An Interpretation of the 1999 Chi-Chi Earthquake in Taiwan Based on the Thin-Skinned Thrust Model

The 1999 Chi-Chi earthqqake (ML =7.3) which occurred in central Taiwan marks the island's largest inland seismic event of the twentieth cen tury. The Chi-Chi earthquake had three notable characteristics: 1) its source depth was very shallow (8 km), with aftershocks distributed in a semi-cir cular belt surrounding the Peikang basement high; 2) it triggered a 90 km long, north-south trending, active fault (the Chelungpu fault), mostly of the thrust type. Its hanging wall side suffered much larger distortions than the foot wall side; and 3) the fault trace bent toward the northeast at its north ern tip 50 km away from the source, where the largest surface rupture occurred (9.8 m).