshiyuki Tatsumi, Katsuya Kaneko, Reina Nakaoka, Mamoru Sano, Satoshi Shimizu, Hikaru Iwamaru, Nobukazu Seama, Tetsuo Matsuno, Kimihiro Nishimura, Kazuki Hayashi, Misaki Horiuchi

  Japan Geoscience Union Meeting 2019, May 2019, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• 南部マリアナ背弧拡大海嶺下の上部マントル比抵抗構造の解明

  MATSUNO TETSUO, SEAMA NOBUKAZU, SHINDO HARUKA, NOGI YOSHIFUMI, OKINO KYOKO

  地球電磁気・地球惑星圏学会 第144回総会及び講演会, Nov. 2018, Japanese, Domestic conference

  Poster presentation


• 背弧海盆の非対称拡大を説明する仮説：南マリアナトラフでの観測事実と数値シミュレーション

  島 伸和, 中久喜 伴益, 松野 哲男, 沖野 郷子

  日本地球惑星科学連合2018年大会, May 2018, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• The characteristics of seismic stratigraphic facies of Kikai submarine caldera and off the southern Kyusyu

  Satoshi Shimizu, Hikaru Iwamaru, Nobukazu Seama, Tetsuo Matsuno, Hiroshi Ichihara, Mamoru Sano, Hiroko Sugioka, Kazuo Nakahigashi, Yojiro Yamamoto, Kimihiro Nishimura, Yuka Furukawa, Misaki Horiuchi, Toki Hirose, Yasutomo Seto, Yoshiyuki Tatsumi

  Japan Geoscience Union Meeting 2018, May 2018, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• The significance of the surface excavation in the Kikai caldera, southern Kyushu

  Keiko Suzuki-Kamata, Yoshiyuki Tatsusmi, Kouji Kiyosugi, Reina Nakaoka, Nobukazu Seama, Tetsuo Matsuno, Satoshi Shimizu, Mamoru Sano, Hikaru Iwamaru

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Oral presentation


• Seafloor electromagnetic investigations of the upper mantle of the Mariana back-arc spreading and subduction system

  Tetsuo Matsuno, Nobukazu Seama

  Japan Geoscience Union Meeting 2018, May 2018, English, Makuhari Messe, Chiba, International conference

  Poster presentation


• Integrated marine investigations of Kikai Caldera, SW Japan

  Tetsuo Matsuno, Yoshiyuki Tatsumi, Nobukazu Seama, Keiko Suzuki-Kamata, Hiroshi Ichihara, Koji Kiyosugi, Reina Nakaoka, Satoshi Shimizu, Mamoru Sano, Hikaru Iwamaru, Haruhisa Morozumi, Hiroko Sugioka, Kazuo Nakahigashi, Yojiro Yamamoto, Kazuki Hayashi, Kimihiro Nishimura, Yuka Furukawa, Misaki Horiuchi, Daichi Nakata, Ryoto Nakamura, Hirose Toki, Yasutomo Seto, Atsuhiro Oshige, Hideaki Takizawa, Tatsuro Chiba, Shuichi Kodaira

  Japan Geoscience Union Meeting 2018, May 2018, Japanese, Makuhari Messe, Chiba, Domestic conference

  Oral presentation


• 背弧海盆の非対称拡大とその要因:南マリアナトラフでの観測事実と数値シミュ レーション

  SEAMA NOBUKAZU

  太平洋アレイ, Feb. 2018, Japanese, 東京大学地震研究所, Domestic conference

  Oral presentation


• Enhanced and asymmetric melting beneath the southern Mariana back-arc spreading ridge under the influence of the Pacific plate subduction

  Matsuno Tetsuo, SeamaNobukazu, Shindo Haruka, Nogi Yoshifumi, Okino Kyoko

  American Geophysical Union 2017 Fall Meeting, Dec. 2017, English, New Orleans, USA, International conference

  Poster presentation


• 背弧海盆の非対称拡大はどのようにして起こるのか？-南マリアナトラフでの観測事実と数値シミュレーション-

  SEAMA NOBUKAZU, 中久喜 伴益, MATSUNO TETSUO, 沖野 郷子

  InterRidge-Japan研究集会, Nov. 2017, Japanese, 東京大学大気海洋研究所, Domestic conference

  Oral presentation


• トランスフォーム断層における地磁気異常の要因の推定

  古川 優和, 藤井 昌和, SEAMA NOBUKAZU, 沖野 郷子

  InterRidge-Japan研究集会, Nov. 2017, Japanese, 東京大学大気海洋研究所, Domestic conference

  Poster presentation


• 伊豆・小笠原・マリアナ弧の背弧海盆で見られる2種類の上部海洋地殻地震波速度構造

  古川 優和, SEAMA NOBUKAZU, 高橋 成実, 海宝 由佳, 小平 秀一

  JpGU-AGU Joint Meeting 2017, May 2017, Japanese, 幕張メッセ, International conference

  Oral presentation


• Tectonics of long-offset oceanic transform faults along the Central Indian Ridge

  沖野 郷子, SEAMA NOBUKAZU, 藤井 昌和, 町田 嗣樹

  JpGU-AGU Joint Meeting 2017, May 2017, Japanese, 幕張メッセ, International conference

  Poster presentation


• Integrated offshore investigations in the vicinity of Kikai Caldera, southwestern Japan -towards a comprehensive understanding of destructive caldera eruptions-

  ICHIHARA HIROSHI, 橋本 順歩, 高橋 大和, 清水 賢, SANO MAMORU, MATSUNO TETSUO, SEAMA NOBUKAZU, 山本 揚二朗, 井和丸 光, 中東 和夫, 若林 伸和, 小平 秀一, TATSUMI YOSHIYUKI

  JpGU-AGU Joint Meeting 2017, May 2017, English, 幕張メッセ, International conference

  Oral presentation


• Geomorphological features of the Southern Mariana Trough spreading center obtained from near-bottom surveys using the AUV Urashima

  岡本 理, SEAMA NOBUKAZU, 沖野 郷子, 本荘 千枝

  JpGU-AGU Joint Meeting 2017, May 2017, English, 幕張メッセ, International conference

  Poster presentation


• Along-trough variation in the seismic structure of the incoming Philippine Sea plate just seaward of the Nankai Trough

  仲西 理子, 山下 幹也, 山本 揚二朗, 藤江 剛, 三浦 誠一, 小平 秀一, 金田 義行, SEAMA NOBUKAZU

  JpGU-AGU Joint Meeting 2017, May 2017, English, 幕張メッセ, International conference

  Poster presentation


• Mantle heterogeneity beneath the Mariana Trough Back-Arc Basin

  Nobukazu Seama

  Collaboration Research in global ocean and subduction, Apr. 2017, English, Seoul National University, International conference

  Oral presentation


• 南東インド洋海嶺近傍における上部マントル比抵抗構造の推定

  川野 由貴, MATSUNO TETSUO, SEAMA NOBUKAZU

  海半球観測研究センター20周年シンポジウム「新たな観測が開く海半球の未来」, Mar. 2017, Japanese, 地震研究所, Domestic conference

  Poster presentation


• 海洋底科学としての太平洋アレイ

  SEAMA NOBUKAZU

  太平洋アレイ（PA）研究会, Sep. 2016, Japanese, 東京大学地震研究所, Domestic conference

  Oral presentation


• Enhanced and asymmetric melting beneath the southern Mariana back-arc spreading ridge, influenced by the subduction of the Pacific plate

  MATSUNO TETSUO, SEAMA NOBUKAZU, Haruka Shindo, Yoshifumi Nogi, Kyoko Okino

  23rd Electromagnetic Induction Workshop, Aug. 2016, English, The Empress Convention Center, International conference

  Poster presentation


• Electrical resistivity structure under the western Cosmonauts Sea at the continental margin of East Antarctica inferred via a marine magnetotelluric experiment

  MATSUNO TETSUO, Yoshifumi Nogi, SEAMA NOBUKAZU

  23rd Electromagnetic Induction Workshop, Aug. 2016, English, The Empress Convention Center, International conference

  Poster presentation


• Electrical resistivity signature of the oceanic crust around hydrothermal vent sites on East Pacific Rise at 9° 50’N

  Takuya Teraoka, SEAMA NOBUKAZU, Rob Evans

  23rd Electromagnetic Induction Workshop, Aug. 2016, English, The Empress Convention Center, International conference

  Oral presentation


• 太平洋プレートの沈み込みの影響を受けた南部マリアナ背弧拡大海嶺下の豊富で非対称な部分溶融

  松野 哲男, SEAMA NOBUKAZU, 新藤 悠, 野木 義史, 沖野 郷子

  日本地球惑星科学連合2016年大会, May 2016, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• フラクチャーゾーン、トランスフォーム断層を横切る深海地磁気調査

  SEAMA NOBUKAZU, 北川 高行, 沖野 郷子, 藤井 昌和, 中東 和夫, 岡本 理, 古川 優和, 小林 拓史, 野木 義史

  日本地球惑星科学連合2016年大会, May 2016, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• KH-15-5 白鳳丸研究航海速報：長大トランスフォーム断層と海嶺活動 CIR13°-18°S

  沖野 郷子, SEAMA NOBUKAZU, 砂村 倫成, 町田 嗣樹, 研究者

  日本地球惑星科学連合2016年大会, May 2016, Japanese, 幕張メッセ, Domestic conference

  Poster presentation


• 沈み込む海洋プレートの違い：新しい視点

  SEAMA NOBUKAZU

  東京大学地震研究所共同利用研究集会, Nov. 2015, Japanese, 東京大学地震研究所, Domestic conference

  Oral presentation


• 海底地震観測による2011年東北地震北部震源域の余震分布

  平井 広大, NAKAHIGASHI KAZUO, SEAMA NOBUKAZU, 村井 芳夫, 日野 亮太, 東 龍介, 伊藤 喜宏, 佐藤 利典, 真保 敬, 町田 祐弥, 山田 知朗, 望月 公廣, 塩原 肇, 植平 賢司, 八木原 寛, 篠原 雅尚

  日本地震学会2015年度秋季大会, Oct. 2015, Japanese, Domestic conference

  Poster presentation


• Review of Japanese geophysical surveys of Indian Ocean Ridges

  SEAMA NOBUKAZU

  2nd InterRidge Workshop: Circum Antarctic Ridges, Oct. 2015, English, Korea Polar Research Institute, International conference

  Oral presentation


• Review of Japanese Taiga project 3, Southern MarianaTrough back-arc basin

  SEAMA NOBUKAZU

  Third InterRidge Theoretical Institute Magmatic and Tectonic Processes and Seabed Resources at Mid-Ocean Ridges, Sep. 2015, English, Hangzhou, China, International conference

  [Invited]

  Invited oral presentation


• Water release from subducting slab inferred by uppermantle electrical resistivity structures beneath back-arc basins

  SEAMA NOBUKAZU, 松野 哲男

  日本地球惑星科学連合2015年大会, May 2015, Japanese, 幕張メッセ国際会議場, Domestic conference

  Oral presentation


• Determining the three-dimensional position of theanomalous resistivity body in upper oceanic crust using MMR method

