Warnings help amid Indonesia’s tsunami scare

Posted April 11, 2012, at 6:49 p.m.

NEW DELHI — Warning and monitoring systems put in place following the 2004 Asian tsunami appeared to work well Wednesday after an 8.6-magnitude earthquake struck roughly the same area off Indonesia, said officials, civic groups and citizens in affected areas.

The real test, however, will come with another major disaster. On Wednesday no more than slightly higher than normal waves were seen in a few coastal towns along the southwestern coast of Sumatra island, with no reports of deaths or major damage.

The rapid dissemination of warnings and evacuation of coastal areas throughout the Indian Ocean, including fairly isolated communities, were helped along by fresh memories of the quake-generated tsunami that battered the region eight years ago, killing 230,000 people.

Also heading off complacency was the footage aired after Japan’s massive March 2011 tidal wave and nuclear disaster, motivating people to take the risk seriously, even though ultimately the wave proved elusive.

“Things worked quite well,” said Dailin Wang, oceanographer with the Pacific Tsunami Warning Center in Ewa Beach, Hawaii. The 2004 disaster “was not too long ago. People took it seriously and moved away from the coast. The challenge is to keep the knowledge alive.”

Wednesday’s earthquake, followed later by an 8.2-magnitude aftershock, was also deeper in the ocean and roughly twice as far from the Indonesian island of Sumatra as the 2004 temblor.

More importantly, it was of the strike-slip motion type often seen along the San Andreas Fault, said Bruce W. Presgrove, a geophysicist with the U.S. Geological Survey in Denver. That means tectonic plates move horizontally, which tends to displace less water and therefore present less of a tsunami risk than quakes generating significant vertical movement.

“In general, for an earthquake of this size, it’s prudent to issue things like this warning, even if a tsunami didn’t occur,” he said. “Prudence saves lives.”

Another factor that has helped in warning more people relative to 2004 is the prevalence of cellphones.

“The mass media, mobile telephones and [short messaging] mainly contributed to getting the word out,” said Suresh Bartlett, the World Vision charity’s national director for Sri Lanka. “The news got to everybody. Of course the roads were a bit congested as people tried to get to higher ground.”

So long as transmission towers and telecommunication infrastructure remain in place during a disaster, mobile phones can be more effective than tsunami sirens, which end up being posted every few miles and sometimes out of earshot, Wang said.

Television footage immediately after Wednesday’s earthquake showed terrified Indonesians pouring into the street, making cellphone calls and hugging each other in fear, some going back into buildings to find lost colleagues.

According to the U.S. Geological Survey, the quake was centered 20 miles beneath the ocean floor around 308 miles from the provincial capital Aceh on the Indonesian island of Sumatra.

Indonesian officials said lessons learned from 2004 were applied.

“The early warning system in [the affected areas of] Aceh and Padang and the west coast of Sumatra is much better,” said Sutopo Nugroho, data information chief at the National Disaster Mitigation Agency. “People have fled to mosques and churches in the affected areas. We have established better communication networks and we know from speaking with them that a tsunami has not struck.”

But some parts of the Indonesian system may not have been fully tested in this relatively mild quake. By law, local governments take the lead in a disaster, with the central government and military stepping in only if asked. But critics say local agencies are poorly funded and trained.

Nearly three-quarters of those who died after the 9.1-magnitude 2004 earthquake were from the province of Aceh, which was also shaken the hardest in Wednesday’s scare. But this time, residents as far away as Thailand and southern India said they also felt the earthquake, which helped in getting people motivated since they were directly affected.

Special correspondent Kate Lamb in Jakarta, Indonesia, contributed to this report.

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(c)2012 the Los Angeles Times

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