Earthquake off the west coast of northern Sumatra

Tectonic Summary (sources: USGS)

The January 10, 2012 earthquake off the west coast of northern Sumatra, Indonesia, occurred as a result of strike-slip faulting within the oceanic lithosphere of the Indo-Australia plate, 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. At the location of this earthquake, the Indo-Australia plate moves north-northeast with respect to the Sunda plate at a velocity of approximately 52 mm/yr.

While they are rare, large strike-slip earthquakes 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, two Mw 6.2 strike-slip events have occurred within 50 km of the January 10 2012 event, on April 19 2006, and October 4 2007. These events seem to align with fabric of the sea floor in the diffuse boundary zone between the Indian and Australian plates.

Summary

Magnitude	7.3
Date-Time	Tuesday, January 10, 2012 at 18:37:01 UTC Wednesday, January 11, 2012 at 12:37:01 AM at epicenter Time of Earthquake in other Time Zones
Location	2.396°N, 93.175°E
Depth	29.1 km (18.1 miles)
Region	OFF THE WEST COAST OF NORTHERN SUMATRA
Distances	423 km (262 miles) SW of Banda Aceh, Sumatra, Indonesia 537 km (333 miles) SW of Lhokseumawe, Sumatra, Indonesia 951 km (590 miles) W of KUALA LUMPUR, Malaysia 1789 km (1111 miles) WNW of JAKARTA, Java, Indonesia
Location Uncertainty	horizontal +/- 16.3 km (10.1 miles); depth +/- 8.1 km (5.0 miles)
Parameters	NST= 75, Nph= 75, Dmin=504.3 km, Rmss=1.49 sec, Gp= 68°, M-type=regional moment magnitude (Mw), Version=6
Source	Magnitude: USGS NEIC (WDCS-D) Location: USGS NEIC (WDCS-D)
Event ID	usc0007ir5

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Powerful earthquake hits off coast of Indonesia

BANDA ACEH, Indonesia (AP) – A powerful earthquake hit waters off western Indonesia early Wednesday, prompting officials to briefly issue a tsunami warning. Panicked residents poured into the streets, but there were no immediate reports of injuries or serious damage.

The U.S. Geological Survey said the 7.3-magnitude quake struck 260 miles (420 kilometers) off the coast of Aceh province just after midnight. It was centered 18 miles (30 kilometers) beneath the ocean floor.

People in the provincial capital, Banda Aceh— still deeply traumatized by the 2004 monster quake and tsunami — were rattled from their sleep. They fled their homes and waited outside as sirens blared from local mosques, some hopping in cars and motorcycles and heading for high ground.

"I'm afraid," said Fera, a resident, who skidded off on her motorbike with her two children and her mom.

In the town of Seumele, patients were evacuated from a a hospital.

Officials contacted by The Associated Press in several coastal cities, however, had not received any reports about serious injures or damage.

Nearly two hours after the quake struck, the local geological agency lifted it's tsunami warning.

Indonesia is prone to seismic upheaval due to its location on the Pacific "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin.

A giant quake off the country on Dec. 26, 2004, triggered a tsunami in the Indian Ocean that killed 230,000 people, half of them in Aceh.

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