  寺岡 拓也, SEAMA NOBUKAZU

  日本地球惑星科学連合2015年大会, May 2015, Japanese, 幕張メッセ国際会議場, Domestic conference

  Oral presentation


• Electrical resistivity structure of the oceanic crust around hydrothermal vent sites on East Pacific Rise at N9 50'

  寺岡 拓也, SEAMA NOBUKAZU, Evans Rob

  日本地球惑星科学連合2015年大会, May 2015, Japanese, 幕張メッセ国際会議場, Domestic conference

  Oral presentation


• ノサップフラクチャーゾーンにおける重力・地磁気・海底地形調査の概要

  SEAMA NOBUKAZU, NAKAHIGASHI KAZUO, 飯塚 絵梨, 北川 高行, 藤井 昌和, 沖野 郷子, 野木 義史, 奈須 俊勝

  ブルーアース2015, Mar. 2015, Japanese, 独立行政法人海洋研究開発機構, 東京海洋大学（品川キャンパス）, Domestic conference

  Poster presentation


• Upper mantle electrical resistivity structures beneath the Indian Ocean and back-arc basins

  Nobukazu Seama, Tetsuo Matsuno

  Structure and Dynamics of the Oceanic Lithosphere/Asthenosphere System, Mar. 2015, English, the Normal Oceanic Mantle Project, Hotel Matsushima Taikanso, Miyagi, Japan, International conference

  Poster presentation


• 福島県相馬沖の地震波速度構造調査

  武林 仁樹, NAKAHIGASHI KAZUO, 島 伸和, 佐 藤壮, 藤江 剛, 高橋 努, 三浦 誠一, 小平 秀一

  日本地震学会秋季大会, Nov. 2014, Japanese, Domestic conference

  Poster presentation


• Hydrothermal Heat Mining Due to the Aquifer Thickening Toward the Trench Axis: A Model for Explaining High Heat-flow Anomalies on the Seaward Side of the Japan Trench

  Kawada, Y, Yamano, M, Seama, N

  AOGS 2014, Jul. 2014, English, Sapporo, International conference

  Poster presentation


• Electrical resistivity structure of the Snail site at the Southern Mariana Trough spreading center

  松野 哲男, 木村 真穂, SEAMA NOBUKAZU

  日本地球惑星科学連合2014年大会, May 2014, Japanese, パシフィコ横浜, Domestic conference

  Poster presentation


• Hydrothermal heat mining due to the aquifer thickening toward the trench axis: A model for the Japan Trench

  川田 佳史, 山野 誠, SEAMA NOBUKAZU

  日本地球惑星科学連合2014年大会, May 2014, Japanese, パシフィコ横浜, Domestic conference

  Oral presentation


• Heterogeneity from mantle to crust at the central Southwest Indian Ridge(2)-Crust-

  佐藤 暢, 佐藤 太一, 町田 嗣樹, 仙田 量子, 松野 哲男, SEAMA NOBUKAZU, 中村 謙太郎, 森下 知晃, 野木 義史, 沖野 郷子

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Invited oral presentation


• Heterogeneity from mantle to crust at the central Southwest Indian Ridge(1)-Upper mantle-

  MATSUNO TETSUO, SEAMA NOBUKAZU, 佐藤 暢, 佐藤 太一, 仙田 量子, 町田 嗣樹, 中村 謙太郎, 森下 知晃, 水間 恵子, 野木 義史, 沖野 郷子

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Oral presentation


• Upper mantle electrical resistivity structure at the continental margin of East Antarctica

  松野 哲男, 野木 義史, SEAMA NOBUKAZU

  日本地球惑星科学連合2014年大会, Apr. 2014, Japanese, パシフィコ横浜, Domestic conference

  Poster presentation


• 南マリアナトラフ背弧海盆の海底拡大系における地球物理学調査

  SEAMA NOBUKAZU, 新藤 悠, 佐藤利典, 水野真理子, 高田裕能, 松野哲男, 野木義史, 吉河 秀郎, 沖野郷子, 山田知朗, 一瀬建日, 望月公廣, 篠原雅尚

  ブルーアース2014, Feb. 2014, Japanese, 東京海洋大学品川キャンパス, Domestic conference

  Oral presentation


• QUELLE2013航海報告－Quest 1：インド洋

  西澤 学, 中村 謙太郎, SEAMA NOBUKAZU, 高井 研, 渡部 裕美, 次航海乗船研究者一同

  ブルーアース2014, Feb. 2014, Japanese, 東京海洋大学品川キャンパス, Domestic conference

  Oral presentation


• Seismic structure and seismicity around the hydrothermal area in the Souther Mariana Trough

  佐藤 利典, 水野 真理子, 高田 裕能, 山田 知朗, 一瀬 建日, 望月 公廣, 篠原 雅尚, 島 伸和

  海底拡大系の総合研究：現状と将来 -InterRidge-Japan研究集会-, Nov. 2013, Japanese, 東京大学大気海洋研究所, Domestic conference

  Oral presentation


• Upper mantle electrical resistivity structure beneath the Southwest Indian Ridge 37º

  Tetsuo MATSUNO, Keiko MIZUMA, Nobukazu SEAMA, Yoshifumi NOGI, Kyoko OKINO

  “Mid-ocean ridges and hydrothermal activity in the Indian Ocean” joint-hosted by Japan-Korea Marine Geoscience Symposium on Global Open Ocean Studies, Nov. 2013, English, 東京大学大気海洋研究所, International conference

  Oral presentation


• Geophysical investigations of Rodriguez Triple Junction and southern Mariana Trough back-arc basin

  Nobukazu SEAMA, Tomoaki YAMADA, Toshinori SATO, Tetsuo MATSUNO, Taichi SATO, Eri IIZUKA, Haruka SHINDO, Yui NOGUGHI, Takahiro BABA, Akihiro KONO, Hirohoshi TAKADA, Takehi ISSE, Kyoko OKINO, Masanao SHINOHARA, Yoshifumi NOGI, Kimihiro MOCHIZUKI, Takeshi TSUJI

  “Mid-ocean ridges and hydrothermal activity in the Indian Ocean” joint-hosted by Japan-Korea Marine Geoscience Symposium on Global Open Ocean Studies, Nov. 2013, English, 東京大学大気海洋研究所, International conference

  Oral presentation


• Electrical resistivity structure under the Cosmonauts Sea offshore East Antarctica

  松野 哲男, 野木 義史, SEAMA NOBUKAZU

  地球電磁気・地球惑星圏学会第134回総会・講演会, Nov. 2013, Japanese, 高知大学, Domestic conference

  Poster presentation


• Geophysical results of the Southern Mariana Trough back-arc basin: From mantle to hydrothermal vent sites

  SEAMA NOBUKAZU, 沖野 郷子, 野木 義史, 佐藤 利典, 松野 哲男, 吉河 秀郎, 望月 伸竜, 篠原 雅尚

  日本地球惑星科学連合2013年大会, May 2013, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• Thermal subduction-zone model including hydrothermal circulation in an aquifer that thickened toward the trench axis

  川田 佳史, 山野 誠, SEAMA NOBUKAZU

  日本地球惑星科学連合2013年大会, May 2013, Japanese, 日本地球惑星科学連合, 幕張メッセ, Domestic conference

  Oral presentation


• マルチスケールで見た海底拡大系

  SEAMA NOBUKAZU

  ２１世紀の人間活動と資源，環境に関連した地球科学に関するシンポジウム, May 2013, Japanese, 東京大学理学部小柴ホール, Domestic conference

  Oral presentation


• Tectonic background of a unique hydrogen-rich Kairei Hydrothermal Field, Central Indian Ridge: Results from Taiga Projec

  沖野 郷子, 中村 謙太郎, 森下 知晃, 佐藤 暢, 佐藤 太一, 望月 伸竜, 辻 健, SEAMA NOBUKAZU

  日本地球惑星科学連合2013年大会, May 2013, Japanese, 幕張メッセ, Domestic conference

  Oral presentation


• Upper mantle electrical resistivity structure beneath the Southwest Indian Ridge 37°E

  MATSUNO Tetsuo, MIZUMA Keiko, SEAMA Nobukazu, NOGI Yoshifumi, OKINO Kyoko

  2012 AGU Fall Meeting, Dec. 2012, English, AGU, San Francisco, USA, International conference

  Poster presentation


• Mantle to hydrothermal vent sites of the Southern Mariana Trough back-arc Basin: Results from the Taiga Project

  SEAMA Nobukazu, OKINO Kyoko, NOGI Yoshifumi, SATO Toshinori, MATSUNO Tetsuo, YOSHIKAWA Shuro, MOCHIZUKI Nobutatsu, SHINOHARA Masanao

  2012 AGU Fall Meeting, Dec. 2012, English, AGU, San Francisco, USA, International conference

  Oral presentation


• Electrical resistivity structure of the upper mantle in the Southern Mariana Trough

  SHINDO Haruka, SEAMA Nobukazu, MATSUNO Tetsuo, SHIBATA Yuki, KIMURA Maho, NOGI Yoshifumi, OKINO Kyoko

  2012 AGU Fall Meeting, Dec. 2012, English, AGU, San Francisco, USA, International conference

  Poster presentation


• 最近の海底拡大系の地球物理学的知見と海底に眠る磁化構造・古地磁気の課題

  SEAMA Nobukazu

  2012年地磁気・古地磁気・岩石磁気夏の学校, Sep. 2012, Japanese, 地磁気・古地磁気・岩石磁気研究会, 兵庫県立但馬長寿の郷，兵庫, Domestic conference

  Invited oral presentation


• 南マリアナトラフ拡大軸にある海底熱水系下の比抵抗構造推定

  KIMURA Maho, SEAMA Nobukazu, MATSUNO Tetsuo, TADA Noriko

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張メッセ,千葉, Domestic conference

  Poster presentation


• 南マリアナトラフにおける上部マントルの比抵抗構造

  SHINDO Haruka, SEAMA Nobukazu, MATSUNO Tetsuo, KIMURA Maho, SHIBATA Yuki, OKINO Kyoko, NOGI Yoshifumi

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張メッセ,千葉, Domestic conference

  Poster presentation


• 中部マリアナ背弧拡大軸下のマントル溶融域に対する電磁気学的な制約

  MATSUNO Tetsuo, EVANS, R.L, SEAMA Nobukazu

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張メッセ,千葉, Domestic conference

  Oral presentation


• ラウ背弧海盆下の比抵抗構造の推定

  SHIBATA Yuki, SEAMA Nobukazu, MIZUMA Keiko, KIMURA Maho, KOBAYASHI Seiya, MATSUNO Tetsuo, NOGI Yoshifumi

  日本地球惑星科学連合2012年大会, May 2012, Japanese, 日本地球惑星科学連合, 幕張メッセ,千葉, Domestic conference

  Oral presentation


• Tectonic evolution, magmatic activity variation, and mantle dynamics of Mariana Trough back-arc basin

