title: Slip zone and energetics of a large earthquake from the Taiwan Chelungpu-fault Drilling Project.
abstract: Determining the seismic fracture energy during an earthquake and understanding the associated creation and development of a fault zone requires a combination of both seismological and geological field data. The actual thickness of the zone that slips during the rupture of a large earthquake is not known and is a key seismological parameter in understanding energy dissipation, rupture processes and seismic efficiency. The 1999 magnitude-7.7 earthquake in Chi-Chi, Taiwan, produced large slip (8 to 10 metres) at or near the surface, which is accessible to borehole drilling and provides a rare opportunity to sample a fault that had large slip in a recent earthquake. Here we present the retrieved cores from the Taiwan Chelungpu-fault Drilling Project and identify the main slip zone associated with the Chi-Chi earthquake. The surface fracture energy estimated from grain sizes in the gouge zone of the fault sample was directly compared to the seismic fracture energy determined from near-field seismic data. From the comparison, the contribution of gouge surface energy to the earthquake breakdown work is quantified to be 6 per cent.
authors.affiliation: Department of Earth Sciences, National Central University, Chung-Li 32054, Taiwan. fong@earth.ncu.edu.tw
authors.forename: Kuo-Fong
authors.initials: KF
authors.lastname: Ma
authors.forename: Hidemi
authors.initials: H
authors.lastname: Tanaka
authors.forename: Sheng-Rong
authors.initials: SR
authors.lastname: Song
authors.forename: Chien-Ying
authors.initials: CY
authors.lastname: Wang
authors.forename: Jih-Hao
authors.initials: JH
authors.lastname: Hung
authors.forename: Yi-Ben
authors.initials: YB
authors.lastname: Tsai
authors.forename: Jim
authors.initials: J
authors.lastname: Mori
authors.forename: Yen-Fang
authors.initials: YF
authors.lastname: Song
authors.forename: Eh-Chao
authors.initials: EC
authors.lastname: Yeh
authors.forename: Wonn
authors.initials: W
authors.lastname: Soh
authors.forename: Hiroki
authors.initials: H
authors.lastname: Sone
authors.forename: Li-Wei
authors.initials: LW
authors.lastname: Kuo
authors.forename: Hung-Yu
authors.initials: HY
authors.lastname: Wu