The U.S. Geological Survey has upgraded today's earthquake off the coast of Indonesia from 8.2 to 8.7.

So far, about 50 deaths have been reported on the island of Nias, near the quake's epicenter.

A tidal gauge detected a "small" tsunami in the Indian Ocean several hundred miles southwest of the quake, but the actual size of the wave is unclear. The tsunami threat for Indonesia and Thailand has likely passed, since waves would have reached those countries almost immediately. Warnings are still in effect for Malaysia, Sri Lanka, and Sumatra, however.

Today's earthquake involves the same fault as the December 26 quake. However, the energy from this one was probably directed south of the areas hardest hit in December. Robert Cessaro, of the Pacific Tsunami Warning Center, says:

"So all that pressure to the north would have been relieved [by the December 26 quake]. We think this event probably ruptured to the south, with the beam of energy probably propagated to the south toward Mauritius and the Rodrigues."

The U.S. State Department says that U.S. posts in the region have been alerted and are reaching out to aid workers. Spokesman Adam Ereli said:

"We're applying what we've learned from the previous earthquake, so that we can be prepared to be responsive quickly and in a meaningful way."