  SEAMA Nobukazu

  Mariana Vent Larvae (MarVel) Workshop: International Study of Connectivity Between Hydrothermal Vents, May 2012, English, Mariana Vent Larvae, Okinawa，Japan, International conference

  Invited oral presentation


• Electrical resistivity structural images beneath sea-floor spreading centers

  SEAMA Nobukazu

  The First Korea-Japan Marine Gepsciences Symposium, Apr. 2012, English, Seoul，Korea, International conference

  Oral presentation


• 深海底熱水活動域に生息する化学合成微生物の遺伝学的多様性と群集構造の解明

  美野 さやか, 中川 聡, 澤辺 智雄, 宮崎 淳一, 牧田 寛子, 和辻 智朗, 中村 謙太郎, 加藤 真悟, 小島 茂明, 渡部 裕美, 土岐 知弘, 島 伸和, 石橋 純一郎, 布浦 拓郎, 山本 正浩, 高井 研, 乗船研究者一同

  ブルーアース2012, Feb. 2012, Japanese, 海洋研究開発機構, 東京海洋大学，東京, Domestic conference

  Poster presentation


• Upper mantle electrical resistivity structure beneath back-arc spreading centers

  Seama, N, Shibata, Y, Kimura, M, Shindo, H, Matsuno, T, Nogi, Y, Okino, K

  2011 AGU Fall Meeting, Dec. 2011, English, AGU, San Francisco, USA, International conference

  Oral presentation


• Constraint on a melting regime in upper mantle beneath the central Mariana back-arc spreading center through the geophysical electromagnetic forward modeling

  Matsuno, T, Evans, R.L, Seama, N

  2011 AGU Fall Meeting, Dec. 2011, English, AGU, San Francisco, USA, International conference

  Poster presentation


• 南マリアナトラフ拡大軸にある海底熱水系下の電気伝導度構造

  木村 真穂, 島 伸和, 松野 哲男, 多田 訓子

  地球電磁気・地球惑星圏学会第130回総会・講演会, Nov. 2011, Japanese, 地球電磁気・地球惑星圏学会, 神戸大学，兵庫, Domestic conference

  Oral presentation


• ラウ背弧海盆下の2次元比抵抗構造の推定

  柴田 侑希, 島 伸和, 野木 義史, 松野 哲男, 木村 真穂

  地球電磁気・地球惑星圏学会第130回総会・講演会, Nov. 2011, Japanese, 地球電磁気・地球惑星圏学会, 神戸大学，兵庫, Domestic conference

  Oral presentation


• 沈み込む前後の地殻で起こる熱水循環の数値計算：日本海溝海側の高熱流量異常への応用

  川田 佳史, 山野 誠, 島 伸和

  日本地震学会2011年度秋季大会, Oct. 2011, Japanese, 日本地震学会, 静岡県コンベンションアーツセンター・グランシップ，静岡, Domestic conference

  Poster presentation


• Estimation of 2-D resistivity structure beneath the Lau back-arc Basin

  Shibata, Y, Seama, N, Mizuma, K, Kimura, M, Kobayashi, S, Matsuno, T, Nogi, Y

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Poster presentation


• Electrical conductivity structure of the upper mantle beneath in the southern Mariana Trough

  Shindo, H, Seama, N, Kimura, M, Shibata, Y, Matsuno, T, Nogi, Y, Okino, K

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Poster presentation


• Electrical conductivity structure of a seafloor hydrothermal system at the southern Mariana Trough spreading axis

  Kimura, M, Seama, N, Matsuno, T, Tada, N

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Poster presentation


• Development of a 3-Dimensional Forward Program for Magnetometric Resistivity Method: Application to Alice Springs Field

  Tada, N, Kido, M, Seama, N

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Poster presentation


• Constraint on a melting regime in upper mantle beneath the central Mariana back-arc spreading center through the geophysical electromagnetic forward modeling

  Matsuno, T, Evans, R.L, Seama, N

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Poster presentation


• Comparison among available electrical resistivity structural images beneath back-arc and mid-ocean ridge spreading centers

  Seama, N

  Workshop on Ocean Mantle Dynamics: from Spreading Center to Subduction Zone, Oct. 2011, English, Chiba, Japan, International conference

  Invited oral presentation


• 海洋プレートが沈み込む前後に起こる熱水循環はプレート内の温度分布をどう変えるか？

  川田 佳史, 山野 誠, 島 伸和

  東京大学地震研究所共同利用研究集会「沈み込み帯の温度構造と地震活動・変形過程」, Sep. 2011, Japanese, 東京大学地震研究所, 東京大学，東京, Domestic conference

  Oral presentation


• 南西インド洋中央海嶺35E-40E における地球物理観測から見る火成活動および断層活動のセグメント内での変化

  佐藤 太一, 沖野 郷子, 島 伸和, 佐藤 暢, 中村 謙太郎, 仙田 量子, 町田 嗣樹

  日本地球惑星科学連合2011年大会, May 2011, Japanese, 日本地球惑星科学連合, 幕張メッセ，千葉, Domestic conference

  Oral presentation


• 小笠原海台南東の北西太平洋海盆における地震波速度構造

  辻野 良輔, 藤江 剛, 島 伸和, 小平 秀一, 西澤 あずさ, 金田 謙太郎

  日本地球惑星科学連合2011年大会, May 2011, Japanese, 日本地球惑星科学連合, 幕張メッセ,千葉, Domestic conference

  Oral presentation


• 南マリアナトラフ背弧海盆拡大系における地球物理学的調査

  島 伸和, 佐藤 利典, 一瀬 建日, 山田 知朗, 水野 真理子, 木村 真穂, 柴田 侑希, 新藤 悠, 沖野 郷子, 篠原 雅尚, 望月 公廣, 野木 義史, 辻 健, 松野 哲男, 岡田 聡, 樋泉 昌之, 高江洲 盛史, 岩本 久則

  ブルーアース'11, Mar. 2011, Japanese, 東京, Domestic conference

  Oral presentation


• 海底拡大系下の上部マントル比抵抗構造

  島 伸和

  東京大学地震研究所特定共同研究B研究集会「地球内部境界層の構造と全地球ダイナミクス」, Mar. 2011, Japanese, 東京, Domestic conference

  Oral presentation


• ラウ背弧海盆拡大系における長期海底電磁場観測の概要

  島 伸和, 柴田 侑希, 木村 真穂, 水間 恵子, 松野 哲男, 小林 聖也, 野木 義史

  2010年度CA研究会, Feb. 2011, Japanese, 京都, Domestic conference

  Oral presentation


• The MoHole: a Crustal Journey and Mantle Quest

  Ildefonse, B, Abe, N, Isozaki, Y, Blackman, D.K, Canales, J.P, Kodaira, S, Myers, G, Nakamura, K, Nedimovic, M.R, Seama, N, Teagle, D.A.H, Umino, S, Wilson, D.S, Yamao, M

  2010 AGU Fall meeting, Dec. 2010, English, USA, International conference

  Poster presentation


• 地球物理観測に基づく南西インド洋海嶺東経35-40度における断層活動とメルト供給量に関する研究

  島 伸和

  海底拡大系の総合研究－InterRidge Japan研究発表集会－, Nov. 2010, Japanese, 千葉, Domestic conference

  Oral presentation


• 海底拡大系の上部マントル比抵抗構造－これまでの研究と今後－

  佐藤 太一, 沖野 郷子, 島 伸和

  海底拡大系の総合研究－InterRidge Japan研究発表集会－, Nov. 2010, Japanese, 千葉, Domestic conference

  Oral presentation


• モホールに向けて-掘削候補地の選定-

  島 伸和, 富士原 敏也, 阿部 なつ江, 小平 秀一, 巽 好幸, 海野 進, 荒井 章司

  日本地質学会第117年学術大会, Sep. 2010, Japanese, 富山, Domestic conference

  Invited oral presentation


• 海底拡大系のダイナミクス

  島 伸和

  海洋技術創出シンポジウム, Jul. 2010, Japanese, 大阪, Domestic conference

  Oral presentation


• Hawaii site in comparison with IODP site 1256

  Seama, N

  The International Workshop on The MoHole: A Crustal Journey and Mantle Quest, Jun. 2010, English, 金沢, International conference

  Invited oral presentation


• 南西インド洋海嶺37°Ｅにおける上部マントル比抵抗構造の推定

  水間 恵子, 島 伸和, 辻野 良輔, 野木 義史, 沖野 郷子

  日本地球惑星科学連合2010年大会, May 2010, Japanese, 千葉, Domestic conference

  Oral presentation


• 南西インド洋海嶺34-40Eの超低速拡大セグメントの地球物理学的研究（KH0704-Leg2 and KH0905-Leg4）

  佐藤 太一, 沖野 郷子, 島 伸和, 羽入 朋子, 水野 真理子, 小嶋 孝徳, 奥村 智

  日本地球惑星科学連合2010年大会, May 2010, Japanese, 千葉, Domestic conference

  Oral presentation


• Marine magnetotelluric survey across the Southwest Indian Ridge 37°E

  Seama, N, Mizuma, K, Tsujino, R, Nogi, Y, Okino, K

  European Geoscience Union General Assembly 2010, May 2010, English, Austria, International conference

  Poster presentation


• 南西インド洋海嶺37°Eにおける上部マントル電気伝導度構造の推定

  水間 恵子, 島 伸和, 辻野 良輔, 野木 義史, 沖野 郷子

  2009年度CA研究会, Feb. 2010, Japanese, 東京, Domestic conference

  Oral presentation


• 南西インド洋海嶺、東経37度における電気伝導度構造探査

  水間 恵子, 島 伸和, 辻野 良輔, 野木 義史, 沖野 郷子

  東京大学海洋研究所共同利用研究集会 海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2009, Japanese, 東京, Domestic conference

  Oral presentation


• Mohole 掘削に向けた地球物理学的研究 －戦略と計画－

  小平 秀一, 島 伸和

  日本地震学会2009年秋季大会, Oct. 2009, Japanese, 京都, Domestic conference

  Oral presentation


• 北太平洋白亜紀海洋地殻の磁気異常－白亜紀スーパークロンの古地磁気強度変動の研究－

  望月 伸竜, 山崎 俊嗣, 木村 真穂, 石原 丈実, 島 伸和, 野木 義史

  地球電磁気・地球惑星圏学会第126回講演会, Sep. 2009, Japanese, 石川, Domestic conference

  Oral presentation


• Japanese Marine Geophysical and Geological ResearchActivities in the Antarctic Ocean

  Nogi, Y, Miura, H, Ikehara, M, Seama, N

  16th International Symposium on Polar Sciences, Jun. 2009, English, South Korea, International conference

