M6.6 - SUMBAWA REGION, INDONESIA

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 this 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 the November 8th earthquake, oceanic crust of the Flores Basin subducts to the south along the Flores Thrust.

Earthquakes are fairly common in the region of this event, where 10 events of a similar size to this earthquake have occurred in the last decade. In December 1992, a large M 7.8 earthquake occurred approximately 350 km to the east of this event, causing over 2,500 fatalities and leaving 90,000 homeless both from earthquake shaking effects and from a resulting large tsunami.

Earthquake Information for Asia

Earthquake Information for Indonesia