Topography Effects on Frequency-dependent Traveltimes and Amplitudes from Regional Earthquakes

Abstract:

Drastic topography changes have significant effects on the propagation of seismic waves, which leads to perturbations in waveforms and therefore the arrival times and amplitudes of seismic phases. Previous studies have focused on the influence of topography on the peak amplitudes of earthquake-induced strong ground motions in order to make realistic and reliable assessment of seismic hazard. Various of factors contribute to the topography-induced waveform changes, including not only the geometrical shape of the surface itself, but also the path-related incidence angles of the seismic waves which are dependent on the location of the receiver site as well as the azimuth, distance and depth of the earthquake. In this study, we conduct a quantitative assessment on the changes to the arrival times and amplitudes of regional seismic phases caused by the topography-induced waveform perturbations. Synthetic seismograms calculated by the finite-difference method in three-dimensional anelastic structure with realistic surface topography are used to investigate the effect of topography coupled with the path-related factors on the frequency-dependent phases and amplitudes. The resulting quantitative assessments of topography effects can be used to estimate the potential biases in seismic tomography due to the omission of topography in modeling regional seismic waveforms.