  Poster presentation


• 南西インド洋海嶺34°－40°Eに位置する斜交拡大海嶺の地球物理的研究

  佐藤 太一, 沖野 郷子, 野木 義史, 島 伸和

  日本地球惑星科学連合2009年大会, May 2009, Japanese, 千葉, Domestic conference

  Poster presentation


• 東南極大陸縁辺域リュツオ・ホルム湾沖での海底電磁気探査

  松野 哲男, 野木 義史, 北田 数也, 島 伸和, 岡田 浩一

  日本地球惑星科学連合2009年大会, May 2009, Japanese, 千葉, Domestic conference

  Oral presentation


• Towing bipole electric current for marine magnetometric resistivity method

  島 伸和, 後藤 忠徳, 多田 訓子, 下泉 政志

  日本地球惑星科学連合2009年大会, May 2009, Japanese, 千葉, Domestic conference

  Oral presentation


• 南極大陸縁辺域における海底下比抵抗構造探査

  松野 哲男, 野木 義史, 北田 数也, 島 伸和, 岡田 浩一

  CA研究会, Feb. 2009, Japanese, 京都, Domestic conference

  Oral presentation


• Electrical structure in the mantle across the Mariana subduction system

  MATSUNO Tetsuo, SEAMA Nobukazu, BABA Kiyoshi, GOTO Tada-nori, CHAVE Alan, EVANS Rob L, WHITE Antony, BOREN Goran, YONEDA Asami, UTADA Hisashi, GRAHAM Heinson, SUYEHIRO Kiyoshi

  Final SSP International Symposium on Deep Slab and Mantle Dynamics, Feb. 2009, English, 京都，日本, International conference

  Poster presentation


• 海底地殻を冷却する『煙突』としての海山：数値実験による考察

  川田 佳史, 島 伸和, 浦辺 徹郎

  東京大学海洋研究所共同利用研究集会 海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2008, Japanese, 東京, Domestic conference

  Oral presentation


• ホットスポット影響下の南西インド洋海嶺（東経34 度‐40 度）における地球物理マッピング探査

  佐藤 太一, 沖野 郷子, 島 伸和

  東京大学海洋研究所共同利用研究集会 海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2008, Japanese, 東京, Domestic conference

  Oral presentation


• PS 変換波を用いた海洋地殻内S 波速度構造の推定

  辻野 良輔, 小平 秀一, 金田 謙太郎, 西澤 あずさ, 島 伸和

  東京大学海洋研究所共同利用研究集会 海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2008, Japanese, 東京, Domestic conference

  Oral presentation


• 南極プレート周辺の海底拡大系の研究 その１：南東インド洋海嶺と南極-オーストラリア間のプレート運動の研究

  島 伸和, 沖野 郷子, 野木 義史

  第２回南極研究観測シンポジウム, Jun. 2008, Japanese, 東京, Domestic conference

  Oral presentation


• 北太平洋白亜紀海洋地殻の磁気異常―白亜紀スーパークロンにおける地球磁場強度変動の研究―

  望月 伸竜, 山崎 俊嗣, 木村 真穂, 石原 丈実, 島 伸和, 野木 義史

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Oral presentation


• 白鳳丸KH-07-4 Leg 2による南西インド海嶺34-40°E航海の概要

  島 伸和, 佐藤 利典, 佐藤 暢, 佐藤 太一, 町田 嗣樹, 中村 謙太郎, 仙田 量子, 根尾 夏紀, 北村 貴幸, 水野 真理子, 竹本 帝人, 辻野 良輔, 水間 恵子, 亀尾 桂, 宗 輝, 菅野 真人, 野木 義史, 熊谷 英憲, 篠原 雅尚, 望月 公廣

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Oral presentation


• 白鳳丸KH-07-4 Leg 2による南西インド海嶺34-40°E航海で採取された火山岩類の岩石学・地球化学

  佐藤 暢, 仙田 量子, 中村 謙太郎, 町田 嗣樹, 根尾 夏紀, 熊谷 英憲, 島 伸和, 沖野 郷子

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Poster presentation


• 中部マリアナ沈み込み・前弧・島弧・背弧系の比抵抗構造

  松野 哲男, 島 伸和, 馬場 聖至, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Oral presentation


• 航空機重力異常から推定したゴンドワナ大陸の分裂に伴うリュツォ・ホルム湾周辺の大陸－海洋境界の地殻厚さ変化

  北田 数也, 野木 義史, 島 伸和, Jokat Wilfried

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Oral presentation


• PS変換波を用いた海洋地殻内S波速度構造の推定

  辻野 良輔, 金田 謙太郎, 島 伸和, 西澤 あずさ

  日本地球惑星科学連合2008年大会, May 2008, Japanese, 千葉, Domestic conference

  Oral presentation


• Preliminary report of surface geophysical survey at Southwest Indian Ridge 34-40E cruise (KH0704-Leg2)

  佐藤 太一, 島 伸和, 沖野 郷子, 佐藤 利典, 佐藤 暢, 町田 嗣樹, 中村 謙太郎, 仙田 量子, 根尾 夏紀, 北村 貴幸, 水野 真理子, 竹本 帝人, 辻野 良輔, 水間 恵子, 亀尾 桂, 宗 輝, 菅野 真人

  日本地球惑星科学連合2008年大会, May 2008, English, 千葉, Domestic conference

  Poster presentation


• 沈み込み・前弧・島弧・背弧系（中部マリアナ海域）の電気伝導度構造

  島 伸和, 松野 哲男, 岩本 久則, 辻野 良輔, 後藤 忠徳, 末広 潔, 馬場 聖至, 馬場 祐太, 米田 朝美, 歌田 久司, Alan Chave, Rob L. Evans, Antony White, Goran Boren, Graham Heinson

  第24回しんかいシンポジウム, Mar. 2008, Japanese, 横浜, Domestic conference

  Oral presentation


• マリアナ背弧拡大系の比抵抗構造-東太平洋中央海膨との比較-

  島 伸和, 松野 哲男, 馬場 聖至, 後藤 忠徳, Alan Chave, Antony White, Goran Boren, Rob L. Evans, 米田 朝美, 歌田 久司, 末広 潔, Graham Heinson

  東京大学海洋研究所共同利用研究集会海洋リソスフェア学シンポジウム-海洋底深部構造と進化過程解明に向けて-, Mar. 2008, Japanese, 東京, Domestic conference

  Oral presentation


• 中部マリアナ沈み込み・前弧・島弧・背弧系の電気伝導度構造

  松野 哲男, 島 伸和, 馬場 聖至, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren, 米田 朝美, Graham Heinson, 岩本 久則, 辻野 良輔, 馬場 祐太, 歌田 久司, 末広 潔

  CA研究会, Dec. 2007, Japanese, 東京, Domestic conference

  Oral presentation


• Microearthquake seismicity of the central Mariana Spreading Center

  Iwamoto, H, Wiens, D.A, Barklage, M, Shiobara, H, Sugioka, H, Seama, N

  Joint NSF-MARGINS and IFREE Workshop: Subduction Factory Studies in the Izu-Bonin-Mariana Arc System: Results and Future Plans, Nov. 2007, English, Hawaii, International conference

  Poster presentation


• Imaging mantle structure of the central Mariana subduction-arc-back arc system using marine magnetotellurics

  Seama, N, White, A, Chave, A, Baba, K, Goto, T, Matsuno, T, Evans, R.L, Boren, G, Yoneda, A, Iwamoto, H, Tsujino, R, Baba, Y, Utada, H, Heinson, G, Suyehiro, K

  Joint NSF-MARGINS and IFREE Workshop: Subduction Factory Studies in the Izu-Bonin-Mariana Arc System: Results and Future Plans, Nov. 2007, English, Hawaii, International conference

  Invited oral presentation


• Electrical structure in the mantle across the Mariana subduction system

  Matsuno, T, Seama, N, Baba, K, Goto, T, Chave, A, Evans, R.L, White, A, Boren, G, Yoneda, A, Utada, H, Heinson, G, Suyehiro, K

  Final SSP International Symposium on Deep Slab and Mantle Dynamics, Nov. 2007, English, 京都, International conference

  Poster presentation


• 中部マリアナ沈み込み・前弧・島弧・背弧系の電気伝導度構造

  松野 哲男, 島 伸和, 馬場 聖至, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren, 米田 朝美, Heinson Graham, 岩本 久則, 辻野 良輔, 馬場 祐太, 歌田 久司, 末広 潔

  特定領域研究「地球深部スラブ」第3回研究シンポジウム, Oct. 2007, Japanese, 松山, Domestic conference

  Poster presentation


• 中部マリアナ沈み込み・前弧・島弧・背弧系の電気伝導度構造

  松野 哲男, 島 伸和, 馬場 聖至, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren, 米田 朝美, Heinson Graham, 岩本 久則, 辻野 良輔, 馬場 祐太, 歌田 久司, 末広 潔

  海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2007, Japanese, 東京, Domestic conference

  Oral presentation


• 中部マリアナ海域における海底地磁気変換関数

  米田 朝美, 馬場 聖至, 歌田 久司, 島 伸和, 松野 哲男, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren, Heinson Graham

  東京大学海洋研究所共同利用研究集会 海底拡大系の総合研究-InterRidge-Japan研究発表集会-, Oct. 2007, Japanese, 東京, Domestic conference

  Oral presentation


• ゴンドワナの初期分裂時の東アフリカ沖モザンビーク海盆の海洋底拡大過程

  北田 数也, Jokat Wilfried, 野木 義史, 島 伸和, Koenig Matthias

  第27回極域地学シンポジウム, Oct. 2007, Japanese, 東京, Domestic conference

  Oral presentation


• Seafloor GDS analysis in the central Mariana area

  米田 朝美, 馬場 聖至, 歌田 久司, 島 伸和, 松野 哲男, 後藤 忠徳, Rob L. Evans, Alan Chave, Goran Boren, Antony White, Heinson Graham

  地球電磁気・地球惑星圏学会第122回講演会, Sep. 2007, English, 名古屋, Domestic conference

  Oral presentation


• MMR法による新潟沖メタンハイドレートの３次元イメージング

  大塚 宏徳, 島 伸和, 後藤 忠徳

  地球電磁気・地球惑星圏学会第122回講演会, Sep. 2007, English, 名古屋, Domestic conference

  Oral presentation


• 南極プレート周辺の海底拡大系の研究

  島 伸和, 沖野 郷子, 原田 靖, 野木 義史

  南極研究観測シンポジウム, Jun. 2007, Japanese, 東京, Domestic conference

  Oral presentation


• 南インド洋東エンダビー海盆の地磁気異常

  野木 義史, 北田 数也, 島 伸和

  日本地球惑星科学連合2007年大会, May 2007, Japanese, 千葉, Domestic conference

  Oral presentation


• 中部マリアナトラフ拡大軸付近の震源分布

  岩本 久則, Wiens Douglas A, Barklage Mitchell, 塩原 肇, 杉岡 裕子, 島 伸和

  日本地球惑星科学連合2007年大会, May 2007, Japanese, 千葉, Domestic conference

  Oral presentation


• ゴンドワナの初期分裂時の東アフリカ沖モザンビーク海盆の海洋底拡大過程

  北田 数也, Koenig Matthias, Jokat Wilfried, 野木 義史, 島 伸和

  日本地球惑星科学連合2007年大会, May 2007, Japanese, 千葉, Domestic conference

  Oral presentation


• Preliminary results of marine magnetotelluric analysis across the central Mariana transect

