The response of Taipei basin upon earthquake excitation was studied using records of recent earthquakes. The strong-motion database includes records obtained at 32 stations of the Taipei TSMIP network from 83 deep and 142 shallow earthquakes (M > 4.0) that occurred in 1992-2004. The characteristics of frequency-dependent site response were obtained as spectral ratios between the actual earthquake records (horizontal components) and those modelled for a hypothetical Very Hard Rock (VHR) condition. The models for VHR spectra of Taiwan earthquakes had been recently proposed by Sokolov et al. (2005b, 2006). Analysis of site response characteristics and comparison with simple I D models of the soil column resulted in the following conclusions: (1) The spectral ratios throughout the basin obtained from deep earthquakes (depth > 35 km) exhibit good agreement with the theoretical ratios calculated using the ID models constructed using available geological and geotechnical data. (2) The spectral ratios obtained from shallow earthquakes show influence of. (a) surface waves generated when travelling from distant sources to the basin and (b) relatively low-frequency (< 1 - 2 Hz) waves generated within the basin. (3) Some shallow earthquakes produce extremely high amplification at frequencies 0.3 - 1 Hz within the basin that may be dangerous for high-rise buildings and highway bridges. (4) The obtained results may be used in probabilistic seismic microzonation of the basin when many possible earthquakes located at various distances are considered. 2D and 3D simulation is necessary to model the seismic influence from particularly large earthquakes.
