HR: 0800h
AN: S11C-0709    [Abstracts]
TI: Modelling of the spatio-temporal distribution of aftershocks based on rate- and state friction law
AU: * Iwata, T
EM: iwata@ism.ac.jp
AF: The Institute of Statistical Mathematics (ISM), 4-6-7 Mimami-Azabu, Minato-ku, Tokyo, 106- 8569, Japan
AU: Toda, S
EM: s-toda@aist.go.jp
AF: Active Fault Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Site 7, 1-1-1 Higashi, Tsukuba, 305-8561, Japan
AU: Ogata, Y
EM: ogata@ism.ac.jp
AF: The Institute of Statistical Mathematics (ISM), 4-6-7 Mimami-Azabu, Minato-ku, Tokyo, 106- 8569, Japan
AB: We model the spatio-temporal distribution of the aftershocks of the 1995 Kobe earthquake based on static stress change (ΔCFF) and rate- and state-dependent constitutive friction law (Dieterich, 1994). In several studies, such a type of approach reproduces the observed spatio-temporal distribution of off-fault aftershocks (e.g., Toda et al., 2003). On the other hand, for on-fault aftershocks, it is thought to be difficult to match the expected spatio- temporal distribution of aftershocks with the observed one. A slip model of mainshocks derived from a waveform inversion is necessary for the calculation of the ΔCFF. Small-scale slip discontinuities are not represented by the smoothed slip model, and the calculated ΔCFF close to the main fault also does not represent small-scale stress discontinuities. In our model, we incorporate ΔCFF caused by each of the aftershocks and the model parameters are estimated by the maximum likelihood method. We adopt a relatively simple slip model for the calculation of ΔCFF caused by the mainshock; nonetheless, the expected spatial distribution of seismicity close to the fault of the mainshock is roughly consistent with the observed one. Concerning the temporal variation of the aftershocks, the decay of the expected seismicity is slower than the observed one. The temporal behavior of Dieterich model is close to power law decay (Omori-Utsu formula) with exponent p=1. This limitation would be affected the inconsistency between expectation and observation of temporal decay in our modelling.
DE: 3245 Probabilistic forecasting (3238)
DE: 3252 Spatial analysis (0500)
DE: 3270 Time series analysis (1872, 4277, 4475)
DE: 7223 Earthquake interaction, forecasting, and prediction (1217, 1242)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
SC: Seismology [S]
MN: 2007 Fall Meeting