摘要(英) |
Shallow-Depth Velocity Structure in Southwestern Taiwan from Short-Period Surface-Wave Dispersion Data
Hung-Cheng Chang
ABSTRACT
Using fundamental-mode Rayleigh- and Love-wave with periods between 1 and 8 seconds, we inferred the shallow-depth velocity structure in southwestern Taiwan. In this study, group velocities were measured by applying the multiple-filter technique. In addition, the phase-matched filter was also employed to refine these dispersion curves. For constructing a 3-D S-wave structure under southwestern Taiwan, we first divided the study region into 28 subregions. Each subregion has a size of 0.2°×0.2°. Second, by a tomographic inversion, images of Rayleigh- and Love-wave group velocities in southwestern Taiwan can be expressed. Subsequently, the 1-D S-wave velocity structure of each subregion was obtained through the simultaneous inversion of both Rayleigh- and Love-wave. Finally, these 1-D structures were combined to construct a 3-D structure in the study region. Results show that the higher velocity distributes in the northeast of study region, and the lower velocity distributes in the southwest one. On the other hand, the depth of upper crust is estimated to be about 9 to 12 km according to the distribution of S-wave velocity. Additionally, several anomalous velocities were also pointed out in the study region, such as Peikang high, Taichung area and Gutingkeng mudstone of south Taiwan. Perhaps, this is related with Matemorphic grad and lithology. |
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