Exploring Site Response in the Taipei Basin with 2D and 3D Numerical Simulations

Abstract eng:
The city of Taipei in northern Taiwan is located on a sedimentary basin and was affected by several destructive earthquakes in the past. Recent analysis of recorded data showed significant difference between records for deep and shallow events. Spectral amplifications for stations in the central part of the basin are larger for shallow than for deep earthquakes in the low frequency range (f < 2 Hz - 3 Hz). For stations located directly along the basin edges, no clear difference is observable. We apply 3D finite-difference (FD) modelling of wave propagation in order to understand the observed peculiarities. The influence of deep and shallow earthquakes and of earthquake azimuth is explored by simulating incident S-wave front with varying incidence angles and azimuths. Furthermore, we explore 3D basin effects and evaluate the applicability of 2D numerical modeling of wave propagation for the Taipei basin by comparing simulations for 2.5D and 3D structures of the basin. We show that numerical modeling can reproduce the spectral amplification characteristics found by analysis of recorded data. We found that 3D basin effects occur at the western deep part of the basin for deep and shallow earthquakes. In the eastern part of the basin 3D effects occur only for shallow earthquakes. Our studies suggest that 3D numerical modeling is an appropriate tool to simulate ground motion parameters for the Taipei basin in the low frequency range. As bridges and high-rise buildings are very sensitive to this low frequency part such a modeling is very important.

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