Abstract

The ground motion generated by buried rupture earthquakes is empirically larger than that generated by surface‐rupture earthquakes of periods 0.3–3 s. In order to understand the characteristics of the ground motion, it is important to consider the physics‐based mechanism of the generation of surface and buried faults. Dynamic rupture propagation is numerically simulated to study the generation mechanism by considering the material plasticity, using the Drucker–Prager model, in a shallow‐crust structure. The effect of energy dispersion due to plasticity decreases the rupture velocity with which the rupture propagates toward the free surface. As a result, in the case of a deep hypocenter, the stopping front generated from the bottom edge catches up to the rupture front before the rupture passes through the free surface. On the other hand, in the case of a shallow hypocenter, the stopping front does not catch up to the rupture front, and the fault ruptures the surface. The slip rate for buried faults has a larger peak and a shorter rise time than that for surface faults in the region close to the interface of the shallow crust. The ground motion generated by the source models is consistent with the motion of real earthquakes.

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