A5060895515- Geophysical and Geoelectrical Methods
- Geological and Geophysical Studies
- Geophysical Methods and Applications
- Seismic Waves and Analysis
- Methane Hydrates and Related Phenomena
- Earthquake Detection and Analysis
- earthquake and tectonic studies
- Geological and Geochemical Analysis
- Geology and Paleoclimatology Research
- Geomagnetism and Paleomagnetism Studies
- Seismic Imaging and Inversion Techniques
- Underwater Acoustics Research
- Underwater Vehicles and Communication Systems
- Paleontology and Stratigraphy of Fossils
- Modular Robots and Swarm Intelligence
- Non-Destructive Testing Techniques
- Neural Networks and Applications
- Fractal and DNA sequence analysis
- Tunneling and Rock Mechanics
- Blind Source Separation Techniques
- Geological Studies and Exploration
- Hydrocarbon exploration and reservoir analysis
- Mineral Processing and Grinding
- Distributed Control Multi-Agent Systems
- Drilling and Well Engineering
Nippon Seiki (Japan)
2019-2021
Japan Agency for Marine-Earth Science and Technology
2017-2020
Kobe University
2007-2009
Abstract Although seafloor massive sulfide (SMS) deposits are crucially important metal resources that contain high‐grade metals such as copper, lead, and zinc, their internal structures generation mechanisms remain unclear. This study obtained detailed near‐seafloor images of electrical resistivity in a hydrothermal field off Okinawa, southwestern Japan, using deep‐towed marine tomography. The image clarified semi‐layered structure, interpreted SMS exposed on the seafloor, another...
Lower to Middle Cretaceous red sandstones were sampled at four localities in the Lanpin-Simao fold belt of Shan-Thai Block describe its regional deformational features. Most samples revealed a characteristic remanent magnetization with unblocking temperatures around 680 °C. Primary natures are ascertained through positive test. A tilt-corrected formation-mean direction for Jingdong (24.5°N, 100.8°E) locality, which is located distance 25 km from Ailaoshan–Red River Fault, northerly...
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...
<title>Abstract</title> Megathrust and slow earthquakes are known to occur in the area off Kumano, along eastern part of Nankai Trough, Japan. Pore fluids fault surface play an important role earthquake occurrence, but detailed fluid distribution remains unknown. In this study, based on seafloor electromagnetic field observations, we estimated three-dimensional resistivity structure, which reflects off-Kumano. The optimal model showed a low layer at shallow depths below did not indicate any...
SUMMARY In order to describe features of tectonic deformation in the Indochina Peninsula, Early Jurassic Cretaceous red sandstones were sampled at three localities Shan-Thai and blocks. Stepwise thermal treatment most samples revealed presence characteristic remanent magnetization, which is generally unblocked by 680 °C. This component from Phong Saly (21.6°N, 101.9°E) Borikhanxay (18.5°N, 103.8°E) yield positive fold tests with Late Jurassic–Early directions Dec/Inc = 28.8°/32.1° (ks=...
Abstract Deep‐sea chemosynthetic ecosystems are ‘oases’ of life powered by reducing geofluids, which serpentinite‐hosted seeps among the least studied. South Chamorro Seamount, a serpentine mud volcano on Mariana Arc, has been known to host chemosynthesis‐based assemblages since 1996, but no detailed information fauna was published. Here, we revisited characterise its biodiversity. We located two regions communities dominated bathymodioline mussels, vesicomyid clams, and chaetopterid...
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...
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。
内閣府主導の戦略的イノベーション創造プログラム(SIP)の一つとして,次世代海洋資源調査技術「海のジパング計画」が2014年にスタートした。このプログラムのもと,概査から精査に至る調査手法に関して「海底熱水鉱床調査技術プロトコル」が策定され,このプロトコルの概査から準精査までの一部の調査過程を実証するための調査航海を行った。実証航海前に概査として取得したデータをもとに設定した海域において,準精査に相当する調査を行った。まず,船舶装備のMBESによる稠密観測で約10...
A 3D marine controlled-source electromagnetic (CSEM) survey for mapping hydrocarbons uses dozens of ocean-bottom electric (OBE) receivers deployed in a grid pattern and several transmitter towlines. This study considers seafloor massive sulfides (SMS) exploration, the horizontal scale SMS is few kilometers, which small compared with hydrocarbon surveys tens kilometers. If we apply CSEM using receiver deployment on grids to map SMS, high costs will be incurred despite size. We have developed...
The finite element method using an unstructured tetrahedral mesh is one of the most effective methods for 3-D modelling marine magnetotelluric data that are strongly affected by bathymetry, because it enables us to incorporate both small-scale and regional-scale bathymetry into a computational with practical number elements. authors applied inversion scheme this type problems first time verified its applicability. Forward calculations two models demonstrated results obtained close reference...
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...
Japan has the sixth largest exclusive economic zone area in world. It is becoming increasingly clear that seabed resources of (EEZ) Japan. They include mineral as well important widely and abundantly distributed energy resources, such methane hydrate. In recent years, autonomous underwater vehicles (AUV), which can obtain data higher definition than survey vessels, are useful even for ocean bottom resources. However, an AUV narrow volumes small.
