Intensity distribution from the 2004 M 9.0 Sumatra-Andaman earthquake

The epicenter of the M(W)9.0 Sumatra-Andaman earthquake on 26 December 2004 at 00:58 UTC occurred near the northwestern end of Sumatra and ruptured northward along the Andaman and Nicobar Archipelago (Figure 1). The principal rupture had a duration of more than 10 minutes (Park et al., 2005) and was perceptible to a distance of 3,300 km westward and 2,600 km northward. The largest accelerations were perceived near the epicenter, but high intensities were also perceived along the archipelago with diminishing intensity northward. Presented here are 206 intensity reports interpreted in terms of EMS-98 (Grunthal, 1998), a scale with similarities to the MSK and Modified Mercalli Intensity scales but designed to take into account modern building practices. The data are culled from primary accounts, newspaper reports, and responses to an online intensity questionnaire (http://asc-india.org/menu/felt.htm). Insofar as additional epicentral data will be forthcoming in the next several months, the data are presented with a minimum of interpretation.