Takashi Ogami

Geological Survey of Japan

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Toshihiko Sugai

The University of Tokyo

Osamu Fujiwara

Geological Survey of Japan

Masaaki Yamaguchi

Japan Atomic Energy Agency

Shintaro Abe

Association for the Development of Earthquake Prediction

Kenjiro Mukaiyama

H. Ohmori

The University of Tokyo

Eiji Sasao

Japan Atomic Energy Agency

Yuichi Niwa

Keio University

Hidetsugu Yoshida

Osaka University

Shigeyuki Suda

Otsuka (Japan)

Cooperative Institutions

The University of Tokyo

Geological Survey of Japan

Japan Atomic Energy Agency

National Institute of Advanced Industrial Science and Technology

Chuo University

Association for the Development of Earthquake Prediction

Central Research Institute of Electric Power Industry

Tokyo University of Science

Kawasaki Heavy Industries (Japan)

United States Geological Survey

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Offshore Fault-related Fold along the Eastern Marginal Zone of Ishikari Lowland, Hokkaido, Japan

Zisin (Journal of the Seismological Society of Japan 2nd ser ) (2023)

Takashi Ogami Shintaro Abe Masatoshi YAGI Yasuto Uchida Kenji Nishina

Distributions, characteristics, and activities of offshore fault-related folds which comprise the southern part of the Eastern Boundary Fault Zone of Ishikari Lowland (EBFIL) are clarified by conducting a high-resolution multi-channel seismic reflection survey. To determine termination point of the fault zone, we placed seven survey lines perpendicular to the fault-related folds with a total line length of 107.5 km. We choose a compact water gun (15 cubic inch) as the seismic source to obtain high-resolution imagery of the Late Quaternary and investigate activity of the fault zone. Based on seismic facies, we distinguished packages of offshore sediment (unit 2, 3 and 4, in descending order), which separated by downlap surfaces and correlated to the Middle to the Late Pleistocene. They are progressively deformed by the active fault and compose series of fault-related folds (Fo1, Fo2 and Fo3). Traces of these folds are figured out from the seismic sections obtained by this study and existing surveys. Deformation related to these folds are clearly recognized in the topography of the unit 4 base. The reliefs of strata indicate that the Fo2 fold should have uplifted seafloor at a rate of 0.09-0.20 m/ky since 300 ka. The structures, spatial distributions and growth-rates of the folds suggest that Fo1 and Fo2 should compose series of anticline developing at the front of EBFIL. Besides, Fo2 fold would compose the southern termination of the fault zone. This study has successfully demonstrated that densely operated high-resolution seismic survey can figure out distribution and activity of offshore active faults in the Late Quaternary, even at the outside of shelf.

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Seafloor Spreading

10.4294/zisin.2021-15

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Holocene Activity and the Latest Faulting Event of the Kakuda-Yahiko Fault Based on Active-fault Survey at Offshore of Echigo Plain, Central Japan

Zisin (Journal of the Seismological Society of Japan 2nd ser ) (2018)

Takashi Ogami Shintaro Abe M. Yagi Hiroshi Mori Hidekazu Tokuyama

Offshore extension of the Kakuda-Yahiko fault and its fault-propagating fold are investigated based on combination of high-resolution seismic surveys and sedimentary analysis to evaluate their Holocene activity. High-resolution multi-channel seismic surveys with the boomer sonar (13 lines) and high-frequency seismic survey with the chirp sonar (3 lines) ran across the fault line and its extension, and provided us sharp imageries of stratigraphic succession formed after the last lowstand. We can clearly recognize progressive deformation at the eastern-wing of the fault-propagating fold in the observed succession. To determine actual ages of the seismic strata, we measured radiocarbon dates from sedimentary cores obtained by 2 offshore borings and 2 vibro-coring surveys. Based on deformation of strata between 10.8 ka and 4.7 ka, averaged vertical slip rate was figured out to be 2.1 m/ky. On the other hand, we investigated temporal changes of accumulation rates at both the upthrown and the downthrown sides of the fault. Dynamic changes of the accumulation rates indicate that there were approximately 3 events at least during the last 10.8 ky and the averaged vertical slip rate was 3.0 m/ky during the period. Another focus of our study is on the latest activity of the fault. On the fault-propagating fold, we distinguished the uppermost strata younger than 0.9 ka without any deformation from these older than 2.1 ka with obvious fault deformation based on the profile obtained by the chirp-sonar seismic survey. These observations affirm that the latest event should have occurred between 0.9 ka and 2.1 ka. Furthermore, structural analysis on the deformed strata of 2.1 ka indicates that throw of the fault at the latest “single” activity was ca. 7.5 m. This study successfully demonstrated that set of parameters about the active fault including average slip rate, activity history, timing of the latest event, and associate surface displacement per activity of the fault could be elaborated from series of offshore active fault surveys.

