Subsurface Structure, Physical Properties, and Fault Zone Characteristics in the Scientific Drill Holes of Taiwan Chelungpu-Fault Drilling Project

• Main Authors: Jih-Hao Hung, Yun-Hao Wu, En-Chao Yeh, Jong-Chang Wu, TCDP Scientific Party
• Format: Article
• Language: English
• Published: Chinese Geoscience Union 2007-01-01
• Series: Terrestrial, Atmospheric and Oceanic Sciences
• Subjects: Chi-Chi earthquake; Taiwan Chelungpu-fault Drilling Project; Fault-zone fabrics; S-wave anisotropy
• Online Access: http://tao.cgu.org.tw/images/attachments/v182p271.pdf

Continuous coring and a suite of geophysical measurements were collected in two scientific holes to understand physical mechanisms involved in large displacements in the 1999 Chi-Chi earthquake. Physical properties of formations obtained from wire-line logs including P- and S-wave sonic velocity, gamma ray, electrical resistivity, density and temperature, are primarily dependent on parameters such as lithology, depth and fault zones. The average dip of bedding, identified from both cores and FMI (or FMS) logs, is about 30 degrees towards the SE. Nevertheless, local azimuthal variations and increasing or decreasing bedding dips appear across fault zones. A prominent increase in structural dip to 60¢X_n- 80¢X_nbelow 1856 m could be due to deformation associated with propagation of the Sanyi fault.