TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 12), pp. 1239-1243, 2012

Coulomb stress change for the normal-fault aftershocks triggered near the Japan Trench by the 2011 Mw 9.0 Tohoku-Oki earthquake

Tamao Sato1, Shinya Hiratsuka1, and Jim Mori2

1Department of Earth and Environmental Sciences, Hirosaki University, Hirosaki, Japan
2Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan

(Received December 27, 2011; Revised March 19, 2012; Accepted April 6, 2012; Online published January 28, 2013)

Abstract: Coulomb stress triggering is examined using well-determined aftershock focal mechanisms and source models of the 2011 Mw 9.0 off the Pacific coast of Tohoku Earthquake. We tested several slip distributions obtained by inverting onshore GPS-derived coseismic displacements under different a priori constraints on the initial fault parameters. The aftershock focal mechanisms are most consistent with the Coulomb stress change calculated for a slip distribution having a center of slip close to the trench. This demonstrates the capability of the Coulomb stress change to help constrain the slip distribution that is otherwise difficult to determine. Coulomb stress changes for normal-fault aftershocks near the Japan Trench are found to be strongly dependent on the slip on the shallow portion of the fault. This fact suggests the possibility that the slip on the shallow portion of the fault can be better constrained by combining information of the Coulomb stress change with other available data. The case of normal-fault aftershocks near some trench segment which are calculated to be negatively stressed shows such an example, suggesting that the actual slip on the shallow portion of the fault is larger than that inverted from GPS-derived coseismic displacements.
Key words: Off the Pacific coast of Tohoku Earthquake, Tohoku-Oki earthquake, Coulomb stress change, giant earthquake, slip near the trench, outer rise, Japan Trench.

Corresponding author E-mail: tamao@cc.hirosaki-u.ac.jp

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