Principal horizontal stress orientations from ODP Leg 186 Sites on the deep-sea terrace of the Japan Trench prior to the 2011 Mw9.0 Tohoku-Oki, Japan, earthquake

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http://abstractsearch.agu.org/meetings/2011/FM/U53D-0090.html
Author(s): Lin, W.; Saito, S.; Sanada, Y.; Yamamoto, Y.; Hashimoto, Y.; Kanamatsu, T.
Author Affiliation(s): Primary:
Japan Agency for Marine-Earth Science and Technology, Kochi Institute, Nankoku, Japan
Other:
Kochi University, Japan
Volume Title: AGU 2011 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2011; American Geophysical Union 2011 fall meeting, San Francisco, CA, Dec. 5-9, 2011. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English. Accessed on Sept. 16, 2014
Summary: To obtain the principal horizontal stress orientations prior to the 2011 Mw9.0 Tohoku-Oki, Japan, earthquake, we analyzed wireline logging Formation MicroScanner (FMS) images and caliper data that were collected during Ocean Drilling Program Leg 186 and have not previously been analyzed for this purpose. We found stress-induced compressive failures (breakouts) and drilling-induced tensile fractures (DITFs) and obtained their azimuths. Therefore, we successfully determined principal horizontal stress orientations as of 1999 at sites in the source area of the 2011 Tohoku-Oki earthquake, on the deep-sea terrace of the Japan Trench. The maximum principal horizontal stress orientation at site 1151 of ODP Leg 186, located in an aseismic zone, was east-southeast, parallel with the plate convergence direction; and the stress orientation at site 1150 of Leg 186, in a seismically active zone, was south-southeast, suggestive of a regional stress feature due to the influence of seismic activity. Aftershocks with normal faulting mechanisms, observed in the hanging wall of the plate interface that ruptured during the Tohoku-Oki earthquake, indicate a normal faulting postseismic stress regime, which clearly differs from the stress state prior to the earthquake. Consequently, the stress state may have changed from a reverse to a normal faulting regime during the Tohoku-Oki earthquake sequence.
Year of Publication: 2011
Research Program: ODP Ocean Drilling Program
Key Words: 19 Geophysics, Seismology; Aftershocks; Earthquakes; Faults; Fractures; Japan Trench; Leg 186; Normal faults; North Pacific; Northwest Pacific; ODP Site 1150; ODP Site 1151; Ocean Drilling Program; Orientation; Pacific Ocean; Precursors; Seismicity; Stress; Tohoku-Oki earthquake 2011; Well logs; West Pacific
Coordinates: N384500 N391100 E1432000 E1432000
Record ID: 2014092575
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