Crustal anisotropy in north Taiwan from shear-wave splitting

Using the seismic data recorded by 13 seismic stations in north Taiwan from July 1991 to December 2002, this study analyzes the feature of shear-wave splitting in north Taiwan by SAM method of shear-wave splitting. The results show that predominant polarization directions of fast shear-waves at Yilan basin strikes to nearly E-W, while polarization directions at mountain ranges (Western Foothill, Hsueshan Range and Central Range) are in NNE or NE direction. Polarizations are scattered if the stations are on seashore or on island, and often have two predominant polarizations, which may be caused by irregular topography or complicated local tectonics. From the spatial distribution of time delays, we also find that taking station TWE as a boundary, time delays at station TWE and north of the station are longer than those at south of the station. It possibly suggests that anisotropy at station TWE and north of the station are stronger than anisotropy at south of the station.