Poster of the Offshore Padang, Sumatra, Indonesia Earthquake of 25 February 2008 - Magnitude 7.2

Tectonic Summary

The magnitude 7.2 Kepulauan Mentawai, Indonesia, earthquake of February 25, 2008 occurred as the result of thrust faulting on the boundary between the Australia and Sunda plates. At the location of this earthquake, the Australia plate moves north-northeast with respect to the Sunda plate at a velocity of about 60 mm/year. 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, with the Australia plate subducting beneath the Sunda plate. Much of the component of plate motion parallel to the plate boundary is accommodated by strike-skip faulting on the Sumatra fault, which is inland on Sumatra proper.

This earthquake continues an episode of unusually high earthquake activity that has impacted Sumatra and vicinity in recent years. Previous earthquakes in the series of shocks include the Sumatra-Andaman Islands earthquake of December 26, 2004 (M 9.1), the Nias earthquake of March 28, 2005 (M 8.6), and the southern Sumatra earthquakes of September 12, 2007 (M 8.4 and 7.9). The earthquake of February 25, 2008, occurred within the broad section of the Sumatra subduction zone that was spanned by aftershocks of the southern Sumatra earthquakes of September 12, 2007.

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