Excitation of Short-Period Surface Waves in Taiwan by the Hyogo-ken Nanbu Earthquake of January 17, 1995.

Abstract

Surface waves excited by the January 17, 1995 Hyogo-ken Nanbu earthquake recorded by the newly upgraded Taiwan short-period seismic network were used to perform a dispersion study. It is shown that for large and shallow earthquakes, recordings from short-period seismic networks can be effectively used for an intermediate period band (10 to 30 s) surface-wave analysis. The small station spacing of the Taiwan Seismic Network allows the application of array processing to extract high resolution phase velocities for both Love and Rayleigh waves, and to better handle the problem of surface-wave velocity determination for wave approach deviating from the great circle path. From the dispersion data so derived, a better definition of the Taiwan crustal structure is obtained. Since the general direction of the surface-wave arrival is nearly parallel to the major structural grain of Taiwan, this provides an opportunity to delineate the crustal lateral heterogeneities for different geological provinces in that region. The S-wave crustal structures from this surface-wave analysis are consistent with P-wave crustal structures from recent tomographic studies. Our results further indicate the absence of a root for the Central Range of Taiwan which rises to a height of 4, 000 m. This lack of a mountain root is also required by the recently completed Taiwan Bouguer anomaly map.