Slip distribution on a thrust fault at a plate boundary: the 2003 Chengkung earthquake, Taiwan

Abstract

The 2003 Chengkung earthquake (Mw 6.8) occurred on the east-dipping Chihshang fault of eastern Taiwan, a listric fault with dominant reverse motion. A joint inversion taking into account geodetic (GPS) and seismological (accelerometric and teleseismic) data is performed. This modelling highlights the rupture process behaviour on the fault plane at depth. The coseismic rupture developed essentially between 12 and 26 km depth, expanding laterally by about 30 km towards the SSW. Two slip patches dominated, with slip values exceeding 1.5 m. During the 30 s of the whole process, the rupture propagation decelerated with time, starting at 3.4 ± 0.3 km s−1 in the two main slip patches and ending with velocities below 1.6 ± 0.1 km s−1. The 48 hr of aftershocks that followed the main shock are distributed essentially inside the coseismic slip patches on the fault surface, except in the deepest, southern part of the fault where slip is less resolved. The results of our modelling illustrate the particular behaviour of the 2003 Chengkung earthquake where the coseismic slip rapidly diminished towards the surface, in good agreement with the observation of fast post-seismic slip followed by interseismic creep along the Chihshang fault.