  松野 哲男, 島 伸和, 馬場 聖至, 後藤 忠徳, Alan Chave, Rob L. Evans, Antony White, Goran Boren, 米田 朝美, 岩本 久則, 辻野 良輔, 馬場 祐太, 歌田 久司, 末広 潔

  日本地球惑星科学連合2007年大会, May 2007, English, 千葉, Domestic conference

  Oral presentation


• MMR法による海底熱水循環系の3 次元比抵抗構造の推定

  多田 訓子, 島 伸和, 木戸 元之

  日本地球惑星科学連合2007年大会, May 2007, Japanese, 千葉, Domestic conference

  Oral presentation


• 沈み込み・前弧・島弧・背弧系（中部マリアナ海域）の海底ＭＴ横断探査（序報）

  松野 哲男, 島 伸和, 岩本 久則, 辻野 良輔, 馬場 聖至, 米田 朝美, 馬場 祐太, 歌田 久司, 後藤 忠徳, 末広 潔, Alan Chave, Rob L. Evans, Antony White, Goran Boren

  ＣＡ研究会, Mar. 2007, Japanese, 京都, Domestic conference

  Oral presentation


• 沈み込み・前弧・島弧・ 背弧系(中部マリアナ海域)の海底MT横断探査(序報)

  松野 哲男, SEAMA NOBUKAZU, 岩本 久則, 辻野 良輔, 馬場 聖至, 米田 朝美, 馬場 祐太, 歌田 久司, 後藤 忠徳, 末広 潔, Alan Chave, Rob L. Evans, Antony White, Goran Boren

  CA研究会, Mar. 2007, Japanese, 日本, Domestic conference

  Oral presentation


• 海底電位差磁力計による沈み込み・前弧・島弧・背弧系（中部マリアナ海域）の横断探査の概要

  島 伸和, 松野 哲男, 岩本 久則, 辻野 良輔, 馬場 聖至, 馬場 祐太, 米田 朝美, 歌田 久司, 後藤 忠徳, 末広 潔, Alan Chave, Rob L. Evans, John Bailey, Alan Gardner, Helmut Moeller, Antony White, Goran Boren, 鈴木 啓吾, 小村 舞, 青木 美澄, 井戸 美帆

  第23回しんかいシンポジウム, Mar. 2007, Japanese, 横浜, Domestic conference

  Poster presentation


• 海底電位差磁力計による沈み込 み・前弧・島弧・背弧系(中部マリアナ海域)の横断探査の概要

  SEAMA NOBUKAZU, 松野 哲男, 岩本 久則, 辻野 良輔, 馬場 聖至, 馬場 祐太, 米田 朝美, 歌田 久司, 後藤 忠徳, 末広 潔, Alan Chave, Rob L. Evans, John Bailey, Alan Gardner, Helmut Moeller, Anthony White, Goran Boren, 鈴木 啓吾, 小村 舞, 青木 美澄, 井戸 美帆

  第 23 回しんかいシンポジウム, Mar. 2007, Japanese, 日本, Domestic conference

  Poster presentation


• MMR 法の 3 次元フォワード解析手法と海底熱水循環系への応用

  多田 訓子, SEAMA NOBUKAZU, 木戸 元之

  CA研究会, Mar. 2007, Japanese, 日本, Domestic conference

  Oral presentation


• MMR法の3次元フォワード解析手法と海底熱水循環系への応用

  多田 訓子, 島 伸和, 木戸 元之

  ＣＡ研究会, Mar. 2007, Japanese, 京都, Domestic conference

  Oral presentation


• 中部マリアナトラフ拡大軸上にある海底熱水循環系の３次元電気伝導度構造

  多田 訓子, 島 伸和, 木戸 元之

  東京大学海洋研究所共同利用研究集会中央海嶺研究のグローバルな展開-InterRidge-Japan研究発表集会-, Nov. 2006, Japanese, 東京, Domestic conference

  Oral presentation


• 中部マリアナトラフ拡大軸上にある海底熱水循環系の3次元電気 伝導度構造

  多田 訓子, SEAMA NOBUKAZU, 木戸 元之

  東京大学海洋研究所共同利用研究集会中央海嶺研究のグローバルな展開-InterRidge-Japan 研究発表集会-, Nov. 2006, Japanese, 日本, Domestic conference

  Oral presentation


• 海底地震計より求めた中部マリアナトラフ拡大軸付近の震源分布

  岩本 久則, Douglas Wiens, Mitchell Barklage, 塩原 肇, 杉岡 裕子, 島 伸和

  東京大学海洋研究所共同利用研究集会中央海嶺研究のグローバルな展開-InterRidge-Japan研究発表集会-, Nov. 2006, Japanese, 東京, Domestic conference

  Oral presentation


• 海底地震計より求めた中部マリアナトラフ拡大軸付近の震源分布

  岩本 久則, Douglas Wiens, Mitchell Barklage, 塩原 肇, 杉岡 裕子, SEAMA NOBUKAZU

  東京大学海洋研究所共同利用研究集会中央海嶺研究のグローバルな展開-InterRidge-Japan 研究発表集会-, Nov. 2006, Japanese, 日本, Domestic conference

  Oral presentation


• Undulation of 410-km discontinuity beneath the Philippine Sea plate as inferred from geomagnetic vertical gradient sounding method.

  Toh, H, A. Hibino, T. Goto, H. Utada, Nobukazu Seama

  18th International Workshop on Electromagnetic Induction in the Earth El Vendrell - 2006, Sep. 2006, English, スペイン, International conference

  Poster presentation


• Undulation of 410-km discontinuity beneath the Philippine Sea plate as inferred from geomagnetic vertical gradient sounding method

  TOH H, HIBINO A, GOTO T, UTADA H, SEAMA Nobukazu

  18th International Workshop on Electromagnetic Induction in the Earth El Vendrell - 2006, Sep. 2006, English, Spain, International conference

  Oral presentation


• A newly developed three-dimensional forward program for the Magnetometric Resistivity method.

  Tada N, M. Kido, Nobukazu Seama

  18th International Workshop on Electromagnetic Induction in the Earth El Vendrell - 2006, Sep. 2006, English, スペイン, International conference

  Poster presentation


• A newly developed three-dimensional forward program for the Magnetometric Resistivity method

  TADA N, KIDO M, SEAMA N

  18th International Workshop on Electromagnetic Induction in the Earth El Vendrell - 2006, Sep. 2006, English, Spain, International conference

  Poster presentation


• Investigation of Sub-vent Biosphere through Aseptic Drilling into Arc and Backarc Volcanoes.

  Urabe, T, Nobukazu Seama, K. Marumo, A. Maruyama, J. Ishibashi, Archaean Park Research Group

  Ridge Theoretical Institute Meeting, Jun. 2006, English, アメリカ, International conference

  Poster presentation


• Investigation of Sub-vent Biosphere through Aseptic Drilling into Arc and Backarc Volcanoes

  URABE T, SEAMA N, MARUMO K, MARUYAMA A, ISHIBASHI J, Archaean Park Research Group

  Ridge Theoretical Institute Meeting, Jun. 2006, English, Mammoth Lakes, CA, USA, International conference

  Poster presentation


• 日本海新潟沖ガスハイドレート域でのMMR法電磁探査

  島 伸和, 後藤 忠徳, 松野 哲男, 岩本 久則, 笠谷 貴史, 大塚 宏徳, 高木 亮, 岡本 拓, 多田 訓子, 渡辺 俊樹, 真田 佳典, 三ケ田 均

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Oral presentation


• 地磁気鉛直勾配法で見たフィリピン海プレート下の４１０ｋｍ不連続面

  藤 浩明, 日比野 明夫, 後藤 忠徳, 歌田 久司, 島 伸和

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Oral presentation


• 地磁気鉛直勾配法で見たフィリピン海プレート下の410km不連続面

  藤 浩明, 日比野 明夫, 後藤 忠徳, 歌田 久司, SEAMA NOBUKAZU

  日本地球 惑星科学連合 2006 年大会, May 2006, Japanese, 日本, Domestic conference

  Oral presentation


• 海底電気探査によるメタンハイドレートイメージングの試み

  高木 亮, 後藤 忠徳, 笠谷 貴史, 渡辺 俊樹, 岡本 拓, 真田 佳典, 三ケ田 均, 島 伸和

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Oral presentation


• 海底電位差磁力計による沈み込み・前弧・島弧・背弧系（中部マリアナ海域）の横断探査

  島 伸和, 馬場 聖至, CHAVE Alan, WHITE Anthony, 岩本 久則, 松野 哲男, 馬場 祐太, BOREN Goran, 後藤 忠徳, 歌田 久司, 末広 潔

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Oral presentation


• 海底電位差磁力計による沈み込み・前弧・島弧・背弧系(中部マリ アナ海域)の横断探査

  SEAMA NOBUKAZU, 馬場聖至, Chave Alan, White Anthony, 岩本久則, 松野哲男, 馬場祐太, Boren Goran, 後藤忠徳, 歌田久司, 末広潔

  日本地球 惑星科学連合 2006 年大会, May 2006, Japanese, 日本, Domestic conference

  Oral presentation


• マリアナ背弧拡大系の地球物理学的研究

  島 伸和, 山崎 俊嗣

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  [Invited]

  Invited oral presentation


• MMR法の磁場の3次元フォワード計算（その3）‐3次元フォワード計算から海底熱水循環系の3次元比抵抗構造を推定する‐

  多田 訓子, 木戸 元之, 島 伸和

  日本地球惑星科学連合2006年大会, May 2006, Japanese, 日本地球惑星科学連合, 幕張, Domestic conference

  Oral presentation


• MMR 法の磁場の 3 次元フォワード計算(その 3)‐3 次元フォワー ド計算から海底熱水循環系の 3 次元比抵抗構造を推定する‐

  多田 訓子, 木戸 元之, SEAMA NOBUKAZU

  日本地球 惑星科学連合 2006 年大会, May 2006, Japanese, 日本, Domestic conference

  Oral presentation


• 海底地形効果の補正についての検証

  松野 哲男, 島 伸和, 馬場 聖至

  ＣＡ研究会, Dec. 2004, Japanese, 未記入, 東京, Domestic conference

  Others


• メタンハイドレート検出を目指した海底電気探査装置の開発

  後藤 忠徳, 渡辺 俊樹, 三ヶ田 均, 真田 佳典, 島 伸和

  ＣＡ研究会, Dec. 2004, Japanese, 未記入, 東京, Domestic conference

  Others


• Magnetometric Resisticity Methodを用いた海底熱水循環系の電気伝導度構造の推定

  多田 訓子, 島 伸和, 松野 哲男, 岩本 久則, 北田 数也, 木戸 元之, 後藤 忠徳, 下泉 政志

  ＣＡ研究会, Dec. 2004, Japanese, 未記入, 東京, Domestic conference

  Others


• Hydrothermal circulation system in the central Mariana illustrated by Magnetometoric Resistivity experiments

  TADA, N, SEAMA, Nobukazu, GOTO, T, KIDO, M

  2004 American Geophysical Union Fall Meeting, Dec. 2004, English, 未記入, San Francisco, USA, International conference

  Poster presentation


• Geophysical features of hydrothermal system in Suiyo Seamount, Izu-Ogasawara Arc, Western Pacific

