Research activities on submarine landslides in gentle continental slope

Author(s): Morita, S.; Goto, S.; Miyata, Y.; Nakamura, Y.; Kitahara, Y.; Yamada, Y.
Author Affiliation(s): Primary:
Geological Survey of Japan, Ibaraki, Japan
Other:
Yamaguchi University, Japan
University of Tokyo, Japan
Kochi University, Japan
Kyoto University, Japan
Volume Title: AGU 2013 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2013; American Geophysical Union 2013 fall meeting, San Francisco, CA, Dec. 9-13, 2013. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: In the north Sanrikuoki Basin off Shimokita Peninsula, NE Japan, a great number of buried large slump deposits have been identified in the Pliocene and younger formations. The basin has formed in a very gentle continental slope of less than one degree in gradient and is composed of well-stratified formations which basically parallel to the present seafloor. This indicates that the slumping have also occurred in such very gentle slope angle. The slump units and their slip surfaces have very simple and clear characteristics, such as layer-parallel slip on the gentle slope, regularly imbricated internal structure, block-supported with little matrix structure, widespread dewatering structure, and low-amplitude slip surface layer. We recognize that the large slump deposits group of layer-parallel slip in this area is an appropriate target to determine "mechanism of submarine landslides", that is one of the subjects on the new IODP science plan for 2013 and beyond. So, we started some research activities to examine the feasibility of the future scientific drilling. The slump deposits were recognized basically by 3D seismic analysis. Further detailed seismic analysis using 2D seismic data in wider area of the basin is being performed for better understanding of geologic structure of the sedimentary basin and the slump deposits. This will be good source to extract suitable locations for drill sites. Typical seismic features and some other previous studies imply that the formation fluid in this study area is strongly related to natural gas, of which condition is strongly affected by temperature. So, detailed heat flow measurements was performed in the study area in 2013. For that purpose, a long-term water temperature monitoring system was deployed on the seafloor in October, 2012. The collected water temperature variation is applied to precise correction of heat flow values. Vitrinite reflectance analysis is also being carried out using sediments samples recovered by IODP Expedition 337, which is conducted in a part of the study area from July through September in 2012. The values of vitrinite reflectance will be available for modeling thermal history in the sedimentary basin. A science meeting and a field trip were held in Miyazaki Prefecture in September, 2012. At the field trip, we observed typical geologic structures related to slumping and dewatering in Nichinan Group, which are good onshore objects so as to share the aspects of the slump deposits in the Sanrikuoki Basin among the community. This occasion is aimed at sharing better scientific understanding on slumping and related dewatering and also at identifying the issues for planning the scientific drilling. This study uses the 3D seismic data from the METI seismic survey "Sanrikuoki 3D" in 2008. The seismic analysis, the vitrinite reflectance analysis, and the science meeting and the field excursion in Miyazaki were supported by the foundation of feasibility studies for future IODP scientific drillings by JAMSTEC CDEX in 2012-2013.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 07 Marine Geology and Oceanography; Aomori Japan; Asia; Continental slope; Expedition 337; Far East; Honshu; Integrated Ocean Drilling Program; Japan; Kyushu; Mass movements; Miyazaki Japan; North Pacific; Northwest Pacific; Pacific Ocean; Sanrikuoki Basin; Shimokita Peninsula; Slumping; West Pacific
Coordinates: N411035 N411036 E1421202 E1421201
Record ID: 2015063094
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