- © 2005 by the Seismological Society of America
The great Sumatra-Andaman earthquake of 26 December 2004 is the most extensively recorded Mw > 9.0 event in history. It also occurred in the modern era of broadband digital seismometry and advanced communication systems. For these reasons, the event offers hitherto unequaled opportunity for detailed studies of a great, destructive tsunami earthquake. As discussed by Park et al. (2005a), the global seismographic network performed well and met the challenge posed by the event. Indeed, due to the availability of high-quality data in near real-time, a free flow of information among scientists, and the importance of the event, many studies of this earthquake have quickly become available.
The rupture during the Sumatra-Andaman earthquake initiated at 3.3°N 96.0°E and propagated northward for a length of 1,200 to 1,300 km with an average speed of 2.5 to 2.8 km/s (e.g, Ammon et al., 2005; Ishii el al., 2005; Ni et al., 2005). The Harvard CMT solution, based on a dominant period of ∼400 s (G. Ekström, personal communication, 2005), gives a seismic moment of 4.0 × 1022 N-m (Mw 9.0). Analyses of free oscillation data reveal an increase in the moment rate spectrum with increasing period up to 3,000 s (Park et al., 2005b; Stein and Okal, 2005). These studies are based on the longest-period normal modes of the Earth, 0S2 and 0S3, excited by the earthquake. The estimated M0 at the period of 3,000 s differs between the two studies: 1.0 × 1023 N-m (Mw 9.3) by Stein and Okal (2005), and 6.5 × 1022 N-m (Mw 9.1) by Park et al. (2005b). Henceforth, we will use Mw 9.0 for the earthquake.
Inversion of slip on the fault using teleseismic …