A5020382054- Methane Hydrates and Related Phenomena
- earthquake and tectonic studies
- Hydrocarbon exploration and reservoir analysis
- Geophysical and Geoelectrical Methods
- Geological and Geochemical Analysis
- Geology and Paleoclimatology Research
- Earthquake Detection and Analysis
- Geological and Geophysical Studies
- Seismic Imaging and Inversion Techniques
- Geological Studies and Exploration
- Seismic Waves and Analysis
- Geophysical Methods and Applications
- High-pressure geophysics and materials
- Seismology and Earthquake Studies
- Landslides and related hazards
- Geological formations and processes
- CO2 Sequestration and Geologic Interactions
- Reservoir Engineering and Simulation Methods
- Geological Modeling and Analysis
- Geochemistry and Geologic Mapping
- Geomagnetism and Paleomagnetism Studies
- Soft Robotics and Applications
- Aeolian processes and effects
- Blind Source Separation Techniques
- Geophysics and Sensor Technology
Japan Agency for Marine-Earth Science and Technology
2010-2024
Tohoku University
2017-2020
National Research Institute for Earth Science and Disaster Resilience
2019
The University of Tokyo
2006-2015
Association for the Development of Earthquake Prediction
2014-2015
Earth Science Institute of the Slovak Academy of Sciences
2014
Nagoya University
2014
We conducted a self-potential survey at an active hydrothermal field, the Izena hole in mid-Okinawa Trough, southern Japan. This field is known to contain Kuroko-type massive sulphide deposits. measured continuously ambient seawater using deep-tow array, which comprises electrode array with 30-m-long elastic rod and stand-alone data acquisition unit. observed negative signals not only above vents visible mounds but also flat seafloor without such structures. Some were detectable >50 m...
Deep-sea massive sulfide deposits formed by hydrothermal fluid circulation are potential metal resources. They can exist not only as mound manifestations on the seafloor (seafloor sulfides) but also embedded anomalies buried beneath (embedded sulfides). The distribution of sulfides is largely unknown, despite their expected high economic value. Recent drilling surveys have revealed a complex model suggesting coexist sulfides. In coexisting case, geophysical methods required to distinguish...
We performed a simultaneous survey of self-potential and plume turbidity using an autonomous underwater vehicle (AUV) above the Sunrise deposit in Myojin Knoll caldera Izu-Ogasawara arc. A 10-m-long electrode rod, on which five electrodes referenced with common were mounted, was connected at tail AUV. The conducted typical speed 2 knots, covering 1500 m × area spacing lines 100 m. With AUV altitude seafloor, negative anomaly few millivolts observed. found to spread 300 is probably...
Phase separation of seawater is an important process controlling the dynamics and chemistry hydrothermal circulation. We numerically investigate circulation in porous media, including phase seawater. Seawater enters crust at seafloor, heated depth, returns to seafloor as fluids. The bottom calculation region are set depths 2500 m 4000 from sea surface, respectively. temperature base 600°C. Under these pressure ranges, supercritical inevitable. Here we focus on steady-state conditions, a...
To explain the origin of a high heat flow anomaly observed within 150 km seaward Japan Trench, we construct thermal model for an oceanic plate prior to subduction that includes effect hydrothermal circulation high-permeability aquifer in its uppermost part. The effects thickening, which is expected occur near zones where bending causes fracturing and faulting plate. Using typical parameter values find thickening mines from underlying basement can account anomaly. ratio supply below as result...
Detecting resistivity and self-potential (SP) anomalies is useful for the exploration of hydrothermal deposits.Using autonomous underwater vehicles (AUVs) can increase survey effectiveness because it allows stable posture control without a towing wire cable from ship.We propose new style geophysical surveys using multiple AUVs electrode marine direct current (MDCR) SP survey.We used two electrical signal transmission their receiver.We successfully conducted MDCR in deposit areas with 20 m...
Anhydrite precipitation strongly affects the circulation of hydrothermal systems by changing permeability structure oceanic crust. For example, a reservoir capped anhydrite precipitates was found beneath caldera floor Suiyo Seamount Izu‐Bonin Arc. We interpret to be due alternating layers lavas and tephras, typical arc volcanos, because layering gives rise mixing high‐temperature fluids with low‐temperature seawater at layer boundaries. thus perform two‐dimensional numerical simulations...
金属鉱床探査などを目的とした自然電位探査は,陸上では従来から行われている。水中においても自然電場探査は行われており,近年では深海における自然電場観測によって海底熱水鉱床を探査する試みも始まっている。海水中では自然電位信号が小さいため,電場データに混入したノイズを除去する必要がある。しかし,複数の並行観測データを足し合わせて平均化する従来の手法(スタッキング)では,並列データに混入したノイズの間に相関が認められる場合,このノイズを除去することは難しい。そこで,海底下からの電場信号とノイズの独立性に着目し,独立成分分析(Independent Component Analysis : ICA)と呼ばれる多成分の混合信号を複数の独立な信号に分離する手法を用いて,ノイズの除去および信号の抽出を試みた。
Heat flow measurements were conducted at four sites in the Nankai accretionary prism southeast of Kii Peninsula, around area where megasplay fault reaches surface, conjunction with long-term monitoring bottom water temperature nearby stations. Analysis obtained data showed that variations seriously affect surface heat areas depths less than about 2,800 m. This effect can reach up to 20% 30% and may have significantly contributed a large scatter values previously measured study area. The...
