According to unofficial estimation, within the 20
century 3.5millions people die in natural disaster, of which over 40% was by earthquakes. Earthquakes remain one of the worst natural disasters posing threats to human civilization. For example on 21 September 1999, an earthquake of magnitude of 7.6 occurred near Chi-Chi Taiwan, causing about 2317 death, 8722 injured, and 51761 buildings collapses [
]. A surface rupture, which is more than 100 km long is associated with the earthquake. The first 90 km surface rupture running roughly followed the known Chelungpu fault in north-south direction, then the surface rupture turned east creating a new fracture zone going through the Shihkang Dam, at where waterfall was formed from a flat riverbed, and the maximum surface displacement of the surface rupture was about 7 m in both vertical and horizontal directions. This newly formed fault arouse much international attention regarding its formation mechanism and many studies are still ongoing. The fault rupture mechanism is still not fully understood. The rupture mechanisms from pre-existing 3-D fault is worth to investigate for it has both academic merit and of societal need.