Low Coseismic Shear Stress on the Tohoku-Oki Megathrust Determined from Laboratory Experiments

Authors

Kohtaro Ujiie, University of Tsukuba
Hanae Tanaka, University of Tsukuba
Tsubasa Saito, University of Tsukuba
Akito Tsutsumi, Kyoto University
J Mori, Kyoto University
Jun Kameda, Hokkaido University
Emily E. Brodsky, University of California - Santa Cruz
Frederick M. Chester, Texas A & M University - College Station
Nobuhisa Eguchi, Japan Agency for Marine-Earth Science and Technology
S Toczko, Japan Agency for Marine-Earth Science and TechnologyFollow

Abstract

Large coseismic slip was thought to be unlikely to occur on the shallow portions of plate-boundary thrusts, butthe 11 March 2011 Tohoku-Oki earthquake [moment magnitude (M_w) = 9.0] produced huge displacements of ~50 meters near the Japan Trench with a resultant devastating tsunami. To investigate the mechanisms of thevery large fault movements, we conducted high-velocity (1.3 meters per second) friction experiments onsamples retrieved from the plate-boundary thrust associated with the earthquake. The results show a smallstress drop with very low peak and steady-state shear stress. The very low shear stress can be attributed tothe 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.

Department

Center for Coastal and Ocean Mapping

Publication Date

12-6-2013

Volume

342, Number 6163

Journal Title

Science

Pages

1211-1214

Publisher

American Association for the Advancement of Science (AAAS)

Digital Object Identifier (DOI)

10.1126/science.1243485

Document Type

Journal Article

Recommended Citation

K. Ujiie et al., "Low Coseismic shear stress on the Tohoku-Oki Megathrust determined from laboratory experiments," Science, vol. 342, no. 6163, pp. 1211–1214, Dec. 2013.