HR: 15:00h
AN: T13F-06    [Abstracts]
TI: Inversion of Coseimic Deformation of Chengkung Earthquake in Eastern Taiwan Revealed by Strong Motion and Continuous GPS Data
AU: * Cheng, L
EM: r92224106@ntu.edu.tw
AF: National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, Taipei, 106 Taiwan
AU: Lee, J
EM: jclee@earth.sinica.edu.tw
AF: Institute of Earth Sciences, 128 Sec. 2, Academia Rd, Nankang, Taipei 115, Taiwan, Taipei, 115 Taiwan
AU: Wu, Y
EM: drymwu@ntu.edu.tw
AF: National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, Taipei, 106 Taiwan
AU: Lin, K
EM: linkc@scman.cwb.gov.tw
AF: Central Weather Bureau, 64 Gongyuan Rd, Taipei 100,Taiwan, Taipei, 100 Taiwan
AU: HU, J
EM: jchu@ntu.edu.tw
AF: National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan, Taipei, 106 Taiwan
AB: The Mw=6.8 Chengkung Earthquake is almost a pure thrust event which is occurred on Dec. 10th, 2003 in the Costal Range of eastern Taiwan. This earthquake is believed to rupture the NNE-striking Chihshang fault in the Longitudinal Valley. The Chihshang fault is the most active section of the Longitudinal Valley fault, which is a plate suture zone between the Luzon arc of the Philippine Sea plate and the Chinese continental margin of the Eurasian plate. Based on the relocation of aftershock sequences, it is believed that the main shock mainly dislocate the high-angle east dipping Chihshang fault plane. The maximum permanent vertical displacement shown by strong motion data in the hanging wall side is about 18 cm. We analyze 40 strong motion and 6 continuous GPS data around the Chihshang fault to model the fault plane geometry and the distribution of coseismic dislocations. Notably, not only all the stations on the hanging wall of the Chihshang fault were uplifted in this earthquake event, but also the stations on the Longitudinal Valley were still raised till the foothills of the Central Range. Because of the significant uplift on the Longitudinal Valley, we find that the model containing only single Chihshang fault can not well fit the data. Thus we try to investigate the much complex model with an addition subfault plane appended under the Longitudinal Valley. The modeled major Chihshang fault plane exhibits the strike of N20\deg E and dipping of 65\deg S. At the depth of 10 km, the dipping angle declines to 50\deg to the depth of 30 km. For the other subfault connecting to Chihshang fault at depth 10 km, the strike is the same as previous major fault but the dip angle is 50\deg S. Due to this subfault geometry, additional rupture surface will locate at a distance of 3.5 km away from Chihshang fault trace. The predicted coseismic displacements by inversion of the two fault geometry model are much better than that of single fault model, especially around the Longitudinal Valley. The best-fitted model reveals that the maximal dislocation is about 1m dip-slip on the Chihshang fault plane near the hypocenter, and the dislocations near the surface are partly locked declining to 1~10 cm on both fault planes. The calculated scalar moment is 1.9 * 10 $^{26}$ dyne-cm, which is quite compatible with the 2.0 * 10 $^{26}$ dyne-cm based on the data of Harvard CMT.
DE: 7221 Paleoseismology
DE: 7223 Seismic hazard assessment and prediction
DE: 7230 Seismicity and seismotectonics
DE: 8107 Continental neotectonics
DE: 1200 GEODESY AND GRAVITY
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting