The Chelungpu Fault is a north-south trending thrust fault in western Taiwan, running along the boundary between the western foothills and the coastal plain. It is one of the principal faults accommodating the intense collision between the Philippine Sea Plate and the Eurasian Plate that is building the mountains of Taiwan.
As a low-angle thrust fault, the Chelungpu carries mountain-front rocks westward and upward over the plain, absorbing part of the rapid crustal shortening across the island. Its trace passes through populated valleys and farmland in the central-western part of the country.
The fault produced the devastating 1999 Chi-Chi earthquake of magnitude 7.6, which killed around 2,400 people and created a dramatic surface rupture more than 80 kilometres long with vertical offsets of several metres in places. The event prompted major scientific drilling projects and made the Chelungpu one of the most intensively studied thrust faults on Earth.