Abstract
The tsunami that accompanied with a magnitude-8 earthquake attacked the Samoan and northern Tongan islands on 29 September 2009. Since the event occured, two scenarios ascertain the mechanism of the earthquake that a series of normal and thrust faults caused the large earthquake and tsunami. However, it is still uncertain which one was the first rupture. In this paper, the authors focus on the tsunami waveforms of Deep-ocean Assessment and Reporting of Tsunamis(DART), and proposed the tsunami source scenario that is the most consistent with the observed tsunami. The scenario is that, the rise time of the thrust fault rupture is 480 seconds, which starts from 3 minutes before the normal fault rupture, and the rise time of the normal fault rupture is 60 seconds.