  SEAMA, Nobukazu, NISHIZAWA, A, KAWADA, Y

  2004 American Geophysical Union Fall Meeting, Dec. 2004, English, 未記入, San Francisco, USA, International conference

  Others


• 自律型海中ロボットｒ2Ｄ4の深海地磁気三成分観測

  田村 千織, 野田 裕美子, 島 伸和, 玉木 賢策, 藤本 博巳, 浦 環

  物理探査学会第111回学術講演会, Sep. 2004, Japanese, 物理探査学会, 岩手, Domestic conference

  Others


• メタンハイドレード検出を目指した海底電気探査装置の開発

  後藤 忠徳, 三ヶ田 均, 渡辺 俊樹, 真田 佳典, 島 伸和

  物理探査学会第111回学術講演会, Sep. 2004, Japanese, 物理探査学会, 岩手, Domestic conference

  Others


• 水曜海山の地球物理学的構造と海底熱水循環系

  島 伸和, 西澤 あずさ, 木下 正高, 西村 清和, 川田 佳史

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Others


• 初期コンドワナ分裂時の西エンダビー海盆の海底拡大

  野木 義史, 西 久美子, 島 伸和, 福田 洋一

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会2, 幕張, Domestic conference

  Poster presentation


• 重力異常から見たマリアナトラフ背弧拡大

  北田 数也, 山崎 俊嗣, 島 伸和, 岩本 久則, 松野 哲男, 富士原 敏也, 沖野 郷子, 野木 義史, 末広 潔

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Poster presentation


• 海底熱水循環系を電気伝導度で探る

  多田 訓子, 島 伸和, 松野 哲男, 岩本 久則, 北田 数也, 木戸 元之, 後藤 忠徳, 下泉 政志

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Others


• マリアナ沈み込み帯上部マントルの電気伝導度構造（2） 次期高分解能観測のための数値シミュレーション

  馬場 聖至, SCHWALENBERG Katrin, 島 伸和, EVANS Rob L

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Poster presentation


• マリアナ沈み込み帯上部マントルの電気伝導度構造（1） 2001－2002年海底MT観測の成果

  馬場 聖至, 後藤 忠徳, 島 伸和, 市來 雅啓, 歌田 久司, 末広 潔

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Others


• MMR制御電流を入力とした3次元電場・磁場の計算

  木戸 元之, 多田 訓子, 島 伸和

  地球惑星関連学会2004年合同大会, May 2004, Japanese, 地球惑星関連学会, 幕張, Domestic conference

  Poster presentation


• An overview on results of recent Japanese geophysical surveys in the Mariana area

  SEAMA Nobukazu

  Ridge 2000-InterRidge Joint Theoretical Institute, Interactions among Physical, Chemical, Biological, and Geological Processes in Backarc Spreading Systems, May 2004, English, 未記入, Jeju Island, Korea, International conference

  Poster presentation


• かいれい「KR03-13」Magnetometrc Resistivity Methodを用いた電気伝導度構造の推定

  多田 訓子, 島 伸和, 松野 哲男, 岩本 久則, 北田 数也, 木戸 元之, 田中 仁氏, 松浦 由孝, 佐藤 悠介, 上野 珠民, 後藤 忠徳, 下泉 政志

  アーキアン・パーク計画 平成15年度第2回課題検討会議, Jan. 2004, Japanese, 未記入, 山中湖, Domestic conference

  Poster presentation


• MMR制御電流を入力とした3次元電場・磁場の計算

  木戸 元之, 多田 訓子, 島 伸和

  アーキアン・パーク計画 平成15年度第2回課題検討会議, Jan. 2004, Japanese, 未記入, 山中湖, Domestic conference

  Poster presentation


• 島弧の海底熱水系に特有な構造と性質と地下生物圏への影響

  浦辺 哲郎, 丸山 明彦, 島 伸和, 石橋 純一郎, 丸茂 克美, 木下 正高

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• 中部マリアナ背弧系の電気伝導度構造

  馬場 聖至, 島 伸和, 後藤 忠徳, 市來 雅啓, 笠谷 貴史, 野木 義史, KATRIN Schwalenberg, 岩本 久則, 多田 訓子, 松野 哲男, 末広 潔, 歌田 久司, 「よこすか」Y, 航海乗船者, いれい航海研究者

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• 中部マリアナトラフ拡大過程の復元

  岩本 久則, 山本 路子, 島 伸和, 野木 義史, 後藤 忠徳, 北田 数也, 松野 哲雄, 富士原 敏也, 末広 潔, 山崎 俊嗣

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• 瀬戸内海海底重力測定

  上嶋 正人, 石原 丈実, 小泉 金一郎, 島 伸和, 押田 淳, 藤本 博巳, 金沢 俊彦

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• マリアナトラフの重力異常

  北田 数也, 島 伸和, 山崎 俊嗣, 富士原 敏也, 若林 直樹, 中瀬 香織, 沖野 郷子, 野木 義史, 末広 潔

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• コントロールソースを用いた海底電磁気探査装置の開発（2）

  島 伸和, 後藤 忠徳, 多田 訓子, 岩本 久則, 北田 数也, 松野 哲男, 野木 義史, 山口 覚, 下泉 政志, 松田 滋夫, 村上 英幸, 川上 太一, いれい航海研究者

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation


• MMR法を道板中部マリアナトラフの拡大軸直下の電気伝導度構造の研究

  多田 訓子, 島 伸和, 後藤 忠徳, 岩本 久則, 北田 数也, 松野 哲男, 野木 義史, 笠谷 貴史, 市來 雅啓, 吉田 茂生, 川田 佳史, いれい航海研究者

  地球惑星科学関連学会2003年合同大会, May 2003, Japanese, 地球惑星科学合同大会運営機構, 幕張, Domestic conference

  Oral presentation

• 日本地球惑星科学連合


• American Geophysical Union


• 日本地震学会


• 地球電磁気・地球惑星圏学会

• 巨大カルデラ噴火を導いたマグマ供給系の現状把握

  島 伸和, 山本 揚二朗, 松野 哲男, 伊藤 亜妃

  日本学術振興会, 科学研究費助成事業, 基盤研究(A), 神戸大学, Apr. 2020 - Mar. 2024

  研究目的を達成するために、鹿児島市の南約100kmの海域に位置する「鬼界海底カルデラ火山」を対象として、この巨大カルデラ火山のマグマ供給系全体の地球物理学的なイメージングを実施する。これにより、鬼界カルデラ直下に存在すると考えられる特徴的な構造の位置や大きさ等を把握する。 本年度は、巨大カルデラ火山のマグマ供給系全体のイメージングのために、現在実施している海底および陸上での地震観測と海底電磁気観測を継続するとともに、一部の観測機器の回収を行うことで観測データを取得した。まず、昨年度の3月に神戸大学の練習船「深江丸」の航海により回収した海底電位差磁力計（OBEM）を再設置するための準備として、必要な消耗品を購入と整備を行った。そして、7-8月に実施されたJAMSTECの海底広域研究船「かいめい」のKM21-05航海により、昨年度設置した短周期海底地震計（SPOBS）と海底磁力計（OBM）の回収およびOBEMの再設置を行った。また、10月に実施した練習船「深江丸」の航海においても、SPOBSの回収を行った。さらに、昨年度に広帯域地震計を設置した臨時陸上観測点で、観測機器の点検と観測データの回収と、一部の地点で磁力計の設置も行い、観測はそのまま継続している。 得られた観測データの解析を順次進めている。まず、OBEMにより得られた海底電磁場変動データからMTレスポンスを求め、1次元の比抵抗構造を推定した。一方で、海底で得られたMTレスポンス等をもちいて3次元比抵抗構造を推定するためのインバージョン手法の開発を進めた。また、SPOBSおよび陸上観測で得られた地震波形データから、観測網の直下で発生していた地震のデータを取り出し、走時を用いたローカルトモグラフィ解析の準備を進めた。 翌年度に計画している海底観測機器の回収のために航海申請等を行い、この航海に必要な準備を始めた。


• Development of AI for autonomous ship handling to accelerate ocean-bottom exploration, and its demonstration at actual sea

  橋本 博公, 青木 尊之, 松田 秋彦, 島 伸和

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), Apr. 2020 - Mar. 2023

  本研究では，気象海象が複雑に変化する状況下において，海洋底探査に課せられた高度ミッションを達成するための自律操船AIの開発を行っている。今年度の研究実績の概要は以下の通り。 ①深層強化学習により，海洋調査に用いられる測線トラッキング用の自律操船AIの開発を行った。風，波，潮流が混在する中での直線航路のトラッキングに加えて，測線の終了点から次の測線の始点を直線で繋いだ不連続な航路に対しても最小の偏差で追従可能とするために，測線と自船の位置関係をニューラルネットワークへの入力としている。開発したAIの評価のため，水産研究・教育機構の漁業調査船「たか丸」を使用して，AIの舵角指示をディスプレイに表示し，船員（人間）がそれに応じて操舵する半自動操船システムを構築した。そのうえで，複数回の実船実験を通じて，船内情報収集システムの検証やAIのトラッキング精度について検証を行った。本システムはAIの判断を効果的に伝達するインターフェースが重要であるため，複数の船員に操船してもらい改善すべき事項についてフィードバックコメントを収集した。 ②風，波，潮流という外乱作用下での定点保持操船の自動化のために、舵角だけでなく，CPPのプロペラ翼角とバウスラスターのオンオフを行動に含めたプロトタイプのAIを開発し，「たか丸」で検証実験を実施した。 ③水産技術研究所の海洋工学総合実験棟において，次年度に実施を予定しているAIによる定点保持操船の模型実験に向けた予備的実験を行った。


• 深海における地磁気異常が明らかにする古地磁気変動

  島 伸和

  科学研究費補助金／基盤研究(B), Apr. 2015 - Mar. 2019, Principal investigator

  Competitive research funding


• 海底拡大系から探る上部マントルの不均質構造

  島 伸和

  科学研究費補助金／基盤研究(B), Apr. 2015 - Mar. 2019, Principal investigator

  Competitive research funding


• Geological and geophysical background of subseafloor hydrothermal systems "TAIGA"

  OKINO KYOKO, SEAMA Nobukazu, SHINOHARA Masanao, SATO Hiroshi, UMINO Susumu, NOGI Yoshifumi, ASADA Miho, ABE Natsue, SATO Toshinori, MORISHITA Tomoaki, NAKAMURA Kentaro, FUJIWARA Toshiya, MOCHIZUKI Nobutatsu, YAMAMOTO Junji, TSUJI Takeshi, YOSHIKAWA Shuro

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area), The University of Tokyo, Apr. 2008 - Mar. 2014

  The integrated geological and geophysical field surveys were conducted on the hypothesis that the diversity of subsealoor hydrothermal circulation (TAIGA: Great River) is controlled by tectonic and geological setting beneath and around the hydrothermal fields. The series of AUV and submersible dives and geophysical explorations showed that the sulfur-rich hydrothermal sites in the southern Mariana backarc spreading center are controlled mainly by the waxing and waning of magmatic activity. In contrast, the results of geological, geophysical surveys and rock geochemistry revealed that the hydrogen-rich Kairei hydrothermal field at the southernmost Central Indian Ridge is constrained by both axial basaltic magmatism and detachment faulting that exhume ultramafic rocks on a shallow subsurface.


