Powerful earthquake, small tsunamis hit Indonesia

October 26th, 2010 - 12:58 am ICT by BNO News  

JAKARTA (BNO NEWS) — A small tsunami was recorded after a powerful earthquake struck off the western coast of Sumatra, officials said, but there were no immediate reports of casualties.

The 7.2-magnitude earthquake at 9.42 p.m. local time (1442 GMT) was centered just off the Mentawai Islands, about 240 kilometers (149 miles) south of Padang, the capital and largest city of West Sumatra. It struck about 10 kilometers (6.2 miles) deep, making it a shallow earthquake, according to the country’s seismological agency.

The Indonesian agency immediately issued a tsunami warning for nearby coastlines, prompting residents in the region to flee coastlines in fear of a tsunami. The Pacific Tsunami Warning Center also issued a tsunami watch, but both alerts were canceled about an hour later.

While no destructive widespread tsunami was generated, the Pacific Tsunami Warning Center said it recorded several small tsunamis. While relatively small, the tsunami was large enough to travel hundreds of kilometers (miles) from the earthquake epicenter.

“A significant tsunami was generated by this earthquake,” the Honolulu-based agency said. “However, sea level readings now indicate that the threat has diminished or is over for most areas. Therefore the tsunami watch issued by this center is now cancelled.”

A tsunami expert at the agency told BNO News that the largest tsunami waves recorded were about half a meter (1.7 feet), which is measured relative to normal sea level and is not crest-to-trough wave height. He said he had no local information, but said a tsunami of that size has the potential to cause damage depending on local conditions.

According to the center, small tsunamis were recorded in Tanahbalah, Padang and Enggano in Indonesia. Additionally, a small 11 centimeters (0.4 feet) tsunami was recorded on the Cocos Islands of Australia, indicating the tsunami traveled hundreds of kilometers (miles).

There were no immediate reports of damage or casualties as a result of both the tsunamis as well as the earthquake, which the United States Geological Survey (USGS) measured at 7.5 on the Richter scale, considerably stronger than Indonesia’s estimate.

But both the USGS and the United Nations Office for the Coordination of Humanitarian Affairs said no severe damage or casualties were expected from the earthquake. “There is a low likelihood of casualties and damage,” the USGS said.

The agency estimated that approximately 11,000 people may have perceived very strong shaking, which could result in moderate to heavy damage. Another 6.5 million people may have felt weak to strong shaking, which would be unlikely to result in damage.

Soon after the initial earthquake, several aftershocks rattled the area. The first and largest aftershock, at 10.21 p.m. local time (1521 GMT), had a magnitude of 5.5 on the Richter scale. Two other aftershocks that followed in the hours after the first quake, had preliminary magnitudes of 5.0.

Indonesia is on the so-called ‘Pacific Ring of Fire’, an arc of fault lines circling the Pacific Basin that is prone to frequent and large earthquakes. Volcanic eruptions also occur frequently in the region.

On December 26, 2004, one of the most powerful earthquakes ever recorded struck off the west coast of Sumatra, Indonesia. The 9.1-magnitude earthquake unleashed a deadly tsunami, striking scores of countries. In all, at least 227,898 people were killed.

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