Quake follows scientists’ predictions

Seismologists who have been studying the devastation left behind by the Dec. 26 quake and tsunami warned just two weeks ago that another big earthquake was likely to hit the Indian Ocean area. So when an 8.7 magnitude earthquake hit southwest of the Indonesian island of Sumatra on Monday, scientists were quick to spring into action.

Less than an hour after the tremor was recorded at 11:09 a.m. ET, the U.S. National Oceanic and Atmospheric Administration's Pacific Tsunami Warning Center raised the alert. While the Hawaii-based center has no monitoring instruments capable of sensing a tsunami in the Indian Ocean, it called on authorities in the region to "take immediate action."

"This action should include evacuation of coasts within 1,000 kilometers of the epicenter and close monitoring to determine the need for evacuation further away," the advisory said. Alerts were quickly sounded in areas as far away as Thailand and Singapore. In contrast, it took hours after the Dec. 26 earthquake for the tsunami warning to get out, and by that time it was mostly too late.

Quake ranks high
At 8.7 magnitude, Monday's earthquake was roughly half the strength of the December quake, which measured 9.0 on the logarithmic magnitude scale. Monday's event ranked as "one of the largest earthquakes in the past century," said Kerry Sieh, a tsunami researcher at the California Institute of Technology. Additional aftershocks followed Monday's main jolt, said George Choy, a spokesman for the U.S. Geological Survey's National Earthquake Information Center.

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Although scientists cannot predict exactly when seismic events will occur, Monday's quake was not unexpected. In the March 17 issue of the journal Nature, researchers at the University of Ulster-Coleraine in Northern Ireland reported that stress was building in the Sumatran subduction zone as well as in the adjacent Sunda Trench. They warned that the stress was likely to be released in another seismic event.

The faults are part of the Pacific "ring of fire," where continental plates grind against each other and spark periodic seismic shocks. Three months ago, a dramatic shift in the ocean floor along the Sumatra fault set off the waves inundating coastal areas in Indonesia, Thailand, Sri Lanka, India and even as far afield as Somalia.

The Dec. 26 quake set off international calls for better monitoring of Indian Ocean quakes, as well as better plans for emergency response to tsunamis. Officials have been discussing ways to beef up the international tsunami monitoring system, but little action has been taken on that front so far.

"The Indian Ocean still does not have the tide level gauges or the detection buoys that we enjoy in the Pacific," NOAA spokesman Greg Romano told MSNBC.com.

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