Coring

10.4294/zisin.2017-9

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Spatial distribution of active structure and the activity in the offshore extension of the Nagaoka-Heiya-Seien Fault zone.

Japan Geoscience Union (2017)

Shintaro Abe Takashi Ogami Hiroshi Mori Kenjiro Mukaiyama Naohiro Kazui

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Progradational process of the Kiso river delta, based on the analysis of numerous core logs

The American Journal of Gastroenterology (2004)

Masaaki Yamaguchi Toshihiko Sugai Osamu Fujiwara Takashi Ogami

River delta

10.14866/ajg.2004f.0.67.0

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Seismic trenching on offshore part of the Hinagu Fault Zone, Kyushu, Japan −3D structure and paleo-seismicity of offshore dextral strike-slip fault

Japan Geoscience Union (2019)

Takashi Ogami Shintaro Abe Kenjiro Mukaiyama Shigeyuki Suda

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Effects of valley topography on run-up of the 2011 Tohoku tsunami on the Sanriku coast, northeastern Japan

Japan Geoscience Union (2017)

Takashi Ogami Toshihiko Sugai

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Evaluation of the Activity of the Yokkaichi Fault since the Late Pleistocene

The Quaternary Research (Daiyonki-Kenkyu) (2006)

Takashi Ogami Toshihiko Sugai

簡易ボーリング調査, 既存ボーリング資料の収集・解析, 14C年代測定, 地形測量にもとづき, 四日市断層の撓曲崖の地下構造とその成長過程を明らかにし, 四日市断層と養老・桑名断層の関係を検討した. 過去10,000年間における四日市断層の平均上下変位速度は1.2～1.8mm/yrであり, 桑名断層の活動度と同程度である. また, 過去7,000年間における断層変位の累積パターンは, 桑名断層のそれと一致する. さらに, 四日市断層の最近3回の活動時期と各断層イベントの上下変位量は, 桑名断層の最近3回の値とほぼ等しいと考えて矛盾しない. これらのことは, 四日市断層が少なくとも過去10,000年間, 桑名断層と同一の活動セグメントをなしているとの考えを支持する.

10.4116/jaqua.45.131

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Relative sea-level change at Nobi plain since the Last Glacial

The American Journal of Gastroenterology (2004)

Takashi Ogami Toshihiko Sugai Osamu Fujiwara

10.14866/ajg.2004s.0.213.0

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Dynamics of longitudinal river profiles associated with knickpoints since the Middle Pleistocene on the northern Sanriku Coast, NE Japan

The Quaternary Research (Daiyonki-Kenkyu) (2015)

Takashi Ogami

三陸海岸北部において中期更新世以降の海成段丘群を横断する12本の河川群を対象に,高精度数値標高モデルを用いて河床縦断形と河川遷急点を記載した.9本の河川の最下流部は直線的で河床勾配が大きな区間をなし,その上流端に顕著な遷急点が発達する.河床縦断形と地形配列の特徴から,これらの遷急点は海成段丘の形成に伴って発生し,岩盤河川の下刻によって上流側に移動していると推定した.遷急点の発生地点を特定するための遷急点移動モデルを構築し,遷急点が発生した海食崖とその形成時期を推定した.これらの遷急点の平均後退速度は5m/kyと見積もられた.

10.4116/jaqua.54.113

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Hydrologic and topographic control on recession of river knickpoints

The American Journal of Gastroenterology (2015)

Takashi Ogami

10.14866/ajg.2015s.0_100268

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