Delineating the Fault Planes of the 2006 Pingtung Doublet Earthquakes by Aftershock Locations

The 2006 Pintung doublet earthquakes (Mw=6.9) were occurred in the offshore region of southwestern Taiwan, where were rarely expected to have large earthquake. Based on the global centroid-moment-tensor(CMT) inversion result, the first one is associated with a normal-faulting and the other with a strike-slip faulting. In this study, the aftershock sequences recorded by an OBS array deployed over the source zone for one week, were relocated to estimate the true fault planes. The preliminary relocation results indicate that the most events in the northern part were aligned with the eastward dipping fault plan of the fist mainshock, and the remnants were spread sparsely but seemed to follow the westward dipping fault plan of the second mainshock. This result is not usually expected because the hypocenter of the first event was located southern than that of the second one. However, the more detailed examination is still needed.