| 英文摘要 |
Taiwan is located at a convergent plate boundary on the Circum-Pacific seismic belt, accompanied by high seismicity and complex tectonics. The Western Coastal Plain and Western Foothills are located along the deformation front of the Taiwan orogen. This area includes highly active faults and a complex seismogenic structure that have historically caused significant damage. The densely populated cities are situated on thick alluvium and threatened by seismic-wave amplification and soil liquefaction. A temporary seismic network had been operated by the National Center for Research on Earthquake Engineering (NCREE) between 2006 and 2010, with 48 broadband seismometers and an average interstation distance of ~10 km, set up to monitor the seismicity surrounding the three Science Parks to further study the characteristics of ground motion and fault activity. Since the basic theorem of ambient seismic noise analysis has been verified, investigations of subsurface velocity structures have provided important constraints in various parts of the world, with routine data processing occurring over the past decade. In this study, the quality of data of the daily vertical component was preliminarily assessed to calculate the cross-correlation function (CCF) for each station pair in the 1-15 s period band. The daily CCFs were stacked to retain coherent signals for acquiring Rayleigh-wave phase-velocity dispersion curves. Tomography was applied to construct 1-10 s Rayleigh-wave phase-velocity maps with 0.04° grid spacing. Lateral velocity variations showed dramatic patterns among different geologic provinces. Shallow crustal S-wave velocity (Vs) structures will be obtained for further comparison with data on active faults, seismogenic structures, groundwater distribution, etc. The Vs structures will also help to construct strong ground motions, which is particularly important for seismic hazard mitigation of the densely populated metropolitan areas in western Taiwan. |
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