• Melt region structures beneath back-arc basin spreading centers

  SEAMA Nobukazu, NOGI Yoshifumi, NAKAKUKI Tomoeki, TAKEI Yasuko, MATSUNO Tetsuo

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), Kobe University, 2009 - 2011, Principal investigator

  Investigations on melt region structures beneath spreading axes are a key to understand back-arc spreading system. We developed a compact ocean bottom magnetometer(OBM), which was designed to be attached to US ocean bottom seismograph(OBS); that became first ocean bottom seismograph and magnetometer(OBSM) in the world achieved by an international cooperation. We carried out one year ocean bottom observation near the Eastern Lau spreading axis using the instruments. Marine magnetotelluric analysis using ocean bottom data allows us to image the resistivity structures of the upper mantle beneath the spreading axis, which were compared to identify differences in melt region structures and to understand the cause of the differences.

  Competitive research funding


• Does mantle geochemistry control the mid-ocean ridge process?-Southwest Indian Ridge expedition

  OKINO Kyoko, SHIMA Nobukazu, SATO Toshinori, UMINO Susumu, NOGI Yoshifumi, FUJIWARA Toshiya, NAKAMURA Yasuyuki, YAMAMOTO Junji, SATO Hiroshi, KUMAGAI Hidenori, SUZUKI Katsuhiko, ABE Natsue, HARADA Yasushi, ASADA Miho, SHINOHARA Masanao, NAKAMURA Kentaro, SENDA Ryoko, SATO Taichi, KITAMURA Takayuki, MIZUNO Mariko, MIZUMA Keiko

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), The University of Tokyo, 2007 - 2009

  The geophysical and geochemical survey was done along the ultraslow spreading Southwest Indian Ridge 31-41°E. Geophysical data shows the spatial and temporal variation of the melt supply in the area, which corresponds to the variation of mid-ocean ridge process such as spreading asymmetry and obliquity. The result of rock analysis also suggests the existence of small-scale heterogeneity of mantel geochemistry and/or temperature. The upper mantle structure and microseismicity are also revealed.


• 電気伝導度と地震波速度による沈み込み帯の構造に関する研究

  島 伸和

  日本学術振興会, 科学研究費補助金／特定領域研究, 特定領域研究, 神戸大学, 2005 - 2006, Principal investigator

  前年度に調べた電気伝導度構造、地震波速度構造の2つの違った構造と沈み込み帯の上部マントルでの物性量の関係から、それぞれの構造と物性量の関係が比較的明らかな異方性に注目した.地震学的観測データによるS波速度の異方性は、各観測点におけるS波スプリッティングで生じた、速いS波の振動方向と、速いS波と遅いS波の時間差によって調べられるため、異方性が生じている深度の情報が含まれていない.一方、電磁気的観測データでは、異方性の方向とその程度の分解能は低いが、深度に関する情報が含まれている.このため、S波スプリッティングの結果を使い、上部マントル物質であるオリビンの異方性に関する物性から条件をつけて、電磁気的観測データを解析する手法の検討を行った.さらに、これによる電気伝導度異方性構造を推定する解析手法の開発を現在も進めている. 研究協力者である大学院生(岩本)を同じく研究協力者であるワシントン大学のDouglas A.Wiens教授に派遣して地震学的観測データの解析を行った.マリアナ背弧海盆拡大軸付近の海底地震計による観測データを解析することにより、この付近で起こる微少な地震の震源分布を明らかにした.また、Wiens教授のグループの大学院生であるS.H.Pozgayが、同じ海底地震計による地震観測データを解析することにより、各観測点におけるS波スプリッティングを調べ、速いS波の振動方向と速いS波と遅いS波の時間差の空間分布を明らかにしつつあった.この結果を、開発中の電気伝導度異方性構造を推定する方法に、どのように適用するかにっいての検討も行った.現実のデータにおいては、S波の振動方向や時間差には、空間的なばらつきがあるため、直接に組み込むことができず、単純化する必要があることがわかった.

  Competitive research funding


• Marine magnetotelluric experiment across the central Mariana subduction-arc-back arc system

  SEAMA Nobukazu, UTADA Hisashi, GOTO Tada-nori, BABA Kiyoshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 2005 - 2006, Principal investigator

  We carried out a marine magnetotelluric transect across the central Mariana subduction-arc-back arc system using ocean bottom electro-magnetometers (OBEMs), ocean bottom electrometers (OBEs), and ocean bottom magnetometers (OBMs) to provide the electrical conductivity structure of the Mariana island-arc system extending from the Pacific ocean to the West Mariana Ridge (remnant arc) through the Marina Trough. Deployments of 33 OBEMs, 7 OBMs, and 7 OBEs were made at 40 sites across the central Mariana subduction-arc-back arc system during KR05-17 cruise. Observations using the instruments were made from December 2005 up to the recovery in September 2006. We successfully recovered 28 OBEMs, 7 OBMs, and 6 OBEs at 35 sites during KR06-12 cruise. We are still analyzing these data to estimate the upper mantle electrical conductivity structure, because the observation was delayed. But, these data will provide a comprehensive image of the conductivity structure for the central Mariana subduction-arc-back arc system, because the observation sites are so dense. We analyzed previous 9 OBEM data obtained from the same area. The resulting electrical resistivity structure shows an increase in conductivity at depths of about 70 km beneath the Mariana Trough and anisotropy at deeper depth. The low conductivity structure near Mariana Trough spreading axis implies that the onset of melting in the Mariana Trough back-arc basin is deeper than that of the typical MORB source region. Consideration of the effect of seafloor topography on ocean bottom magnetotelluric data is needed to estimate a reliable conductivity structure. We evaluated three different correction equations to correct the effect of seafloor topography with forward modeling, and we indicate the most an appropriate correction method based on a series of synthetic tests.

  Competitive research funding


• Exploration of sub-seafloor methanehydrate using artificial current source ocean-bottom electromagnetic method and its reservoir estimation

  WATANABE Toshiki, SHIMA Nobukazu, MIKADA Hitoshi, SANADA Yoshinori, GOTO Tadanori

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Nagoya University, 2004 - 2006

  1. A deep-towed electrical sounding system was developed for shallow ocean-bottom conductivity survey, especially for precise determination of the upper limit of hydrate layers. A sensitivity analysis was done in term of the parameters such as the depth, thickness and concentration of the hydrate layer using a electrical-field response modeling code. Optimum design of the observation system was investigated. 2. Improvement of the artificial current source and the Ocean-Bottom ElectroMagnetic equipment (OBEM) was done in Kobe University. JAMSTEC developed smaller-size OBEMs. 3. EM modeling and inversion codes were developed. Discontinuity in the conductivity structure was introduced in the 2-D inversion code, enabling to image sharp layer structures and faults. A 3-D magnetometric modeling code was developed to calculate anomalous magnetic field caused by any 3-D resistivity structure. 4. In the first cruise (Off Sado, August 2005), the newly developed deep-towed electrical sounding system was tested at the depth of 1000 meters below sea-surface and successfully obtained electrical potential data. The electrical resistivity structure from 0 to about 100 meters below sea-floor was analyzed. It was proved that the resistivity structure was consistent to the visual inspection of the sea floor. The distribution of the hydrate was in columnar shape and was first imaged. MMR method using the artificial current source and the OBEMs revealed a low amplitude anomaly of magnetic field in the west of the survey area, suggesting the localized existence of the resistive hydrate in the area. In the second cruise (Off Tokai, February 2006), the operation of the deep-towed electrical system was again in success. The resistivity structure from 0 to about 100 meters below sea-floor was in good agreement with the result of the resistivity logging in the test drilling done in 1999. The two field test proved the reliability and effectiveness of the developed deep-towed electrical sounding system.


• 惑星系の起源と進化

  向井 正

  2006

  Competitive research funding


• Integrated Research on the Mid-oceanic Ridge by Internationally Co-operated Expeditions

  TAMAKI Kensaku, COFFIN Millard, GAMO Tosinori, OKINO Kyoko, ISHIBASHI Junichiro, SEAMA Nobukazu

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), The University of Tokyo, 2002 - 2005

  This project promoted InterRidge Japan as a part of InterRidge International Project with the financial supports for the payment of member's fee of InterRidge (20,000-25,000 US$ annually), travels of Japanese ridge scientists for participating domestic and international mid-oceanic ridge research cruises and InterRidge meetings such as an InterRidge steering committee, InterRidge Symposiums, Workshops, and Theoretical Institutes, and for inviting foreign ridge research scientists. By these supports Japan made a principal contribution to the InterRidge (current number of the member countries is 29) as one of five principal member countries with UK, US, France, and Germany. Two members of this projects are appointed as members of the InterRidge Steering Committee. During four years, 14 mid-oceanic research cruises were conducted with the partial financial supports by this project. The research fields cover marine geology, marine geophysics, water geochemistry, marine biology, and ocean technology. Japan specially contributed in the fields of hydrothermal geochemistry, marine microbiology, and ocean technology. AUV (Autonomous Underwater Vehicle) expedition with three-component magnetometer installed demonstrated the demagnetization of the crust according to the extent of hydrothermal activity at the Mariana Trough in the Western Pacific. Regional water circulation in the oceanic crusts around the mid-oceanic ridge was evidenced by IODP Juan de Fuca Ridge drilling for which this project made partial financial support. The cooperated expedition research at the Southwestern Indian Ridge found wide exposures of mantle rocks on the sea floor which suggest a fundamental mechanism of ultra-slow spreading system with very low magmatism. In 2006 diving research cruises were conducted at the hydrothermal area at the Central Indian Ridge and we succeeded to obtain valuable samples of microbiology and hydrothermal mineralization which analyses are currently ongoing.


• 惑星系の起源と進化

  向井 正

  2005

  Competitive research funding


• Conductivity structure around seismogenic layer beneath the Chugoku and Shikoku districts

  YAMAGUCHI Satoru, OSHIMAN Naoto, SHIOZAKI Ichiro, MURAKAMI Hideki, SHIMA Nobukazu, UYESHIMA Makoto

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 2001 - 2002

  We delineated the Philippine Sea plate beneath the South-western Japan arc using the electro-magnetic method in this study. The Network-MT method is one of the magnetotelluric methods and it is suitable for surveying a conductivity structure beneath a wide area and to a deep portion. We applied the method in Chugoku and Shikoku district to reveal a subsurface structure beneath the South-west Japan arc. We focused on the where and how does the Philippine Sea Plate exist. The first reason is that a location of The Philippine Sea plate is most important factor to controlled occurrences of earthquakes, because the cold and rigid plate makes large influence on a thermal state and/or a distribution of seismic-wave velocity. Second reason is that it is hard to decide a location of the plate using only seismic methods. The precise 2-dimensional conductivity model was established. This model is characterized by following points. 1) North dipping resistive layer (> 500Ω・m) exists beneath both Chugoku and Shikoku districts. The upper depth of the resistive layer is 20km, 30km beneath the southern and northern part of the Shikoku district, and 40km, 60km beneath the southern and northern part of the Chugoku district, respectively. 2) Conductive layer (~100Ω・m) exists beneath the north dipping resistive layer. 3) Highly conductive layer is found at 40km-depth beneath the northern most part of the Chugoku district. We interpreted the north dipping resistive layer is the Philippine Sea plate.


