[S-SS04] Seismological advances in the ocean

[SSS04-P05] Earthquake activity in Manila subduction zone off the western Luzon Island : Experience and preliminary results with the Ocean Bottom Seismometer

*Shiou-Ya Wang¹、Shu-Kun Hsu²、Wen-Nan Wu²、Chin-Wei Liang¹、Lien-Kai Lin² (1.Center for Environmental Studies, National Central University, Taiwan、2.Department of Earth Sciences, National Central University, Taiwan)

キーワード：Seismogenic structure, Manila subduction zone, Ocean Bottom Seismometer

The Philippine lies along the Pacific Ring of Fire, which is one of the most earthquake prone countries in the world. The complex active tectonic and geologic setting of Philippine is attributed to the place interaction along the surrounding subduction zone. In this work, we are focus on investigating the earthquake activity and tectonic beneath the Manila subduction zone off western Luzon Island. Although there are few earthquakes of magnitude 7 or greater in past 100 year along the Marnila subduction zone in the Luzon Island section, we still cannot underestimate earthquake risk. Indeed, a large earthquake with Mw7.9 generate on 14 February 1934 near the Manila Trench. This event took place in the vicinity of the event occur on 29 August 1977, which generated a small tsunami on the nearby coast of Luzon. For this situation. However, due to land seismic observations suffer particularly from insufficient azimuthal coverage and earthquake detection capacity causing lack of offshore earthquakes data. Therefore, it’s difficult to describe detail structure and seismic potential of Manila subduction zone. This study aims to improve our knowledge of study area, the Ocean Bottom Seismometer play an key role, which is developed for recording seismic wave caused by tectonic activity in the sea. A temporary Broadband Ocean Bottom network with 11 OBSs has been deployed from March, 2020 and retrieved for 1 year long waveform data. By combining the data from OBS stations with that of existing land-based stations, we were able to detected and accurately located the seismic activity around study area.In this report, we present the first detailed seismic activity of study area. We also discuss seismotectonic interpretations based on new marine earthquake data. We expect these results can provide us with a new insight of geological development of Manila subduction zone.