Magnitude 7.3 - NICOBAR ISLANDS, INDIA REGION

Earthquake Summary

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Felt Reports

Some buildings damaged in the Andaman and Nicobar Islands. Felt (V) on Car Nicobar, Katchal and Nancowry. Also felt (V) at Campbell Bay, Great Nicobar and Port Blair, South Andaman Island. Felt (IV) at Chennai; (III) at Srikakulam, Visakhapatnam, Vizianagaram and other coastal areas of Andhra Pradesh and at Dum Dum and Garia, West Bengal, India. Felt at Mamallapuram, India. Felt (IV) in Aceh Province, Indonesia. Felt (III) at Colombo, Matale and Kandy, Sri Lanka. Felt at Peraliya and Sri Jayawardenepura Kotte, Sri Lanka. Also felt at Male, Maldives and on Phuket, Thailand.

Tectonic Summary

This earthquake occurred near the western boundary of the aftershock zone of the devastating Sumatra-Andaman Islands earthquake of December 26, 2004. The aftershock zone of the December 26th earthquake continues to be active and forms a crescent-shaped region extending about 1200 km north of Sumatra, Indonesia. The recent event was a strike-slip earthquake, probably in the India plate below its shallowly dipping boundary with the Burma plate. The earthquake resulted from horizontal displacement of the ground across a nearly vertical fault plane. This is unlike the thrust-fault motion that produced the December 26th earthquake and that occurred on the interface of the eastward-subducting India plate and the overriding Burma plate. The recent event therefore occurred on a different fault than the fault that caused the Great Sumatra-Andaman Islands earthquake. However, the two earthquakes are almost certainly related. A great earthquake can trigger earthquake activity on faults that are distinct from the main-shock fault plane, and separated from it by tens or even hundreds of kilometers. A magnitude 7.2 earthquake is considered a major earthquake, but the size of this recent earthquake pales in comparison to the December 26th earthquake. A 7.2 strike-slip earthquake typically ruptures a 15 km by 80 km patch along a fault, whereas the December 26, 2004 earthquake ruptured a patch of fault about 1200 km long and 200 km wide.

Earthquake Information for INDIA

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Tsunami Information

The earthquake locations and magnitudes cited in NOAA tsunami statements and bulletins are preliminary and are superseded by USGS locations and magnitudes computed using more extensive data sets.

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Additional Information

• News Release
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