| Summary: | 碩士 === 國立臺灣大學 === 地質科學研究所 === 105 === In this study, we aim to better constrain the shallow seismic structure (<10 km) of Taiwan by utilizing the short period (3-7 seconds) empirical Green’s functions (EGFs) of Rayleigh waves extracted from ambient seismic noise. To improve the data coverage, continuous data recorded by 6 seismic networks during the time period from 2006 to 2007 are used to derive the EGFs between all the cross-network station pairs. With this unprecedented data set, we are able to build up high resolution 3-D Vs and Vs azimuthal anisotropy models for the shallow crust of Taiwan, using a wavelet-based multi-scale inversion technique.
Robust features both in Vs and Vs anisotropy variations of the shallow crust are obtained in the resulting 3-D models. The strong Vs lateral variations are closely related to the surface geology, and the patterns of Vs anisotropy are mostly dominated by structure-related anisotropy, with fast polarization direction generally parallel to the mountain ranges. With the new results, and our recent studies with broad-band EGFs and borehole noise interferometry, we conclude that the stress-aligned anisotropy is likely confined in the near-surface depths (< ~1 km).
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