Earthquake Locations and Style of Faulting in an Active Arc-Continent Plate Boundary: the Chihshang Fault of Eastern Taiwan
Abstract
The Chihshang fault with a surface slip velocity of 2.2 centimeters per year is the most active segment of the collision boundary between Eurasia and the Luzon arc of the Philippine Sea plate in eastern Taiwan. Albeit its high slip rate, there has not been any significant earthquake occurred along the Chihshang fault since 1951, and the fault now appears to slip with minor earthquakes. Surface deformation of the Chihshang fault is well constrained by detailed geological and geodetic studies, however, the geometry of the fault plane at depth and the style of associated earthquake faulting remain unclear. To obtain a high-resolution fault behavior at depth, we apply the double-difference method to relocate 1040 earthquakes (1.3 < M < 5.4) occurred in the Chihshang area during the period between 1991 and 2000. Statistical re-sampling methods are used to estimate relative location errors. Fault plane solutions for earthquakes with M > 3 are determined by using P-wave polarities and SH/P amplitude ratio. The relocated seismicity defines a narrow SE-dipping inclined fault zone extending from near surface to a depth of 25 km. The middle part of the fault plane has a dip angle of 42° between 10-20 km depth, the dip of the fault plane steepens (72°) upward and flattens (20°) downward. Using bootstrap re-sampling approach, horizontal and depth errors for earthquake locations are typically less than 1.5 and 2 km, respectively. Earthquake focal mechanisms display mainly oblique-reverse faulting with a small strike-slip component. Our study offers fine-scale fault plane geometry and style of earthquake faulting for the Chihshang fault, which are important for earthquake hazard assessment in eastern Taiwan.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.T61B1277C
- Keywords:
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- 7215 Earthquake parameters;
- 7230 Seismicity and seismotectonics;
- 8015 Local crustal structure;
- 8123 Dynamics;
- seismotectonics;
- 8164 Stresses: crust and lithosphere