Simulation of Near-fault Ground Motions at Layered Rock Sites

Simulation of Near-fault Ground Motions at Layered Rock Sites

The objective of this study is to simulate the near-fault ground motions at layered rock sites. Based on the 3D quasi-dynamic model, in which the rupture and healing processes are taken into account, the space-time slip function of rupture points on the fault plane can be determined. In this study, the slip dislocation at each rupture point on the fault plane is taken for a double couple point source, and then, the induced wave field within an infinite space can be determined in the frequency domain through the solutions of scalar potentials which are expressed by the double spectral integration form. After that, in this study, a 3D layered half-space is considered to model the site conditions where a significant soft rock layer is over the semi-infinite hard bedrock. For this case, the aforementioned wave field within the infinite space can be recognized as the incident wave within the source layer(hard bedrock), and further, the associated wave field within the upper soft rock layer can be determined on the basis of the wave scattering theory for a layered half-space. Therefore, based on the slip function at each rupture point and the Green’s function due to a double couple point source, the total ground displacement can be obtained by the integration over the finite fault plane. Finally, the time history of the near-fault ground motion can be determined by the inverse Fourier transformation from the frequency domain to the time domain. Then, the associated structural responses spectra can be carried out to evaluate the impact of the site-specific near-fault ground motions.