TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 63 (No. 3), pp. 171-185, 2011

Rate/state Coulomb stress transfer model for the CSEP Japan seismicity forecast

Shinji Toda1 and Bogdan Enescu2

1Disaster Prevention Research Institute (DPRI), Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan
2National Research Institute for Earth Science and Disaster Prevention (NIED), 3-1 Tennodai, Tsukuba, Ibaraki 305-0006, Japan

(Received June 25, 2010; Revised January 13, 2011; Accepted January 13, 2011; Online published March 4, 2011)

Abstract: Numerous studies retrospectively found that seismicity rate jumps (drops) by coseismic Coulomb stress increase (decrease). The Collaboratory for the Study of Earthquake Prediction (CSEP) instead provides us an opportunity for prospective testing of the Coulomb hypothesis. Here we adapt our stress transfer model incorporating rate and state dependent friction law to the CSEP Japan seismicity forecast. We demonstrate how to compute the forecast rates of large shocks in 2009 using the large earthquakes during the past 120 years. The time dependent impact of the coseismic stress perturbations explains qualitatively well the occurrence of the recent moderate size shocks. Such ability is partly similar to that of statistical earthquake clustering models. However, our model differs from them as follows: the off-fault aftershock zones can be simulated using finite fault sources; the regional areal patterns of triggered seismicity are modified by the dominant mechanisms of the potential sources; the imparted stresses due to large earthquakes produce stress shadows that lead to a reduction of the forecasted number of earthquakes. Although the model relies on several unknown parameters, it is the first physics based model submitted to the CSEP Japan test center and has the potential to be tuned for short-term earthquake forecasts.
Key words: Coulomb stress change, rate and state friction, seismicity forecast, CSEP Japan.

Corresponding author E-mail: toda@rcep.dpri.kyoto-u.ac.jp

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