- © 2005 by the Seismological Society of America
The epicenter of the Mw 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 (Grünthal, 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.
This study focuses on evidence for shaking intensity resulting from the earthquake, ignoring damage due to the tsunami, landslides, or liquefaction. Preliminary ground-based tsunami surveys are available (Borrero, 2005; NICEE, 2005); these provide some information about shaking intensities as well but are spatially limited. First-hand accounts of the disaster and damage reports that appeared in Web logs, conventional newspapers, and Web sites are evaluated along with 48 felt reports sent via the Internet by eyewitnesses in India. Multiple felt reports were received from places such as Bhubaneswar, Chennai, and Port Blair. The highest assigned intensity of 9 EMS was reported from Lameureum, on the northwest coast …