Powerful magnitude-7.8 earthquake in Indonesia

The earthquake struck off on Wednesday 15 miles deep on coast of Sumatra island; "no tsunami observed"

The quake epicenter was 15 miles deep in the Indian Ocean, 410 miles southwest of Muara Siberut and 500 miles west-southwest of Padang, as indicated by the U.S. Geological Survey. After an initial tsunami threat, the warning was lifted at 10:50 p.m. on Wednesday, after no tsunami was observed on the islands of Sumatra, West Sumatra, Bengkulu and Lampung.

Nevertheless, Australia's Bureau of Meteorology issued "dangerous rips, waves and strong ocean currents” warnings for Cocos Island and Christmas Island.

No casualties or damage were reported so far.

Ring of Fire - brief earthquake history

Frequent earthquake and volcanic eruptions activity is common in the Ring of Fire in the Pacific Basin, all around Indonesia.

A magnitude-9.1 earthquake in December 2004 hit the west coast of Northern Sumatra, striking with an energy equal to a 100-gigatone bomb. The generated tsunami waves killed 225.000 people.

In March 2005 and May 2006, another two earthquakes of magnitude-8.7 and 6.3 respectively have killed more than 7.000 people in the region.