1906 Meishan earthquake revisit: thrust faulting mechanism?

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 1906 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 1906 Meishan earthquake is suggested to be associated with a north-south striking thrust faulting mechanism. This might indicate that the rupture of the Meishan fault is a transfer fault between two thrust faulting systems in the western coastal plain of Taiwan. The fault systems in the western part of Taiwan might be primarily dominated by the north-south striking thrust faults even though an east-west striking surface rupture with a strike-slip mechanism was found after the Meishan earthquake.