Numerical Modeling of the 2004 Sumatra Earthquake Tsunami Based on the Field Survey Data Along the Southwest Coast of Thailand

The 2004 Sumatra Earthquake Tsunami hit the southwest coast of Thailand, which was about 500 km from the tsunami source. Because the area has world famous resorts like Phuket Island and the tsunami hit the coast at around high tide, there was a dreadful tragedy. 5,400 people were killed and 3,100 people reported missing due to the tsunami in Thailand. The author had carried out a field survey in the southwest coast of Thailand a few days after the tsunami. The tsunami heights were 6 to 10 m in Khao Lak, 3 to 6 m in the west coast and 3 m in the east coast of Phuket Island, and 4.5 to 6 m in Phi Phi Islands. Based on the field survey data, the tsunami model has been studied. To begin with, single fault models using CMT solutions by USGS and Harvard University were examined and a model of 84 sub faults 40 km by 70 km referring Yamanaka (2005) was finally suggested. A lot of tsunami energy generated around Nicobar Islands propagated to the southwest coast of Thailand. Then a larger slip dislocation in this region needs to explain the large tsunami in Thailand. Some tsunami models of several rupture velocities have been examined in this study. It has been clear that the rupture velocity had a small effect on the tsunami arriving at the southwest coast of Thailand, because Thailand locates in a perpendicular direction to the rupture propagation direction. The field survey data showed that the tsunami in Khao Lak was much higher than in Phuket Island. It was caused by Similan Islands close to Khao Lak. The tsunami energy trapped in a shallow region around the islands attacked at Khao Lak directly.