Wednesday, April 11, 2012

8.6 Magnitude Earthquake Strikes North Sumatra

Analysis by Christina Reed
Wed Apr 11, 2012 07:42 AM ET





UPDATE (7:33 a.m. ET): An aftershock of magnitude 8.2 has struck at 16.4 km (10 miles) deep - at 617 km (383 miles) south southwest of the coast of Banda Aceh. We are continuing to monitor the situation. Follow sea level changes here.

A magnitude 8.6 earthquake struck North Sumatra, Indonesia, at 2:38 p.m. local time today. First estimated as a magnitude 8.7 by the U.S. Geological Survey, the earthquake originated 22.9 km (14.2 miles) below the Earth's crust and struck 434 kilometers (270 miles) southwest of the coast of Banda Aceh, the capital of Indonesia's Aceh province.

NEWS: Hidden Fault Amplified 2004 Tsunami

A tsunami watch and warning was put into effect for the Indian Ocean, immediately after the event. The power is out in Banda Aceh, where residents have moved to high ground, reported Sutopo Purwo Nugroho, a spokesman for the Indonesian National Disaster Management Agency.

The island of Simeulue, Prih Harjadi, and other coastal areas of Aceh are also on alert.

India has taken caution on Andaman and Nicobar Islands, where authorities have ordered people to move out of low-lying areas, CNN reported.

However the geophysics of today's quake do not indicate a repeat of Indonesia's 2004 earthquake is in progress. The magnitude 9.1 earthquake that struck in 2004 and triggered a tsunami that killed more than 200,000 people in 14 countries was a subduction megathrust earthquake closer to shore (250 kilometers south-southeast of Banda Aceh).

Today's temblor appears to have ripped along a transform fault, tearing the seafloor as opposed to popping it apart. Though local tsunami waves are a considerable risk, with calculations showing Simeulue could receive waves as high as 6 meters (20 feet) the widespread tsunami damage seen in 2004 is not anticipated.


IMAGES: Earthquake location map (USGS) Indian Ocean warning in effect (PTWC)

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