The influence of surface ruptures on building damage in the 1999 Chi-Chi earthquake: a case study in Fengyuan City J.J. Dong a, * , C.D. Wang b , C.T. Lee a , J.J. Liao c , Y.W. Pan c a Institute of Applied Geology, National Central University, No. 300, Jungda Road, Jungli City, Taoyuan 320, Taiwan, ROC b Department of Civil Engineering, Nanya Institute of Technology, Jungli, Taiwan, ROC c Department of Civil Engineering and Hazard Mitigation Research Center, National Chiao-Tung University, Hsinchu, Taiwan, ROC Abstract In addition to the main surface rupture along the Chelungpu fault associated with the 1999 Chi-Chi, Taiwan earthquake, numerous secondary or branch ruptures on hangingwall were also observed. These secondary surface ruptures are parallel or sub-parallel to the main rupture within a distance of a few meters to 1 – 2 km. The rupture length of these secondary ruptures varies from a few tens of meters up to 5 km. The surface deformation resulted in serious damages of buildings. The present work studied the features of surface deformation on the hangingwall around the Chung-Cheng Park, Fengyuan, Taichung. Three distinct surface ruptures, minor ruptures and tension cracks were observed in this area. The observed distribution and types of building damage on the hangingwall are demonstrated. Due to the difference in geological condition and complex pattern of surface deformation, the resulted building damages on the hangingwall vary. A series of site investigation including field survey, drilling, seismic prospecting, P–S logging tests and laboratory tests were carried out in the interested area. A geological structure model was proposed on the basis of the results of site investigation. Numerical simulation was carried out to model the surface deformation as well as subsurface potential damage zone of an active fault. It reasonably explains the observed pattern of surface deformation and indicates that the surface deformation zone during a catastrophic earthquake is predictable. D 2003 Elsevier Science B.V. All rights reserved. Keywords: Hangingwall; Building damage; Chi-Chi earthquake 1. Introduction The 1999 Chi-Chi earthquake (M w 7.6) resulted in more than 2000 casualties and numerous damages in various structures and buildings. Among many dam- ages of buildings, lots of them are due to the in- fluence of surface ruptures associated with the catastrophic earthquake. The surface ruptures include main surface rupture, as well as secondary or branch ruptures which were observed on the hangingwall, within a few meters to 1–2 km, and parallel or sub- parallel to the main rupture. The rupture length of these secondary ruptures varies from a few tens of meters up to 5 km. Bonilla (1970) found that dis- placement on secondary fractures could be as much as 20% that on the main fault even if they are 12 km away. Hence, the potential for the displacement of 0013-7952/$ - see front matter D 2003 Elsevier Science B.V. All rights reserved. doi:10.1016/S0013-7952(03)00131-5 * Corresponding author. Tel.: +886-3-4224114; fax: +886-3- 4263127. E-mail address: jjdong@geo.ncu.edu.tw (J.J. Dong). www.elsevier.com/locate/enggeo Engineering Geology 71 (2003) 157 – 179