Low coseismic shear stress on the Tohoku-Oki megathrust determined from laboratory experiments

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doi: 10.1126/science.1243485
Author(s): Ujiie, Kohtaro; Tanaka, Hanae; Saito, Tsubasa; Tsutsumi, Akito; Mori, James J.; Kameda, Jun; Brodsky, Emily E.; Chester, Frederick M.; Eguchi, Nobuhisa; Toczko, Sean
Integrated Ocean Drilling Program, Expedition 343 and 343T Scientists, College Station, TX
Author Affiliation(s): Primary:
University of Tsukuba, Graduate School of Life and Environmental Sciences, Tsukuba, Japan
Other:
Kyoto University, Japan
Hokkaido University, Japan
University of California at Santa Cruz, United States
Texas A&M University, United States
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: Science
Source: Science, 342(6163), p.1211-1214. Publisher: American Association for the Advancement of Science, Washington, DC, United States. ISSN: 0036-8075 CODEN: SCIEAS
Note: In English. 25 refs.; illus.
Summary: Large coseismic slip was thought to be unlikely to occur on the shallow portions of plate-boundary thrusts, but the 11 March 2011 Tohoku-Oki earthquake [moment magnitude (Mw) = 9.0] produced huge displacements of ∼50 meters near the Japan Trench with a resultant devastating tsunami. To investigate the mechanisms of the very large fault movements, we conducted high-velocity (1.3 meters per second) friction experiments on samples retrieved from the plate-boundary thrust associated with the earthquake. The results show a small stress drop with very low peak and steady-state shear stress. The very low shear stress can be attributed to the abundance of weak clay (smectite) and thermal pressurization effects, which can facilitate fault slip. This behavior provides an explanation for the huge shallow slip that occurred during the earthquake.
Year of Publication: 2013
Research Program: IODP Integrated Ocean Drilling Program
Key Words: 18 Geophysics, Solid-Earth; 19 Geophysics, Seismology; Boreholes; Coseismic processes; Decollement; Earthquakes; Expedition 343; Expedition 343T; Experimental studies; Friction; Integrated Ocean Drilling Program; Japan Trench; Laboratory studies; North Pacific; Northwest Pacific; Ocean floors; Pacific Ocean; Permeability; Plate boundaries; Plate tectonics; Shear stress; Slip rates; Thrust sheets; Tohoku-Oki earthquake 2011; West Pacific
Coordinates: N375619 N375620 E1435449 E1435447
Record ID: 2014014651
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