Coseismic deformation revealed by inversion of strong motion and GPS data: the 2003 Chengkung earthquake in eastern Taiwan |
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| Authors: | Jyr-Ching Hu Li-Wei Cheng Horng-Yue Chen Yih-Min Wu Jian-Cheng Lee Yue-Gau Chen Kuan-Chuan Lin Ruey-Juin Rau Hao Kuochen Hui-Hsuan Chen Shui-Bei Yu Jacques Angelier |
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| Institution: | Department of Geosciences, National Taiwan University, Taipei, Taiwan. E-mail:;Institute of Earth Sciences, Academia Sinica, Nankang, Taiwan;Central Weather Bureau, Taipei, Taiwan;Department of Earth Sciences, National Cheng Kung University, Tainan, Taiwan;Observatoire Océanologique de Villefranche, Géosciences Azur, Villefranche-sur-Mer, France |
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| Abstract: | A moderate earthquake of M w= 6.8 occurred on 2003 December 10. It ruptured the Chihshang Fault in eastern Taiwan which is the most active segment of the Longitudinal fault as a plate suture fault between the Luzon arc of the Philippine Sea plate and the Eurasian plate. The largest coseismic displacements were 13 cm (horizontal) and 26 cm (vertical). We analyse 40 strong motion and 91 GPS data to model the fault geometry and coseismic dislocations. The most realistic shape of the Chihshang fault surface is listric in type. The dipping angle of the seismic zone is steep (about 60°–70°) at depths shallower than 10 km and then gradually decreases to 40°–50° at depths of 20–30 km. Thus the polygonal elements in Poly3D are well suited for modelling complex surfaces with curving boundaries. Using the strong motion data, the displacement reaches 1.2 m dip-slip on the Chihshang Fault and decreases to 0.1 m near surface. The slip averages 0.34 m, releasing a scalar moment of 1.6E26 dyne-cm. For GPS data, our model reveals that the maximal dislocation is 1.8 m dip-slip. The dislocations decrease to 0.1 m near the surface. The average slip is 0.48 m, giving a scalar moment of 2.2E26 dyne-cm. Regarding post-seismic deformation, a displacements of 0.5 m were observed near the Chihshang Fault, indicating the strain had not been totally released, as a probable result of near-surface locking of the fault zone. |
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| Keywords: | Chengkung earthquake Chihshang fault coseimic deformation Taiwan |
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