An earthquake measuring 8.7 on the Richter scale shook the coastal regions of the Indian Ocean Monday at 10:09 a.m. CST, and officials were concerned another tsunami would occur.

Whether an earthquake produces a tsunami is determined by three factors, said NIU staff meteorologist Gilbert Sebenste. These factors are if the earthquake has a 7.5 intensity or greater, occurs over a large body of water such as a sea or an ocean and the center of the quake is close to the surface of the earth.

“All three were met with this earthquake,” Sebenste said. “It does not guarantee a tsunami because it also depends on local underwater terrain. If the area of the ocean was deep where the earthquake occurred, it has a better chance of producing a tsunami.”

Any earthquake with a magnitude exceeding 8.0, regardless of the terrain, can produce a major tsunami, Sebenste said.

The Dec. 26 tsunami measured 9.0 on the Richter scale, killing at least 175,000 people. While the U.S. Geological Survey initially addressed Monday’s earthquake at magnitude 8.2, it was later upgraded to an 8.7.

“With earthquakes this strong the initial intensity is likely to be underestimated, at least somewhat,” Sebenste said.

Because the threatened area does not have tsunami detection equipment, U.S. officials frantically called over to alert people, Sebenste said.

“Indonesia, Sri Lanka and Thailand have ordered evacuations off the coastline,” Sebenste said.

The National Oceanic and Atmospheric Administration encouraged anyone within 1,000 kilometers of the epicenter to immediately evacuate the area.