Seismotectonics of Northernmost Manila Subduction ¡V in Lights of Two OBS Arrays SW offshore Taiwan
Abstract
The Manila trench is well-known as the convergent boundary where the South China Sea plate subducting easternward beneath the Philippine archipelago. As the oblique subduction/collision of plates taken place around the Taiwan area, the topographic feature of the Manila trench lose its topographic identification when approaching northernward to Taiwan. Systematic study for the seismic source parameters along the Manila trench is an important clue to resolve the issue of the complicated plate interaction in the vicinity of northern Manila trench. However, seismological monitoring is largely limited by land territory, where we can readily install established seismometers. In order to compensating the scarcity of earthquake observation at the northern Manila trench, we used Ocean Bottom Seismometer (abbr. OBS) to detect local earthquakes at the relevant area. This study is constructed by two short-period OBS arrays deployed at the offshore SW Taiwan in the years of 2005 and 2006, respectively using 7 and 9 OBS. Local seismic signals have been well logged by the used OBS machines. Thousands earthquakes including micro-events are successfully compiled from these seismograms, and focal mechanisms can be determined by means of near-field waveform simulations or P-wave first-motion polarization for some of the large earthquakes. The preliminary study with these seismic data shows a clear seismicity inclined plane dipping to the northeast at SW Taiwan island. The near-field focal mechanisms reveal apparent convergent forces acting in this area in NW-SE direction. The seismic velocity structure of the relevant region is refined with the OBS records in this study. A clustering algorithm will be applied to relocate earthquakes and consequently to obtain tighter earthquake clouds and thus better-defined seismogenic zone at the northernmost Manila trench.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- Bibcode:
- 2007AGUFM.T51A0314C
- Keywords:
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- 7230 Seismicity and tectonics (1207;
- 1217;
- 1240;
- 1242);
- 7270 Tomography (6982;
- 8180);
- 8123 Dynamics: seismotectonics;
- 8150 Plate boundary: general (3040)