JFAST constraints on the Tohoku earthquake fault

Author(s): Brodsky, E. E.; Mori, J. J.; Chester, F. M.; Kodaira, S.
Author Affiliation(s): Primary:
University of California Santa Cruz, Santa Cruz, CA, United States
Kyoto University, Kyoto, Japan
Texas A & M University, Geology & Geophysics, College Station, TX, United States
Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
Volume Title: AGU 2015 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2015; American Geophysical Union 2015 fall meeting, San Francisco, CA, Dec. 14-18, 2015. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The Japan trench fast drilling expedition (JFAST) demonstrated that the fault zone of the Mw 9.0 Tohoku earthquake at the drill site near the trench was weak during slip. Four different lines of evidence led to this conclusion: (1) the low temperature anomaly on the fault zone, (2) the stability of the borehole indicating low deviatoric stress, (3) the high fraction of scaly clay in the narrow fault zone in the core, and (4) laboratory experiments on recovered fault material showing low friction under undrained conditions. Recent measurements of low temperature from the Wenchuan Fault Zone scientific drilling project suggest that friction may have been low at that site as well. The evidence for low deviatoric stresses during slip favors an asperity model where failure is determined by locally strong spots in a pervasively weak fault. During the 9-month JFAST observatory deployment, a rich array of behavior after the earthquake was revealed including evidence for fluid pulsing through the fault zone in response to local aftershocks. Capturing the healing and relocking of a fault zone is still an open challenge to fault zone drilling.
Year of Publication: 2015
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 19 Geophysics, Seismology; Asia; Earthquakes; Far East; Fault zones; Faults; Honshu; Integrated Ocean Drilling Program; Japan; Japan Trench; Japan Trench Fast Drilling Project; North Pacific; Northwest Pacific; Pacific Ocean; Seismicity; Seismotectonics; Tectonics; Tohoku-Oki earthquake 2011; West Pacific
Record ID: 2016047088
Copyright Information: GeoRef, Copyright 2017 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States

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