HR: 1340h
AN: T13A-1353    [Abstracts]
TI: Dynamics of Chi-Chi earthquake rupture: Discovery from Seismological Modeling and Taiwan Chelungpu-fault Drilling Project (TCDP)
AU: * Ma, K
EM: fong@earth.ncu.edu.tw
AF: Institute of Geophysics, National Central Univ., 300 Jungda Rd., Chung-Li, TWN 320-54 Taiwan
AU: Wang, C
EM: wangcy@cc.ncu.edu.tw
AF: Institute of Geophysics, National Central Univ., 300 Jungda Rd., Chung-Li, TWN 320-54 Taiwan
AU: Hung, J
EM: jhung@earth.ncu.edu.tw
AF: Institute of Geophysics, National Central Univ., 300 Jungda Rd., Chung-Li, TWN 320-54 Taiwan
AU: Song, S
EM: srsong@ntu.edu.tw
AF: Department of Geological Sciences, National Taiwan Univ., Taipei, TWN 100 Taiwan
AU: Tanaka, H
AF: Tokyo Univ., Tokyo Univ., Tokyo, 113 Japan
AU: Yeh, E
EM: yeh@jamstec.go.jp
AF: JAMSTEC, JAMSTEC, Tsukuba, 113 Japan
AU: Tsai, Y
EM: ybtsai@earth.ncu.edu.tw
AF: Institute of Geophysics, National Central Univ., 300 Jungda Rd., Chung-Li, TWN 320-54 Taiwan
AB: Taiwan Chelungpu-fault Drilling Project (TCDP) for understanding earthquake physics for a large slip was commenced in Feb., 2004. This project plans to continue coring from the depth of 500 m to 2000 m. The drilling was expected to hit the Chelungpu fault, which ruptured during the 1999 Chi-Chi, Taiwan, earthquake, at around 1000 m. In Aug., 2004, the drilling came to the ChinShui Shale formation around 1025 m to 1300m. Several possible fault zones were identified at the depths of 1111, 1153, 1222, and 1241m. As identified by on-site geologists from the geometry and setting of the fault zone, the depth at 1111m is the most possible fault zone associated with the recent ruptured Chi-Chi earthquake. The identified fault zone has a dip angle of about 20 degree with slip direction of 70 degree, consistent with the value obtained from kinematic waveform inversion for spatial slip distribution. The identified fault zone from the core shows a thickness of about 2-4 cm. Although detail experiment on the core is necessary for further justification, several dynamic parameters can be estimated at the first hand. Considering the amount of slip at the slip zone of 8m in dip direction of 30 degree, the scale of the slip thickness to the final slip is in the scale of 0.5-1x10-2. It yields the temperature rise due to fault slip to a value of about 400-800C for initial stress of 100 bars. If we consider a total release of stress drop of 300 bars obtained from dynamic modeling as the initial stress, the temperature rise for this event will be up to 1200-2400C. For the high temperature, possible fluid pressure, melting and lubrication could take place in the fault zone. These dynamic processes can be further justified from experiments on core. Other further parameters as fracture energy and scaled energy of this event can be also derived through the direct evidence of the core. These numbers can be compared with the dynamic waveform modeling results. The TCDP, indeed, provides the unique opportunity to really see the recent ruptured slip zone to confirm the hypothesis on rupture behavior of faulting.
DE: 7200 SEISMOLOGY
DE: 7209 Earthquake dynamics and mechanics
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting