Simulation of rupture process in heterogeneous stress field estimated from active fault information: Application to the Uemachi and Ikoma fault systems

Yuko Kase, Haruko Sekiguchi, Tatsuya Ishiyama, Haruo Horikawa, Kenji Satake and Yuichi Sugiyama

Laterally heterogeneous stress field is introduced into dynamic rupture simulation for realistic modeling of earthquakes. We estimated heterogeneous stress fields from distributions of average geological uplift rates (Sekiguchi et al., in this report) and fault geometry, and simulated spontaneous rupture processes. We applied this new method to rupture processes on the Uemachi and Ikoma fault systems, intraplate active faults in the Osaka sedimentary basin, central Japan. Our simulations yield quite smooth rupture propagation but heterogeneous slip distribution. The rupture area depends on fault geometry and initial crack location. When an initial crack is located at a wide region of large stress drop, rupture results in a large area.

Fig. 1. Heterogeneous distribution of initial stress field for the Uemachi fault system (1-segment model). Grey areas indicate where rupture does not occur inside sediment layer. (a) Average uplift rate along fault trace (Sekiguchi et al., 2003). (b) Slip distribution on the fault estimated by Sekiguchi et al. (2003). (c) Stress drop distribution on fault estimated by Sekiguchi et al. (2003). (d) Strength excess distribution on fault estimated from the stress drop distribution.

Fig. 2. Rupture processes of the Uemachi fault system (1-segment model). (a) A hypocenter is located near the northern end of the fault system. (b) A hypocenter is located near the southern end of the fault system.