1935年新竹-台中 (台湾) 地震のメカニズムと断層モデル

抄録

The Hsinchu-Taichung earthquake (M=7.1) of April 21, 1935 is one of the greatest earthquakes in Taiwan. We analyzed this earthquake using the data of leveling, triangulation, and P-wave first motion. Surface deformation is modeled by a double-fault system in a elastic half-space on the basis of surface traces of the fault. The Hsinchu-Taichung event is a complex one characterized by a strike-slip and a reverse fault. The initial rupture inferred from fault plane solution, is a near vertical right-lateral strike-slip event striking N67°E. A seismic moment of this event is 9×10²⁵dyne·cm. The reverse fault triggered by the initial strike-slip event is the main fault of the Hsinchu-Taichung event with seismic moment of 2.1×10²⁶dyne·cm. An average stress drop is estimated to be about 40 bars. Strike of the reverse fault, N23°E, is consistent with the direction of motion of Philippine Sea Plate. Although tectonics of western Taiwan is a complex one, it may be largely affected by the movement of Philippine Sea Plate.