Magnitude 6.6 struck South Sumatra region on Thursday, October 01, 2009 at 08:52:29 AM local time. The epicenter located 270 km southeast of the damaging M 7.6 earthquake of September 30, 2009 offshore Padang at position 2.589°S, 101.546°E. It is not clear at present if these events are related but there is a big possibility that the Padang earthquake triggering the October 1st earthquake. Hundreds buildings collapse while fatalities are not reported yet but expected to rise.
According to USGS, the October 1st, 2009 Mw6.6 earthquake in southern Sumatra occurred as a result of shallow strike-slip faulting within the Sunda Plate. In the epicentral region of this earthquake, the Australian plate moves northwestwards with respect to the Sunda Plate at a rate of approximately 65 mm/yr. Oblique convergence at the trench, to the west of this earthquake, is partitioned between thrust motion on the subduction zone interface and strike-slip motion in the upper plate, near the Sumatra Fault. Todays earthquake is likely related to the latter strike-slip component of this motion, accommodating the northward motion of the Sunda block with respect to the interior of the Eurasian Plate. On the basis of the currently available fault mechanism information and a depth of 15 km, it is likely that this earthquake occurred along the Sumatran Fault or on a closely related structure. The recent earthquake is consistent with NW-directed, right-lateral displacement along the Sumatran Fault system.