[S04-P] Poster

[S04-P-07] Revisiting source parameters of the 1906 Meishan, Taiwan earthquake from full-waveform measurements of historical records

^○Yiwun Liao¹, Ming-Che Hsieh², Kuo-Fong Ma¹ (1.Department of Earth Sciences, National Central University, Taiwan, 2.Sinotech Engineering Consultants, INC, Taiwan)

The 1906 Meishan earthquake (M7.1) was one of the largest damaging earthquakes in Taiwan in the early 20th century. Historical literatures and recent studies showed that the Meishan earthquake was related to the Meishan Fault and had a right-lateral faulting mechanism striking in east-west direction. With the historical Omori records at station Taipei, Taichung and Tainan, we carried out a waveform simulation of the 1906 Meishan earthquake for understanding source rupture properties of the 1906 Meishan earthquake and the yielding predicting ground-motion in the region. A two-step waveform simulation based on SGT (strain Green's tensor) is carried out for this attempt. In the first step, possible fault models of the 1906 Meishan earthquake from geological survey and recent studies are compiled for simulation. As the preliminary results, with an east-west strike faulting mechanism as Meishan fault, the synthetic waveforms and intensity maps were not well explained. We, thus, further carried out a grid-search in focal mechanism by fitting first-motion and shear-wave polarities of historical records and synthetics to evaluate possible focal mechanism. By comparing the simulated intensity distribution maps with the historical records, the Meishan earthquake is suggested to be associated with a north-south striking thrust faulting mechanism. Also by comparing the converted waveforms from the 1999 Chiayi earthquake to the Gray-Milne seismograms recorded at the ancient station Penghu and Tainan, the similarity of the waveforms also convinces that the Meishan earthquake might have a similar focal mechanism of a north-south striking thrust fault with the 1999 Chiayi earthquake. According to our results and the distribution of the aftershocks, the surface rupture of the Meishan fault might be a transfer fault between two thrust faulting systems in the western coastal plain of Taiwan.