Poster of the Sumbawa, Indonesia Earthquake of 08 November 2009 - Magnitude 6.7

Tectonic Summary

The November 8th, 2009 earthquake in the Sumbawa region of Indonesia occurred as a result of thrust faulting on or near a microplate boundary within the Sunda plate. Eastern Indonesia is characterized by complex tectonics in which motions of numerous small plates are accommodating large-scale convergence between the Australian and Sunda plates. In the region of today's earthquake, the Australian plate moves northeastwards with respect to the Sunda plate at a rate of approximately 75 mm/yr. The convergence across this plate boundary has caused two oppositely oriented thrust zones; in the south, Australian plate subducts beneath Sunda towards the north at the Java Trench, while on the northern side of the eastern Sunda Arc near the location of November 8th's earthquake, oceanic crust of the Flores Basin subducts to the south along the Flores Thrust.

Earthquakes occur frequently in the region of Sumbawa. In December 1992, a large M7.8 earthquake occurred approximately 350 km to the east of the November 8 event. The 1992 shock and associated tsunami caused over 2,500 fatalities and leaving 90,000 homeless.