A map showing the population exposure from the M 8.6 earthquake that struck off the west coast of northern Sumatra on April 11, 2012

A magnitude-8.6 earthquake struck off the west coast of northern Sumatra Wednesday, April 11, 2012, at 8:38 a.m., UTC. It was followed by a M-8.2 earthquake at 10:43 a.m. UTC. The estimated depths of these earthquakes are 14 and 10 miles respectively.

The M 8.6 event caused low to moderate shaking in the Sumatran cities of Sinabang and Meulaboh general alarm in costal areas of northwestern Sumatra where people rushed to higher ground. The National Oceanic and Atmospheric Administration issued a tsunami watch for both the M 8.6 and the M 8.2 earthquakes, but subsequently cancelled both.

The current version of the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) estimate is that economic losses are most likely to be less than $1 million range, and there are no expected fatalities.

A map showing the responses to the USGS Did You Feel It? tool following the April 11, 2012 M 8.6 earthquake off the west coast of northern Sumatra

The earthquake struck near the eastern edge of the Indian Ocean off the west coast of northern Sumatra. As of this writing, 1,912 people in 245 cities throughout northern Sumatra and the surrounding region had responded on the USGS Did You Feel It? website.

History of strong earthquakes

Sumatra is located in a tectonically active area, and it experiences frequent significant earthquakes.  In 2004, this area experienced a M 9.1 earthquake that resulted in a significant tsunami. In total, 227,898 people were killed or were missing and presumed dead and about 1.7 million people were displaced by the earthquake and subsequent tsunami in 14 countries in South Asia and East Africa.