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...
Abstract Chemosynthetic ecosystems powered by microbial primary production are rare ‘hot spots’ of biological activity in the deep‐sea characterized dense aggregations specially adapted animal species. Among settings where such systems have been found, serpentinite‐hosted seep supported alkaline geofluid particularly understudied with just a few known sites worldwide. Mariana Forearc hosts world's only series active serpentinite mud volcanoes, but communities reported from South Chamorro...
Abstract Lakes of molten sulfur are features sometimes found in seafloor hydrothermal vent systems. Daikoku the northern Mariana Arc is notable for being home to one such inside its summit caldera, “Sulfur Cauldron” discovered 2006. A number oceanographic research cruises since then have revealed significant volcanic activities on Seamount, including an eruption event 2014 leading formation a new basin‐like crater. How this impacted lake Seamount remained unclear. Here, we revisited with...
Abstract Two-dimensional resistivity surveys were carried out along two profiles that laid across earthquake faults initiated by the 2000 Western Tottori earthquake. One profile was located 7 m from a trenching pit, thereby enabling direct comparison of cross-section with geological and, subsequently, precise interpretation structure. Features found to correspond fairly well cross-section. A clear boundary between resistive and conductive zones matches fault survey. Variations in depend...
SMS (Seafloor Massive Sulfide) deposits, including rare and precious metals, have been often found out in the vicinity of hydrothermal active areas: for example Okinawa Trough, Izu-Bonin arc, Azores triple junction mid-Atlantic ridge. Geophysical explorations with electromagnetic (EM) methods are recently carried around deposits Papua New Guinea because known as low resistivity material. The distribution below seafloor can be a good indicator buried deposits. However, structure areas has not...
海底熱水鉱床のような海底地形の起伏が激しい地域において海底下浅部の比抵抗構造を簡便に把握するために,鉛直方向に電極を配置した電気探査装置の開発を行った。本装置の鉛直電極アレイを用いることで鉛直電場の計測による自然電位探査を行うことができる。鉱体の直上において鉛直電場の異常は自然電位の異常と同位相となるため,鉛直電場は海底熱水鉱床と関連する負の自然電位異常域を捉えやすいと考えられる。実海域での観測として,中部沖縄トラフに位置する伊是名海穴の熱水鉱床域で過去に取得された自然電位観測測線上で実施した例を紹介する。観測では複数の鉛直電場の異常域を検出することができた。これらの異常域の空間分布は,これまでの観測で得られている異常域の分布と極めて良い一致を示す。鉛直電極アレイに沿った海底からの距離が異なる6つの電極組み合わせで得られた電場を比較したところ,海底に近い組み合わせほど負の異常の振幅が大きく短波長の空間変動に富み,海底から離れた組み合わせほど振幅が小さく短波長の空間変動が減衰する傾向がみられた。鉛直電場の直接計測は,複雑なデータ処理を必要とせず,鉱体に伴う異常域の検出を簡便に行える方法である。
熱水活動に伴って形成される海底熱水鉱床は，新たな金属資源として注目されている。熱水鉱床は低比抵抗を示すため，海底熱水活動及び海底熱水鉱床の分布調査に海底電気・電磁探査が用いられてきた。しかしながら，これまでに熱水地域で行われた海底電気・電磁探査は簡易的なものに限られており，海底下の広域比抵抗断面の可視化方法は確立されていない。そこで本研究では，深海曳航式電気探査に注目し，熱水地域における深海曳航式電気探査の有効性を評価した。具体的には，有限差分法とOccam's逆解析法を用いた2次元逆解析コードを作成し，数値シミュレーションに基づいて有効性の検討を行った。
深海底の鉱物資源の空間規模把握と成因評価のためには試料の採取および物性計測・化学組成分析が必須である。特に掘削調査により得られる深度方向に連続した試料は,物理探査の有効性評価の観点からも極めて重要である。本研究では海底熱水鉱床の試料情報拡充と潜頭性鉱床に対する自然電位探査の有効性評価を目的とし,潜頭型海底熱水鉱床の胚胎有望地点に対し海底着座型深海用ボーリングシステムによる海底下掘削を実施した。掘削は,熱水兆候と自然電位異常の双方が見られる地域で1点,熱水兆候はあるが自然電位異常のない領域で1点,計2地点で実施された。自然電位異常域で採取されたコアには硫化鉱物の沈殿が確認された一方,自然電位異常の見られない領域で採取されたコアは火山性砕屑物で構成されており,硫化鉱物はほとんど見られなかった。自然電位異常域のコアには詳細な物性計測および化学組成分析が実施された。まず,コア全体に比抵抗測定を実施し,さらにセクションごとに精密なスペクトル誘導分極計測を実施した。また,蛍光X線分析法による元素濃度分析とX線回折分析による鉱物同定も実施し,掘削記載と併せて鉱物分類を行った。その結果,約20...