M 7.4 - 102 km SSE of Bengkulu, Indonesia

Tectonic Summary

The February 13, 2001, M 7.4 earthquake just off the southwest coast of the island of Sumatra, one of many islands in the large Indonesian Island Arc system, occurred as the result of shallow reverse faulting. The focal mechanism solutions indicate that rupture occurred on either a steeply dipping reverse fault, or a shallowly dipping thrust fault. At the location of the earthquake, the Australia plate subducts northward beneath the Sunda plate at a velocity of about 62 mm/yr. The boundary is marked by the 3,400-km-long Sunda-Java Trench, about 200 km southeast of the February 13th earthquake. While the focal mechanism solution of this earthquake is consistent with Australia:Sunda subduction, its location and depth indicate that it occurred 15–30 km above the subduction zone interface, in the overriding Sunda plate, perhaps in association with some of the steep accretionary structures mapped in the region. The Australia plate is seismically active to a depth of about 650 km beneath Sumatra and Java.

Because of the earthquake’s depth and proximity to shore it was felt along the coast, but caused little damage. This was not the case for the M 7.9 earthquake in June 2000 that happened less than 60 km west of the February 13th event with similar depth and reverse faulting orientation, which resulted in at least 103 fatalities in the coastal town area of Bengkulu.

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)