| Summary: | 碩士 === 國立中央大學 === 地球物理研究所 === 93 === The Meishan fault is an earthquake fault which was displaced in the 1906 Meishan earthquake (M=7.1). The earthquake induced severe damages and killed 1,258 people. However, it is also signified as the first instrument-recorded and well-documented earthquake in Taiwan by civilized technologies. The fault was a right-lateral and slight-thrust oblique fault (1~2 m displacement) trending in the N75E direction. The northern side was lifted near Meishan and it changed to the southern side raised remote from Meishan. We revisit the Meishan fault to prepare for its 100th anniversary in 2004-2005. A relatively advanced and detailed reflection seismic survey was carried out to find new evidences which may lead better understanding of the peculiar behaviors of the fault. After collecting and analyzing 4 seismic profiles across the fault, we realize that it needs to put the Meishan fault in the regional geological framework to identify its role and meaning. The earthquake was initiated near Meishan where the fault intersected the Hsiaomei anticline by 50 degrees. There is also another significant thrust (the Chiuhsiungken fault, NS orientation) sited to the east. The merger of these three systems claims the focus of the earthquake. When the earthquake was set off, the northern side moved to the east and was hindered by the Hsiaomei anticline and the Chiuhsiungken thrust, thus was uplifted. On the other hand, far from Meishan to the west end, the southern side was relatively free to move and even uplift. An interesting compressive bending type of ‘flower structure’ was found along the fault trace given by Omori (1907). The rupture amplitudes decay quickly toward the western end, where is the Chungcheng university. The segmentation of fault occurred here and a branch (the Chenchuliaw fault) resumed. The investigation of the Meishan fault should be concentrated around Meishan, not to the western end. More investigations need be emphasized near the town of Meishan.
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