Dynamic rupture scenarios for strong ground motion prediction
Abstract
Spontaneous rupture models provide physically reasonable rupture processes under presumed fault geometry and stress field. We propose that dynamic rupture models based on geological or geomorphological data are used as earthquake scenarios for strong ground motion prediction. We apply our method to possible sources of earthquake occurring on the Uemachi fault systems. The Uemachi fault system runs just underneath the western part of Osaka plain, extends about 45 km, and dips 60 degrees to the east. We model the fault geometry from the surface traces and the shape of the Osaka basin-floor. The stress condition is presumed based on slip distributions on the fault. Spatially varied cumulative slip distribution along the strike of the Uemachi fault system was obtained by reflection surveys, borehole data, etc. The borehole data at a site along the fault showed that the vertical slip on the earth's surface due to the last event was between 1.6 to 2.4 m (Sugiyama et al., 2003). Combining these data, we presume an prototype of the slip distribution along strike. The slip distribution along dip is modeled through simulations of spontaneous ruptures under vertically depth-dependent stress conditions to realize spontaneously stopping rupture near the bottom of the seismogeneic zone. Onto this large-scale heterogeneous slip distribution model, we add fractal heterogeneities in small-scale created from different random numbers. These slip distributions are converted to the distributions of static stress drop. For each stress drop model, some hypocenter locations are assumed. We calculate dynamic rupture processes by the finite-difference method (Kase, 2010), assuming the slip-weakening friction law. Rupture area and rupture time on each point depend on stress model and hypocenter location. Based on these rupture scenarios, we simulate lower frequency components of ground motion by the finite-difference method (Pitarka, 1999) excluding the shallow sediment above the engineering basement. Higher frequency components are computed by the stochastic Green's function method (Onishi and Horike, 2000). Effects of the shallow alluvium layers are calculated by 1D multi-reflection theory considering nonlinear effect by equivalent linear technique using a computer code DYNEQ (Yoshida and Suetomi, 1996).
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S43C2259K
- Keywords:
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- 7200 SEISMOLOGY;
- 7209 SEISMOLOGY / Earthquake dynamics;
- 7212 SEISMOLOGY / Earthquake ground motions and engineering seismology;
- 7290 SEISMOLOGY / Computational seismology