Strong ground motion simulation for seismic hazard assessment in an urban area

Abstract

Seismic wave propagation and strong ground motion in a number of urban settings are simulated by using the pseudospectral time domain method with staggered grid real fast Fourier transform differentiation. For urban seismic study and damage prevention, simulations of the seismic wave propagation and ground motion need a comprehensive consideration of earthquake type, building structure and three-dimensional velocity structures of the crust and especially the near-surface sediments. The distribution of ground motion in an urban area varies greatly in response to geological structures. Wave interferences between the body wave and the secondary surface wave may result in peak ground motions and high collapse ratio of buildings in urban regions far away from the seismogenic fault. The simulated waveforms using an impulse point source in a 3D velocity structure can be employed to synthesize seismograms of ground motion as Green's function for any prescribed rupture scenario and source functions. The simulated results show that the synthesized seismograms coincide well with the observed seismic waveforms for the 1995 Hyogo-ken Nanbu M7.2 earthquake, which occurred in a heavily urbanized area. The simulation Green's function method is useful for predicting the strong ground motion in an urban region without observed seismic waveforms to provide a useful strong ground motion and hazard scenario for urban planning and earthquake hazard prevention. The present technique is an important supplement to the empirical Green's function method that heavily depends on the availability of local and regional seismicity. © 2007 Nanjing Institute of Geophysical Prospecting.