For the recent national requirements of marine natural resources, Ministry Education, Culture, Sports, Science and Technology (MEXT) started hydrothermal deposit survey tool development program. 'Zipangu in Ocean program' was Strategic Innovation Promotion Program (SIP) managed by cabinet office Japan government for science technological resource around Japan. We planned a multi-purpose electromagnetic instrument with controlled source unit various observation styles. Our transmitter used...
Abstract Anomalous high heat flow is observed within 150 km seaward of the trench axis at Japan Trench offshore Sanriku, where old Pacific Plate (∼135 Ma) subducting. Individual values range between 42 and 114 mW m −2 , with an average ∼70 . These are higher than those expected from seafloor age based on thermal models oceanic plate, i.e., ∼50 The exhibits spatial variations multiple scales: regional (∼100 km) smaller‐scale peaks (∼1 km). We found that hydrothermal mining depth due to...
Environmental impact assessment has become an important issue for deep-sea resource mining. The International Seabed Authority recently developed recommendations guidelines on environmental of mining effects. Several research and development groups have been organized to develop methods the seafloor sub-seafloor under “Zipangu in Ocean program,” a part Cross-ministerial Strategic Innovation Promotion Program managed by Cabinet Office Japanese government. One attempt planned long-term...
Seafloor hydrothermal systems are important in relation to global heat and chemical fluxes as well the distribution of microbial communities within oceanic crust. From a context, low-temperature located far from ridge axes great importance, because their large covered area. Our current understandings seafloor come mainly high-temperature on fast-spreading ridges, which assumed be typical. Recently, observations have been conducted at slow- ultraslow-spreading ridges. In addition, axis...
海底および海底掘削孔内に設置するセンサーの長期安定性評価を行なうことを目的として，長期にわたり安定した温度・圧力を維持できる環境シミュレーターOOVEE（Oil Operated Virtual Environment Equipment）を製作した．OOVEEは，2台の温度安定性±10 mKの恒温槽，安定稼動時の圧力安定性±3 kPaの圧力天秤，容積6.6 Lの圧力容器からなっている．設定できる温度の範囲は－2∼175℃，圧力範囲は1∼100 MPaである．評価試験を行い，22時間にわたり，圧力容器内の圧力を60±0.05 MPa，温度を2±0.008℃に保つことに成功した．圧力の変動は圧力天秤のピストン回転加速によるものであり，2時間程度であればより安定した圧力を連続して供給できる．恒温槽の温度均一性は，深さ10 cm以上の部分で±15 mKである．
Abstract Electric discharge in deep-sea hydrothermal fields leads us to expect the existence of electroactive microbial ecosystems environments. Electrochemical properties such as electric field distribution on seafloor and electrical conductivity rock can be useful indicators searching community natural We performed measurements collected samples by a remotely operative vehicle (ROV) operation. Several spots with strong were detected, which included both active vent areas inactive sulfide...
In this paper, we propose a quantum algorithm for solving the linear advection-diffusion equation by employing new approximate probabilistic imaginary-time evolution (PITE) operator which improves existing PITE. First, effectiveness of proposed PITE is justified theoretical evaluation error. Next, construct explicit circuit realizing Hamiltonian coming from equation, whose gate complexity logarithmic regarding size discretized matrix. Numerical simulations using gate-based emulator 1D/2D...
2001年から2003年にかけて, 水曜海山カルデラ内の熱水地帯での掘削や長期観測を含む集中観測が実施され, 我々は52点で熱流量データを得た。熱水活動が確認された場所では, 概して10W m-2を超える高熱流量が観測された一方, 熱水噴出域からわずか20m以内のところに, 0.04∿0.4W m-2程度の低熱流量域が存在することが確かめられた。また熱水地帯の北東側では, 4W m-2程度の高い熱流量が一様に分布する。さらに孤立型硫化物マウンド脇では, 下に凸や逆転など, 多様な温度-深度分布が得られた。水曜海山の熱水系微細構造は, カルデラ下全体での安定した熱水系を基本として, 熱水上昇域の周囲20m程度での循環系が存在し, さらに個々の熱水噴出の周囲では, 中心に向かって流入速度が徐々に強くなり, ベントから数m以内には熱水溜りと下降流の境界層が存在する。マルチスケールでの熱水系が, 熱流量分布や温度プロファイル等から確認されたのは極めて意義が大きい。
「島弧型」熱水循環系が存在している水曜海山を対象に行なった海上地球物理調査, 深海曳航式地磁気探査, 地震波速度構造探査, 自然地震観測により, 次のような観測事実を明らかにした。1)西峯山体は, 78万年以後のブリュンヌ期に生成したもので, この付近では一番新しい。また, 火口斜面の崩落を起すような活動が山体形成後に起こっている。2)火口西側に磁化を失った領域が, 直径約800mの範囲に広がっている。3)P波速度が2.2kms-1∿4.2km s-1の層が海底下2kmまで存在し, この層では地震はほとんど起こっていない。4)震源は, 火口の直下5km∿10km(海底下3km∿8km)の範囲に集中しており, 中心部分が抜けている煙突状に分布している。このような観測結果を説明するために, 貫入したマグマが冷却するモデルを提案し, その妥当性を数値シミュレーションによって確かめた。数値シミュレーションでは, 貫入したマグマが,...
Recent heat flow surveys in the Japan Trench and Nankai Trough areas delineate prominent anomalies correlated with structure of subducting oceanic crust. On seaward side Trench, anomalously high values are pervasively observed within 150 km trench axis. The broad zone can be attributed to trenchward thickening a permeable layer (aquifer) crust associated fracturing due plate bending. Fluid circulation aquifer efficiently pumps up from underlying unfractured part. Overlapping anomaly, local...