M 7.3 - Near the south coast of Papua, Indonesia

Tectonic Summary

The February 7, 2004, 7.3 Papua, Indonesia earthquake occurred as a result of shallow strike-slip faulting on or near the plate boundary separating the Australia and Sunda plates. Focal mechanism solutions indicate that rupture occurred on either a left-lateral east-west oriented fault or a right-lateral fault trending north-south. The earthquake lies near the boundary between the Birds Head and the Maoke microplates, an east-northeast trending boundary that accommodates approximately 80 mm/yr of left-lateral motion. While slightly oblique to this orientation, the east-west plane of the focal mechanism solution is more consistent with motion along this plate boundary. Eastern Indonesia is broadly characterized by complex tectonics in which motions of numerous small microplates are accommodating large-scale convergence among the Australia, Pacific, Philippine Sea, and Sunda plates. The interactions among these microplates produce all possible styles of faulting.

Eastern Indonesia has experienced many strong earthquakes. Since 1979, the region within 300 km of the mainshock of the February 7th earthquake has experienced four other earthquakes with magnitudes greater than 7, the largest of which was a M 7.9 event in September 1979. The earthquake closest to the February 7th event was the damaging M 7.0 event 2 days earlier, approximately 60 km to the northeast, which resulted in almost 40 casualties and significant damage to housing and local infrastructure.

Hayes et al. (2016) Tectonic summaries of magnitude 7 and greater earthquakes from 2000 to 2015, USGS Open-File Report 2016-1192. (5.2 MB PDF)