Shallow S-Wave Velocity Structures of the Tiehchenshan Region in Taichung-Miaoli Area, Taiwan, Using Array Records of Microtremors

• Main Authors: Che-Lun Yang, 楊哲倫
• Other Authors: Huey-Chu Huang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/65877449571723415789

碩士 === 國立中正大學 === 地震研究所 === 100 === Shear-wave velocities have widely been used for earthquake ground-motion site characterization. Thus, the shallow S-wave velocity structures of the Tiehchenshan region in the Tiachung-Miaoli area are investigated using the array records of microtremors at 19 sites. The dispersion curves at these sites are calculated using the f-k method (Capon, 1969); then, the S-wave velocity structures of the Tiehchenshan region are estimated by employing the surface wave inversion technique (Herrmann, 1991). At frequencies lower than about 3 Hz, the propagation directions are concentrated between the northwest and southwest quadrants. The generation of these may be attributed to the ocean waves of the Taiwan Strait. If the S-wave velocity of the bedrock is assumed to be 2200 m/s, the depths of the alluvium are between 1300 m and 2800 m. S-wave velocity gradually decreases from east to west at the depths less than 1200 m. At the depths between 1200m and 4000m, the higher Vs values appear at the north and the south of the region while the lower values are at the east and the west. Our results are in good agreement with the available geological and geophysical information at the Tiehchenshan region.