• Spreading process of the Mariana Trough

  SEAMA Nobukazu, ISEZAKI Nobuhiro, HYODO Masayuki, YAMAZAKI Toshitsugu

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (B), Kobe University, 2000 - 2002

  The Mariana Trough is a typical intra-oceanic back-arc basin that shows a variety of features. We have compiled extensive surface geophysical data (bathymetry, magnetic and gravity) of the Mariana Trough, which were collected during several Japanese cruises over the last few years. Topographic features and the mantle Bouguer anomaly (MBA) reveal distinct differences between regions. The north of 22N shows extremely low MBA indicating an incipient rifting. The central region between 21N and 14N shows characteristic slow-spreading features; existence of median valley neovolcanic zone and "Bull's eyes" MBA along the axes. The south of 14N shows an EPR type axial relief morphology and lower MBA than that in the central. Tectonic evolution can be inferred from the direction of spreading fabric, the trace of non-transform offsets, and by crustal ages identified by vector geomagnetic anomaly field. The crustal ages indicate that the seafloor spreading started at 4Ma, 6Ma and 3Ma at the northern end, the central, and the southern end, respectively. The spreading rates are generally slow (~20 mm/yr) in the northern and central areas, while they are fast (~35 mm/yr) in the south. Spreading axis directions have gradually changed by 15 degrees clockwise with age in the north of 17.5N, while they occurred at 3.5-3.0Ma from N35W to N5W just south of 17.5N. On the other hand, they are relatively constant in the southern end. We have developed a new type of ocean bottom electro-magnetometer (OBEM), which is small and easy to handle with Filloux-type electrodes. Preliminary results of an OBEM observation for one year in the Mariana region suggest that very conductive zone (about 70km in depth) below the Marianas island arc and low conductivity zone with thickness of a few ten km beneath the Mariana Trough.


• International Cooperative Research on the mid-Oceanic Ridges-Earth Environmental Dynamics and Mid-Oceanic Ridge

  TAMAKI Kensaku, SHIMA Nobukazu, ISHIBASHI Jun-ichiro, FUJIMOTO Hiromi, ISEZAKI Nobuhiro, NAGANUMA Takeshi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for Scientific Research (A), The University of Tokyo, 1999 - 2001

  This budget is the Japanese counterpart of the InterRidge program. The budget is used for travels of the Japanese scientists and transportation of the instruments for research cruises, travels of the Japanese scientists to participate InterRidge meetings, and travels for invited foreign scientists. 1. Results of mid-oceanic ridge research cruises The Japanese scientist members of this project participated 12 research cruises in the Western Pacific, Indian Ocean, Northern Atlantic, and the back-arc basins. The research fields cover tectonics, geochemistry, seismology, petrology, biology and microbiology. Major achievements are the discover of the first active vent site in the Indian Ocean, identification of hotspot-ridge interaction at the Aden rift system in the Indian Ocean., and mapping of segment configuration of the Knipovich Ridge in the Arctic Sea. 2. Promotion of InterRidge program The Japanese scientist members of this project intensively participated steering committees, workshops, symposiums, and theoretical institutes organized by InterRidge. As the activity of the Japanese scientists for InterRidge project, the steering committee approved to move the InterRidge Office to Japan for 4 years from 2000. The Office is now at the Ocean Research Institute, and K. Tamaki serves as a chairman. 3. Invitation of foreign scientists We invited a number of scientists from Russia, England, Yemen, and France to do the summary discussion of the research cruises and to devise future program plan. Two new proposals for the mid-oceanic ridge of the Atlantic ocean were submitted through the discussion with the invited foreign scientists.


• Structure and Tectonics of Japan Sea and Sikhote Alin and their relation to Japan Arc

  ISEZAKI Nobuhiro, KULINICH Ruslan, SEAMA Nobukazu, SHINOHARA Masano, HIROI Yosikuni, ITO Tanio

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for international Scientific Research, Chiba University, 1996 - 1998

  l.Research in the Japan Basin During this cooperative research, the marine investigations had been carried out by R/V Prof.Gagarinsky of POI on the tracks of 5 mile interval in the whole area of Japan Basin in the Russian EEZ.. a.Seismic investigation : OBSs of Chiba University and the single air-gun of P01 were used for the seismic research in the Japan Basin resulting in that the thickness of crust in the central part of the Japan Basin is 8-9km including 1.5km thick sediments and increasing towards east. The feature of crust is not completely identical with the typical oceanic one.The crust in the eastern part of the Basin is oceanic, then the central part of the Basin has the different developing mode from the east part, namely sea floor spreading development. b.Magnetic investigation : A proton precession magnetometer of POI and a STCM(Shipboard Three Component Magnetomete) of Chiba Univ. were used for the magnetic study of the Basin resulting in that there are clear magnetic anomaly lineations in the eastern part of the Basin and not so clearly in the cental part. This is coincident with the seismic investigation mentioned above. c.Gravity investigation : A shipboard gravimeter of POI was used. The structures of the crust obtained from gravity anomalies change from the oceanic to the continental from east to west. 2.Research in the Sikhote Alin (Geological Research) The geological investigation was done to reconstruct the original position of Japanese islands before opening of the Japan Sea using the geological data in the SikhoteAlin especially of Tercialy time. The geological continuation between the Japanese islands and the Sikhote Alin in the Tercially time was revealed taking other data, that are, tobography of the Basin floor and deformation of the Japanese Island Arc into account.


• International Cooperative Research on the mid-Oceanic Ridges

  TAMAKI Kensaku, ISEZAKI Nobuhiro, MEVEL Catherrine, NAKANISHI Masao, OOTA Suguru, FUJIMOT Hiromi

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for international Scientific Research, the University of Tokyo, 1996 - 1998

  This program corresponds to the InterRidge program, an international initiative of mid-oceanic ridge studies. The funds of this program are mainly used for travels of ridge researchers in Japan for participating cruises, attending workshops, program planning meetings, and society meetings. The other part of usage is transportation of instruments for the research cruises. The research cruises that the researchers of this program participated cover the global ridge system including the Juan de Fuca Ridge, the East Pacific Rise, the Mid-Atlantic Ridge, the Southwestern Indian Ridge, the Central Indian Ridge, and the western Pacific back-arc basins ridges. The major achievements were done in the studies in the Southwestern Ridge. Five research cruises were executed at the Southwestern Indian Ridge during this program. Multinarrow bathymetric survey, deep-tow sidescan sonnar survey, gravity and magnetic measurements, ocean bottom seismometer measurements, and bottom rock sampling were done. The compilation of these data sets clearly shows the unique segmentation pattern of this ridge, the ultraslow spreading system with striking heterogeneity of crustal structure and intensively focused magmatism.


• Electromagnetic and Tomographic Research of Melt below EPR

  HAMANO Yozo, GOTO Tadanori, YAMANO Makoto, UTADA Hisashi, KASAHARA Junzo, TOH Hiroaki

  Japan Society for the Promotion of Science, Grants-in-Aid for Scientific Research, Grant-in-Aid for international Scientific Research, The University of Tokyo, 1995 - 1997

  As for geophysical measurements around the East Pacific Rise (EPR four Ocean Bottom Electro Magnetometers (OBEMs) were successfully retrieved during a research cruise from the end of May/'97 through the beginning of July/'97 by R/V Melville of Scripps Institution of Oceangraphy, US,to yield electromagnetic (EM) time series at the seafloor for more than one year. The OBEMs have been installed at 17ﾟS of EPR during a previous research cruise from the middle of May/'96 through the beginning of July/'96, which was also an international cruise coordinated by Mantle ELectromagnetic and Tomography (MELT) Project. The EM data from these seafloor units are now being analyzed together with those simultaneously collected by US and Australian groups. The goal of the analyzes and subsequent modellings/inversions is reveal the EM structure of melt bodies just below the super spreading center. Specifically, this research aims at quantifying the geometry, melt fraction and connectedness of the melt bodies by a joint observation of seismics and magnetotellurics at the seafloor. In terms of study of the very old oceanic crust in Archaen, rock sampling was conducted in South Africa and Zimbabwe this year. The samples collected are either igneous or sedimentary rocks as old as 2,500 to 3,500 Ma. These samples are in the course of petrological, geological and paleomagnetic analyzes to yield estimates of the tectonic activity at the seafloor and Earth's geomagnetic field in Archaen, which will be combined with the results from the samples collected in Australia ('95) and in Canada ('96) to give reconstruction of a worldwide view of the Earth in Archaen.


• 高感度マグネットテルリック法で中央海嶺下溶融体の底を見る

  藤 浩明, 島 伸和, 歌田 久司

  日本学術振興会, 科学研究費助成事業, 一般研究(B), 東京大学, 1995 - 1995

  「海底電磁気データから中央海嶺下溶融体の深部構造を決定する方法を確立」する事を主眼に本年度の研究を進めた。本研究では、(1)磁場データの感度向上、(2)長周期(具体的には潮汐周期帯)信号の開拓、(3)電磁場のmigrationに基づいた構造解析法(イメージング法)の導入、の3点からこの目的を達成する事を試みた。(1)により、電場に比べ明らかに感度が足りない事が分かって来た磁場データを高感度で採取する事で厚い海水のスクリーニングを受けても浅部構造を精密に決める事が可能になる。(2)では、新しい時系列解析法を開発し海洋潮汐により海洋中でキネマティックに誘導される電磁場を信号源として活用する事により、上部マントルの持つコンダクタンスの上限値が制約条件として得られ、(1)で得られた浅部構造と組み合わせる事によって、中央海嶺下部に存在する溶融体の「底」が見えて来る。また(3)では、時間領域及び周波数領域における電磁場のmigrationに基づいたイメージング法を新たに導入し、これを従来の電気伝導度構造解析と組み合わせる事により、海底電磁気データの形状決定に対する分解能の向上につながる。 (1)の測器改良では、高感度3成分磁場センサーを導入する事により磁場感度の向上を実現でき、改良した測器を伊豆小笠原弧をテストフィールドとした海域実験に投入し高感度磁場データを取得する事が出来た。(2)の海洋潮汐を信号源とする新しい解析法、及び、(3)の電磁場のmigrationを利用した新しい構造解析法、についても必要なソフトウェア群は一応の完成をみた。但し、海域実験の時期が本年度後半にずれ込んだ為、観測データの一部はまだ解析の途上にあり実測データに基づく新しい解析手法の有効を検証するまでには至っていない。しかしながら、ほぼ所期の目的を達成する事が出来たと考えられる。