Auxiliary material for Paper 2011GL047834



Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer
 


Shinji Toda 
Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan


Ross S. Stein 
U.S. Geological Survey, Menlo Park, California, USA


Jian Lin 
Woods Hole Oceanographic Institution, Woods Hole, Massachusetts, USA


Toda, S., R. S. Stein, and J. Lin (2011), Widespread seismicity excitation throughout central Japan following the 2011 M=9.0 Tohoku earthquake and its interpretation by Coulomb stress transfer, Geophys. Res. Lett., 38, L00G03, doi:10.1029/2011GL047834.

Introduction



This auxiliary material session contains three figures.



1. 2011gl047834R-fs01.eps 
Coulomb stress changes resolved on the nodal planes of the background earthquakes as proxies of local or regional fault structure in Chubu and Kinki districts. (a) Fault plane solutions since 1997 (depth less than or equal to 20 km). (b) Maximum Coulomb stress change from each pair of nodal planes.



2. 2011gl047834R-fs02.eps 
(Left panel) Seismic response of the entire Japan to the M=9.0 Tohoku mainshock for M greater than or equal to 1.0 seismicity (90 days post-mainshock compared to 1.2-years pre-mainshock), with a smoothing radius of 20 km, using the JMA PDE catalog downloaded on 10 June 2011. (Right panel) Peak ground acceleration recorded by the NIED K-NET/KiK-net strong motion seismographic network (open black squares). The observed seismicity rate changes are poorly correlated with the accelerations, suggesting that the dynamic stresses or intensity of shaking does not appear to control the seismicity response.



3. 2011gl047834R-fs03.eps 
Here we resolve the Coulomb stress change on the nodal planes of post-Tohoku earthquakes (11 March - 17 June 2011, depth less than or equal to 20 km) in the boxes which have either very few pre-Tohoku focal mechanisms, such as A, B, D, I, M, and N; or boxes in which the focal mechanisms after Tohoku profoundly changed (J, site of the 11 April 2011 Mw=6.7 Iwaki aftershock). Some 93% (258 out of 278) of the aftershocks in box J strike on nodal planes brought closer to Coulomb failure by the Tohoku mainshock.