2006 Taiwan PingTung Aftershocks Locations and Preliminary Tomography from OBS Data

An array of 11 portable Ocean Bottom Seismometers (OBS) was deployed to collect aftershock sequences of two 6.9ML main-shocks occurred on December 26, 2006, off PingTung, Taiwan. One day after the main shocks, more than four hundreds aftershocks with magnitude larger than 2Mb were relocated from these OBSs records. According to the northern portion of the clustered aftershocks, the fault plane of the second main shock is trending NW-SE strike with a high angle westward dip. In contrast, the distribution of the southern portion of the aftershocks corresponds to a low angle westward dipping fault plane. Our preliminary tomographic results show that a high/low P-wave velocity boundary in NW-SE direction exist in the deeper offshore region and propagates to northeastward with increasing depth. It was supposed the high P-wave velocity zone can be associated with the subducting slab of the Eurasia plate.