| Summary: | 碩士 === 國立中央大學 === 應用地質研究所 === 96 === This study estimates shear-wave velocity structure of Songshan Formation in Taipei basin using shear-wave velocity data and standard penetration test data (SPT-N) from boring and testing data at free-field strong-motion station sites and Geo2005 database, and other sources. Geostatistical analysis of semivariograms and cross-semivariograms in 3D and cokriging method was used for the estimation.
Structural analyses of shear-wave velocity data and SPT-Ns show good spatial relations in each semivariogram and cross-semivariogram. Therefore, shear-wave velocity was used as a primary variable and SPT-N as a secondary variable in the cokriging method. The result is a 3D regular grid digital model, and is shown by a set of contour maps and profile maps.
Shear-wave velocity value in the Songshan Formation increases with depth; it is about 100~200m/s within 10m depth and increases to 400~500m/s at about 45m depth. Horizontal variation of Shear-wave velocities may be shown by the variation of average shear-wave velocity within 30m depth (Vs30). The Vs30 map shows low value (160~180m/s) at Zhongshan District, and shows moderately low value (180~200m/s) at Beitou, Shilin, Datong, Zhongshan, Zhongzheng, Daan, Xinyi, Songshan District and Sanchong City. Shear-wave velocities increase from the above-mentioned low and moderately-low zones to the southwest, and reach a moderate value (220~240m/s) at Sinjhuang, Banciao, Junghe and Yunghe. It reaches 260m/s at Shulin and Tucheng. Result of this study is similar with previous researches in general, but it shows more details and lower estimation error in the variation of shear-wave velocities.
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