Seismogenic Characteristics of the Manila Subduction System, Offshore Southern Taiwan (2)

The southern Taiwan offshore area has been considered to have a low seismic potential in for a long time now. However, based on the historical record from 1900 to the present for the earthquakes with magnitude larger than 7, we observed several events occurred along the Luzon Arc and in its vicinity, around the southern Taiwan. Among them, several earthquakes have caused significant disasters and have been recorded in the literature, for example, the 1936/8/22 ML 7.3 earthquake in the eastern offshore Hengchuen, the 1959/8/15 ML 7.1 earthquake in the SE offshore Hengchuen and the 1996/9/5 magnitude 7.07 earthquake between Hengchuen and Lanyu. In addition, the 1959 Hengchuen earthquake, with an epicenter of about 20 km deep, has induced tsunamis in the southeast and southwest Hengchuen Town area with a wave height of 4 to 5 m and caused many casualties. However, located in the marine area, the acquisition of geological and geophysical data of these area is very difficult, which limits the progress of related research and makes the understanding of the geological structure and the seismogenic mechanism of this area generally insufficient. In order to solve the above mentioned issues, this project aims to study the Manila subduction system by using a temporary ocean bottom seismometer network. By studying the seismic characteristics of these tectonic zones, we attempt to obtain more understanding about the mechanism of the occurrence of large earthquakes, and hope to make a reasonable estimate of the seismic potential and hazards of the southern Taiwan area.