The post-earthquake stress state on the Tohoku megathrust as constrained by reanalysis of the JFAST breakout data

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doi: 10.1002/2017GL074027
Author(s): Brodsky, Emily E.; Saffer, Demian; Fulton, Patrick; Chester, Frederick; Conin, Marianne; Huffman, Katelyn; Moore, J. Casey; Wu, Hung-Yu
Author Affiliation(s): Primary:
University of California at Santa Cruz, Department of Earth and Planetary Sciences, Santa Cruz, CA, United States
Pennsylvania State University, United States
Texas A&M University, United States
Université de Lorraine, France
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: Geophysical Research Letters
Source: Geophysical Research Letters, 44(16), p.8294-8302. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0094-8276 CODEN: GPRLAJ
Note: In English. 21 refs.; illus., incl. sketch map
Summary: The Japan Trench Fast Drilling Project (JFAST) endeavored to establish the stress state on the shallow subduction megathrust that slipped during the M9 Tohoku earthquake. Borehole breakout data from the drill hole can constrain both the orientation and magnitude of the principal stresses. Here we reanalyze those data to refine our understanding of the stress state on the fault. In particular, we (1) improve the identification of breakouts, (2) consider a fuller range of stress states consistent with the data, and (3) incorporate new and more robust laboratory constraints on rock strength. The original conclusion that the region is in a normal faulting regime after the earthquake is strengthened by the new analysis. The combined analysis suggests that the earthquake released sufficient elastic strain energy to reset the local stress field. Abstract Copyright (2017), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 19 Geophysics, Seismology; Asia; Borehole breakouts; Boreholes; Cores; Earthquakes; Elastic constants; Equations; Expeditions 343/343T; Fabric; Failures; Far East; Faults; Geologic hazards; Honshu; IODP Site C0019; Integrated Ocean Drilling Program; Japan; Japan Trench; Japan Trench Fast Drilling Project; Marine sediments; Measurement; Natural hazards; Normal faults; North Pacific; Northwest Pacific; Orientation; Pacific Ocean; Plate convergence; Poisson's ratio; Pore pressure; Quantitative analysis; Resistivity; Risk assessment; Sediments; Seismic risk; Seismicity; Seismotectonics; Shear stress; Strength; Stress; Tectonics; Tohoku-Oki earthquake 2011; Tsunamis; West Pacific
Coordinates: N375619 N375620 E1435449 E1435447
Record ID: 2018061806
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom