Strong Ground Motion Simulations of theMw 7.9 Wenchuan Earthquake Using the Empirical Green’s Function Method

Abstract

The M w 7.9 Wenchuan earthquake shocked China as well as the world, not only because of its great moment magnitude but also due to the terrible casualties. The complex nature of this earthquake combined with its damage brings the need for studies that assess the seismological characteristics of the M w 7.9 Wenchuan earthquake. In this study, we present the strong ground motion simulation of the great earthquake using the empirical Green’s function (EGF) method. First, we select four M w 4.9 and 5.0 aftershocks, the motions of which are used as Green’s functions. The source parameters of the aftershocks including fault size and stress drop are estimated for the simulation. Then the source model of M w 7.9 with asperities (strong‐motion generation area) is derived using forward modeling by trial and error. To validate the accuracy of the proposed source model, strong ground motions at nine stations are synthesized by the EGF method. The simulated strong ground motions are compared with the observed records in terms of acceleration waveforms, velocity waveforms, and pseudoacceleration response spectrum. Despite some discrepancy, the synthesized motions at most stations show good agreement with the observed records. In the proposed source model, the stress drop of the three asperities on the source fault is about 10 MPa, whereas the ratio of combined area to the rupture area is 0.24, which approximates 0.22 from the empirical relationship.