Characterization of slip zone associated with the 1999 Taiwan Chi-Chi earthquake: X-ray CT image analyses and microstructural observations of the Taiwan Chelungpu fault

• DOI: 10.1016/j.tecto.2007.12.002
• Publication Date: 2008-02-22T16:36:24Z
• Authors: Tetsuro Hirono; Masumi Sakaguchi; Kenshiro Otsuki; Hiroki Sone; Koichiro Fujimoto; Toshiaki Mishima; Weiren Lin; Wataru Tanikawa; Masaharu Tanimizu; Wonn Soh; En-Chao Yeh; Sheng-Rong Song
• Keywords: Fault gouge; Cataclastic rock

Abstract To characterize the fault-related rocks within the Chelungpu fault, we performed X-ray computed tomography (CT) image analyses and microstructural observations of Hole B core samples from the Taiwan Chelungpu-fault Drilling Project. We identified the slip zone associated with the 1999 Chi-Chi earthquake, within the black gouge zone in the shallowest major fault zone, by comparison with previous reports. The slip zone was characterized by low CT number, cataclastic (or ultracataclastic) texture, and high possibility to have experienced a mechanically fluidized state. Taking these characteristics and previous reports of frictional heating in the slip zone into consideration, we suggested that thermal pressurization was the most likely dynamic weakening mechanism during the earthquake.