EXCITATION OF SHORT-PERIOD SURFACE-WAVES IN TAIWAN BY THE HYOGO-KEN-NANBU EARTHQUAKE OF JANUARY 17, 1995

Surface waves excited by the January 17, 1995 Hyogo-ken Nanbu earthqua ke recorded by the newly upgraded Taiwan short-period seismic network were used to perform a dispersion study. It is shown that for large an d shallow earthquakes, recordings from short-period seismic networks c an be effectively used for an intermediate period band (10 to 30 s) su rface-wave analysis. The small station spacing of the Taiwan Seismic N etwork allows the application of array processing to extract high reso lution phase velocities for both Love and Rayleigh waves, and to bette r handle the problem of surface-wave velocity determination for wave a pproach deviating from the great circle path. From the dispersion data so derived, a better definition of the Taiwan crustal structure is ob tained. Since the general direction of the surface-wave arrival is nea rly parallel to the major structural grain of Taiwan, this provides an opportunity to delineate the crustal lateral heterogeneities for diff erent geological provinces in that region. The S-wave crustal structur es from this surface-wave analysis are consistent with P-wave crustal structures from recent tomographic studies. Our results further indica te the absence of a root for the Central Range of Taiwan which rises t o a height of 4,000 m. This lack of a mountain root is also required b y the recently completed Taiwan Bouguer anomaly map.