Tectonic Summary

The September 29, 2010, M 7.0 earthquake near the south coast of Papua, Indonesia, occurred as a result of shallow normal faulting along a section of the broad plate boundary system in eastern Indonesia to the northwest of the Aru Islands. Focal mechanism solutions indicate that rupture occurred on either a north- or south-striking, moderately dipping normal fault.

Eastern Indonesia is characterized by complex tectonics in which motions of numerous small plates are accommodating large-scale convergence among the Australia, Sunda, Pacific, and Philippine Sea plates. The September 29th earthquake lies near the boundary between the proposed Banda Sea microplate and the Australia plate proper, which is oriented approximately north-northeast and accommodates divergent motion between these plates. The focal mechanism solution of the earthquake is consistent with its occurrence on such a boundary, though due to the complexity of tectonics in this region, any specific association with a causative fault structure must be regarded as speculative, pending further study. At a broad scale, the Australia plate moves northward with respect to the Sunda plate at a velocity of approximately 77 mm/yr in the region of the earthquake. In more detail, it has been estimated that the Banda Sea microplate moves westward with respect to the Australia plate at a velocity of about 15 mm/yr.

The September 29th earthquake was preceded approximately 27 seconds earlier by a smaller, M 6.2 event, from nearly the same epicenter. Eastern Indonesia is a tectonically active area with frequent moderate and large earthquakes. The region within 300 km of the September 29th event experienced more than 30 earthquakes larger than M 6 in the past half century.

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)

Event Details

Event Map

Tectonic Summary

Historical Magnitude 4.5+ (100km)

Tectonic Summary

Historical Magnitude 4.5+ (100km)