Sunday afternoon's frightning jolt was one of four undersea quakes that struck off the coast the Andaman Islands within a few hours.
The strongest occurred at 2:20 p.m. local time at a depth of only about 6 miles (10 km), according to the U.S. Geological Survey.
The agency said the epicenter was 70 miles (115 km) west-southwest of Port Blair, capital of the Andaman Islands.
Sunday's jolt was the 19th to occur in the same area since April of this year.
Such quakes have become a regular feature of the region since the December 2004 Sumatra quake and resulting tsunami, which caused widespread death and destruction across the Indian Ocean and Bay of Bengal.
The Andaman and Nicobar Islands were at the northern end of the section of seabed that ruptured during that "megathrust" earthquake.
