The Three-Dimensional Seismic Interpretation of Structure of the Meishan Fault Zone

• Main Authors: Sun, Wei-Hsiang, 孫偉翔
• Other Authors: Shih, Ruey-Chyuan
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/01684546975384827323

碩士 === 國立中正大學 === 地震研究所 === 103 === According to the historical records, in 1906, the 7.1 Meishan earthquake occurred in the Yunlin and Chiayi area, was the most prominent earthquake hazard happened in the southwestern Taiwan, in the last century. The Meishan fault and the surface ruptures along with that earthquake were distributed about 13.5 km. The Meishan fault was a right-lateral strike-slip fault, and the largest horizontal and vertical displacement reported by Omori (1907) was about 2.4 m and 1.8m. However, after about 100 years, the seismic activities around the Meishan fault were sort of quiet, especially in the past twenty years. The above phenomena could be considered as a stress accumulation along the fault. In this case, it will be worthwhile of studying the actual location of the Meishan fault is, and its characteristics. In this thesis, I will show the three dimensional interpretation of the subsurface structure around the fault, by using the shallow seismic reflection images those conducted by ourselves and the deeper seismic profiles acquired by CPC in the past. Three dimensional relationships between the Meishan fault, the Chiuchiungkeng fault, and the Hsiaomei anticline will be illustrated as well. The seismic profiles obtained from CPC showed that the near-surface formations were cut by many faults, and the width of fault zone is about 2-3 km. This resulting width of the fault zone is much larger than that obtained from the past study by using the shallow seismic profiles. In our study, we also proposed that the 1906 earthquake rupture was simply part of the Meishan fault zone. Those fault ruptures could merged into a main fault in the deeper strata. The three-dimensional structure of the Hsiaomei anticline showed that the anticlinal axis was horizontally offset by a displacement of about 2 km. The offset is same as that obtained from the geomorphology.