Array Deployment to Observe Rotational and Translational Ground Motions along the Meishan Fault, Taiwan: A Progress Report

Abstract

Measurements in the near field of earthquakes in Japan (Takeo, 1998) and in Taiwan (Huang et al. , 2006; Liu et al. , 2009) indicate that rotational ground motions are many times larger than expected from the classical elasticity theory. The Central Weather Bureau (CWB) deployed four instrumentation sets on the campus of the National Chung-Cheng University, Chia-yi, Taiwan, in order to study in detail earthquakes in the near field for both seismology and earthquake engineering. Both rotational and translational ground motions are being monitored along the active Meishan fault, where a major earthquake occurred in 1906, more than a century ago. The deployed instruments are: (1) a 32-element seismic array in the free field, (2) a 32-element seismic array in a building, (3) a six-channel unit with a broadband seismometer and an accelerometer, and (4) a six-channel unit with an accelerometer and an external rotational velocity sensor. This short note is a progress report on this array deployment. Although 24 local earthquakes were recorded by one or more of the four instrumentation sets from 12 December 2007 to 3 July 2008, we are still in the process of upgrading equipment and improving field operations.