PI's: Chi-Yuen Wang and Douglas S.Dreger, University of California, Berkeley
Created by oblique collision between the Philippine Sea plate and the Eurasian plate since ~5 Ma, the island of Taiwan is one of the most rapidly rising mountain belts in the world. The 1999 Chi-Chi (Mw=7.6) earthquake, the biggest to hit the island in the last century, has created an unprecedented amount of accurate data and hence a watershed of research opportunity towards a better understanding of earthquake hazards, with a potential to significantly advance the state of knowledge. A timely interpretation of this great amount of data may benefit ongoing programs of earthquake research both in Taiwan and in the US and the other part of the world. Numerical simulation has been widely used for understanding of earthquake hazards. It provides an effective means for testing different models; it may also be used to generate information at locations where data are not available, allowing interpolation between the recording stations. However, recent investigations have shown that the results of such simulation are particularly sensitive to the subsurface structures of the sedimentary basins in the vicinity of the earthquake. Hence, as the first step to a meaningful simulation, the proposed research will focus on defining the 3D structure of the sedimentary basin adjacent to the ruptured Chelungpu fault, using the existing data. The structure so reconstructed will be a pre-requisite for reliable simulations of ground motion and for the detailed study of earthquake source complexity. Finally, the reconstructed basin structure will be useful for other proposed projects and will be made available to the research community. The data required for reconstructing the basin structure in central Taiwan include 3D crustal velocity structure, multi-channel seismic reflection profiles, drilling data and gravity anomalies. The 3D crustal velocity structure has been recently published. Other data have been collected by the Chinese Petroleum Corporation (CPC) as part of its intensive hydrocarbon exploration in this area. The PI visited CPC in December of 1999 and succeeded in getting the collaborative support of Dr. Kuo-An Lin, director of the Exploration and Development Research Institute of CPC, to provide the needed data for the proposed research.