Seismic and Tectonic Characteristics of the South-Western Taiwan Offshore Area (3)

In southwestern Taiwan, the South China Sea Plate subducts eastward beneath the Philippine Plate. The northern prolongation of Manila Trench, however, is colliding obliquely with the Eurasia Continental Shelf with a northwestern direction, creating the Taiwan Orogen. This subduction-collision system has a very complex tectonic environment which is characterized by variable seismic activities. Moreover, many different tectonic units are also observed in the vicinity, such as Luzon and Ryukyu transform plate boundary (LRTPB) and ocean and continental boundary (COB), where visible changes of bathymetry and earthquake distribution occurs. The presence of the Out of Sequence Fault (OOST) in the Manila accretionary wedge is even considered to be the most tsunamigenic structure. Generally, the southeastern Taiwan offshore area is considered as a low seismic potential area. Meanwhile, the occurrence of the 2006 December Mw 7.2 Pingtung earthquake and the 2012 October Mw 5.5 Kaohsiung earthquake have obtained the attention from publics. Furthermore, a recent report of USGS has pointed out that the Manila Trench could have high potential for generating both local and Pacific-wide tsunamis. Thus, it is important to clarify the role and nature of different geological features in the area. In this project, we plan to deploy a temporal ocean bottom seismic network in the vicinity of the southwestern Taiwan offshore area. We except to characterize the seismicity in these specific areas in order to better understand the influence of several tectonic structures in the area and its seismogenic characteristics.