Shallow Shear-Wave Velocity Structures of Strong-Motion Stations in the Kaohsiung-Pingtung Area Using Receiver Function Analysis

Shallow Shear-Wave Velocity Structures of Strong-Motion Stations in the Kaohsiung-Pingtung Area Using Receiver Function Analysis

Kaohsiung City and Pingtung County are located in southern Taiwan and are bounded on the west side by several active faults. The shallow velocity structure of the thick alluvium basin in this area should be delineated to understand the seismic site effect of strong ground motion. The receiver function(RF) technique is a conventional method for studying the structure of the crust and the upper mantle beneath a seismometer. However, recently RF analysis of high-frequency acceleration seismograms has proven feasible for estimating shallow structures. This study applied the RF technique to the strong-motion records of almost one hundred TSMIP stations in the Kaohsiung-Pingtung area to estimate the shallow shear-wave velocity structures. The averaged RFs of all stations exhibit obvious variations because of different geologies and site conditions. After the forward modeling of RFs on the basis of a genetic algorithm(GA) search, the shallow shear-wave velocity structures beneath all the strong-motion stations in the Kaohsiung-Pingtung area were estimated to delineate the isovelocity contour maps of the main formation interfaces and produce a preliminary shallow 3D velocity model.