Coseismic versus interseismic ground deformations, fault rupture inversion and segmentation revealed by 2003 <i>Mw</i> 6.8 Chengkung earthquake in eastern Taiwan

Abstract

The 2003 Chengkung earthquake ( Mw 6.8) provided diagnostic evidence for a source model showing the deformation process of the seismogenic Chihshang fault in eastern Taiwan. The aftershocks show a fault‐bend at a depth of 18 km. Coseismic ground displacements recorded by strong‐motion records allow us to deduce instant rupturing of this event. Our resulting model shows a fault length of ∼33 km and dip‐slip dominant rupture on fault‐plane deeper than 18 km. Estimated coseismic displacements constrain two fault planes: one at 5–18 km depth dipping 60°E and 18–36 km depth dipping 45°E. The uppermost fault‐plane of the Chihshang Fault (0–5 km) did not break immediately after the main shock; however, it may have a major role in after‐slip and even interseismic ground deformation. The Taiyuan basin developed in the hanging wall is a geomorphic feature consistent with and adequately explained by coseismic ground displacements.