Presenter: Ching-Yu Cheng
Date: 2017/03/30
Abstract
1906 Ｍ7.1 Meishan earthquake occurred near Chiayi city in southwestern Taiwan and resulted in more than three thousands casualties and six thousands of buildings collapsed. Based on the geological survey, the Meishan fault zone a right- lateral strike-slip fault with a length of 25 kilometers, was the main contributor for this event. In previous studies, many researchers have done lot of investigation about the Meishan Fault zone, including geologic researches at surface and seismic explorations at shallow crust. However, there is still limited information about 3-D shallow crustal structure of this study area. Therefore, we deployed 100 Texan instruments (~2 km interval) between Aug. and Nov. 2015, covered around the Meishan Fault zone. We obtained a 3-D shear wave shallow crustal velocity structure using ambient noise tomography. The reliable periods of phase velocity from Rayleigh wave are 0.6 to 6.8 seconds, which correspond to around 0-5 km at depths. As a result, the sub-surface structure around the Meishan fault zone is very complex. The structures of the basement varied across the Meishan fault zone: the basement is thicker in the north of the fault zone than that in the south. Also, Xiaomei anticline near the fault zone is observed from this study.
Reference
Chen, W.S., Yeh, M.G., Yang, C.C., Shih, R.C., Lin, C.W. & Hou, C.S., 2006. Structural characteristics of the Meishan fault, Bulletin of the Central Geological Survey, 19, pp. 135–151, MOEA
Chen, K. X., Kuo-Chen, H., Brown, D., Li, Q., Ye, Z., Liang, W.T., Wang, C.Y. & Yao, H., 2016. Three-dimensional ambient noise tomography across the Taiwan Strait: The structure of a magma-poor rifted margin, Tectonics, 35, doi:10.1002/2015TC004097.
Fang, H., Yao, H., Zhang, H., Huang, Y.C. & Van Der Hilst, R.D., 2015. Direct inversion of surface wave dispersion for 3-D shallow crustal structure based on ray tracing: Methodology and application, Geophys. J. Int., 201, 1251–1263, doi:10.1093/gji/ggv080.