Study on the Tectonic Structures between the Northern Manila Trench and the Passive Continental Margin(2/2)

The deformation front (DF) off SW Taiwan is the northward extension of theManila Trench and is also located in the nethermost portion of the South China Sea (SCS).To the east of the DF, it is an active continental margin where the SCS lithospheresubducts beneath the Luzon Arc, while to the west of the DF it the passive continentalmargin of the northern SCS. Thus, the transition zone is complicated and separates thethrusts and folds to the east from the normal faults to the west. In fact, the exact trace ofthe DF was never been well defined. However, the frontal thrust abutting the DF issimilar to the Chelungpu Fault in middle Taiwan that occurred an earthquake ofmagnitude 7.3. In the case of frontal thrust, it may generate large earthquake as well aslarge tsunami and jeopardize the south Taiwan. On the other hand, a long and SE dippingnormal fault in the passive continental margin may cause a large submarine landslide andtsunami. In that case, a large tsunami also threatens the south Taiwan. Although thegeology of continental margin in southernmost SCS involves the initial continentalbreakup, it was never been studied in details. Thus, we expect to collect and analyzemarine geophysical data to better understand the geological structures of both the passiveand the active continental margin of the northernmost SCS in 3 years. Especially we willuse multi-beam bathymetry to study the morphological features and use seismic reflectionprofiles to understand the deep structures. Our results can also help us estimate potentiallarge earthquakes and tsunamis in the northernmost SCS.