| dc.description.abstract | Recently abundant evidence from geomorphologic and geologic studies has been proposed to identify and to ‘endorse’ an active fault (the Hsincheng fault) which passes through a computer-manufacturing area (the Hsinchu Science Park, HSP) in northern Taiwan. Great public concern has arisen as a consequence. The first substantive proof of the Hsincheng fault was provided by the Chinese Petroleum Corporation (CPC) in 1970’s, based on seismic reflection profiles and borehole data. This fault is no doubt a ‘thrust’ buried below 2 km deep. However, the layers above it seem smoothly and slightly warping, probably due to the ‘thin-skinned’ kind of detachment movement within this deeper ‘blind thrust’. In this paper, we use shallow seismic reflection lines, some co-siting with the CPC lines, to examine the detailed near-surface structure where the fault is expected.
A total of 9 seismic lines across the fault, each about 1 km long and 1.5 km deep, are collected. Among them, three sections at the northern end show fault anomalies: one has an obvious detachment bulge with internal breakages and the other two have fault displacements occurring at shallow depths. However, other sections just show a small buckle vertically presenting in the structure without accompanied breakages. The structural layers are found laid flat without significant offsets at the expected places of the fault. Based on the seismic images, we suggest to lessen the Hsincheng fault as a ‘first-class’ active fault. The fault may have dislocations at deeper places, but the shallow structures are not much affected. These shallow structure variations are restricted to the sallow 400 m depth, which may represent the breakages inside the near-surface thin-skinned layer, which may not have ‘deep’ roots. | en_US |