The 1999 Chi‐Chi earthquake (Mw 7.6) was due to slip along the Chelungpu fault: a major N striking thrust fault in the fold‐thrust belt of western Taiwan. The surface rupture extends over 100 km in a N‐S trend with NW trending horizontal displacement increasing from 2 to 10 m from south to north. The slip azimuths progressively rotate from north/northwest in the north to west southwest in the south.
During the Chi-Chi earthquake most of the damage concentrates on nearly surface rupture. In this talk we will review the detail surface deformation especially near the surface rupture to discuss the surface deformation and how it is related with building damages. We also will discuss the mechanism of controlling the length of the Chelungpu fault and we conclude the magnitude of the Chelungpu fault is largest western Taiwan.