Unusually strong strike-slip earthquake

Posted at 5:58 AM, Apr 12, 2012
and last updated 2012-04-12 07:22:00-04

RICHMOND, Va. (WTVR) -The magnitude 8.6 earthquake that affected the Indian Ocean Basin Wednesday April 11, 2012 was of an unusually strong magnitude for a strike-slip type earthquake, according to the United States Geological Survey. However, the USGS states:

"Large strike-slip earthquakes, while rare, are not unprecedented in this region of the Indo-Australian plate. Since the massive M 9.1 earthquake that ruptured a 1300 km long segment of the Sumatran megathrust plate boundary in December of 2004, three large strike-slip events have occurred within 50 km of the April 11, 2012 event. These earthquakes occurred on April 19 2006 (Mw6.2), October 4 2007 (Mw6.2) and January 10, 2012 (Mw7.2). In all three cases, the style of faulting was similar. These events align approximately with fabric of the sea floor in the diffuse boundary zone between the Indian and Australian plates."


The USGS concluded that the April 11, 2012 earthquake 14.2 miles deep underwater was "within the oceanic lithosphere of the Indo-Australia plate. The quake was located approximately 100 km to the southwest of the major subduction zone that defines the plate boundary between the Indo-Australia and Sunda plates offshore Sumatra." (BONUS: Click here to read the full USGS technical report.)

The epicenter of this earthquake was 269 miles southwest of Banda Aceh, Sumatra, Indonesia. Because of the magnitude of this earthquake, a Tsunami Watch was issued for the entire Indian Ocean Basin, then later lifted once it became clear that a dangerous tsunami would not be a threat to land, even though a smaller "significant tsunami" was indicated by tsunami-detecting gauges in the open waters. At this time, there have not been reports of any significant damage, but CBS This Morning reports five deaths are being blamed on the earthquake. Here are all of the reports of people who felt the shaking:


BONUS: Click here for more coverage of the earthquake.

Meteorologist Carrie Rose
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