Tectonic Summary

The September 13, 2007, M 7.0 earthquake in the Kepulauan Mentawai region of Indonesia occurred as the result of shallow thrust faulting on or near the boundary between the Australia and Sunda plates, and was an aftershock of the M 8.5 and M 7.9 earthquakes that occurred the previous day. At the location of the earthquake, the Australia plate moves northeast with respect to the Sunda plate at a velocity of about 60 mm/yr. The direction of relative plate motion is oblique to the orientation of the plate boundary offshore of the west coast of Sumatra. The component of plate motion perpendicular to the boundary is accommodated by thrust faulting on the offshore plate boundary. Much of the component of plate motion parallel to the plate boundary is accommodated by strike-slip faulting on the Sumatra fault, which is inland of Sumatra proper.

The M 8.5 earthquake of September 12, 2007 is the fourth earthquake with a magnitude greater than 7.9 to occur in the past decade on or near the plate boundaries offshore of western Sumatra. This earthquake occurred just north of the source region of the M 7.9 earthquake on June 4, 2000. The September 13, 2007, M 7.0 earthquake occurred about 320 km northwest of the M 8.5 earthquake and 160 km west of the M 7.9 earthquake, at the northern end of the aftershock zone. This aftershock sequence overlays the southern portion of the estimated 1833 rupture zone, which extends from approximately Enggano Island to the northern portion of Siberut Island. The great-sized M 9.1 earthquake of December 26, 2004, which produced the devastating Indian Ocean tsunami of that date, ruptured much of the boundary separating the India plate and the Burma plate. Immediately to the south of the 2004 earthquake, the M 8.6 Nias Island earthquake of March 28, 2005, ruptured a segment of the plate boundary separating the Australia and Sunda plates. Since the December 26, 2004, earthquake, much of the Sunda Trench between the northern Andaman Islands and Enggano Island, a distance of more than 2,000 km, has ruptured in a series of large subduction zone earthquakes.

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

Tectonic Summary

Historical Magnitude 4.5+ (100km)