Location and magnitude of earthquake; map locates epicenter of earthquake in Indonesia. (AP Graphic)

Pacific Rim Bureau—Seven hours after a huge earthquake occurred off the coast of Indonesia, no major tsunami had been reported, but experts did not rule out the possibility of large waves in a region devastated by an earthquake-generated tsunami three months ago.

Measured by the U.S Geological Survey at 8.7 on the Richter scale, the earthquake late Monday night local time was reported to have killed at least 200 people and destroyed around 300 houses on an island named Nias, off Indonesia’s Sumatra.

The earthquake was located several hundred kilometers south-east of the epicenter of the Dec. 26 earthquake, measured at 9.0, which resulted in tsunamis that killed some 270,000 people, most of them in Indonesia, Thailand, Sri Lanka and India.

The Hawaii-based Pacific Tsunami Warning Center earlier urged authorities in the surrounding regions to evacuate coastal inhabitants within 1,000 kilometers (600 miles) of the epicenter.

The Pacific Tsunami Warning Center, which does not have tidal gauges in the Indian Ocean, said it did not know whether large waves had been generated. But it warned that the quake “has the potential to generate a widely destructive tsunami.”

At Australia’s remote Cocos Island, more than 1,000 kilometers south of Sumatra, a 25 centimeter (almost 10 inches) tsunami was recorded. Tsunamis are generally almost indiscernible at sea but can travel thousands of kilometers before rearing up in shallow water approaching coastlines.

Precautionary warnings were issued in surrounding countries, and there were reports of panic in Sumatra, the large Indonesian island where the province of Aceh bore the brunt of the Dec. 26 disaster.

In the aftermath of the December tsunami, the scale of the disaster was not immediately evident, and some critics said the international community did not respond quickly enough.

As the picture became clearer, the U.S. government and military joined Australia and others in providing emergency humanitarian relief as well as pledging continuing aid for reconstruction.

The crisis saw the biggest movement of U.S. military assets in the region since the Vietnam War, as well as the largest ever U.S. and Australian pledges for humanitarian aid.

After news of the latest earthquake broke, the State Department said Monday afternoon it had alerted all of its posts in the region, “putting ourselves in battle mode to be in a position where we can know what’s going on and act appropriately if and when it’s necessary,” according to spokesman Adam Ereli.

“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,” Ereli said.

At 8.7, Monday’s earthquake is one of the eight biggest recorded anywhere since 1900.

According to the University of Edinburgh’s School of Geoscience, the power of earthquakes rises exponentially as the magnitude increases.

While an earthquake measured between 6.0 and 6.9 - of which there are about 120 a year - has the explosive power of a hydrogen bomb (1 megaton), one measured between 7.0-7.9 (18 in the average year) has the power equivalent of approximately 100 hydrogen bombs.

A quake measuring 8.0-8.6, which on average occurs only once every few years, has the explosive power of at least 60,000 hydrogen bombs, it says.