For those who are complacent about the likelihood of tsunamis hitting the coastal regions around the Bay of Bengal, yesterday was another wake-up call.
The tsunami, set off by a 7.7-magnitude undersea quake, slammed into the southern part of the remote Mentawai Islands, wreaking havoc in villages and, the authorities believe, sweeping scores out to sea. The islands are a popular destination for foreign surfers, particularly Australians. The surge reached as high as 10 feet and advanced as far as 2,000 feet inland, officials at the Health Ministry’s crisis center said.
The earthquake occurred along the same fault that produced a 9.1-magnitude quake on Dec. 26, 2004, spawning a tsunami that killed an estimated 230,000 people around the Indian Ocean. The hardest-hit area was in Aceh Province in northern Sumatra.
Monday’s quake was along a shorter section of the fault, about 500 miles southeast of the 2004 rupture, that last had a major quake in 1833, said Leonardo Seeber, a research scientist at Lamont-Doherty Earth Observatory of Columbia University in Palisades, N.Y.
David Walsh, an oceanographer at the Pacific Tsunami Warning Center in Hawaii, said that the center issued a “local tsunami watch” seven minutes after the earthquake occurred, but that a “destructive widespread threat” did not exist. The warning was canceled several hours later.
Dr Charitha Pattiaratchi of the U of Western Australia is the authority on the subject, receiving real-time results from two tidal gauges off the Sri Lanka coast. If I recall correctly, he has documented water-level rises off Sri Lanka every year since 2004, except one.
Yesterday’s tragedy that killed over 100 people off the Sumatra Coast also points to the potential significance of Dr Pattiaratchi’s line of research that seeks to identify the geographical marker on the crescent-shaped fault that is generating these earthquakes in terms of danger to his countries of origin and residence. If he succeeds, the authorities in Sri Lanka can rest easy when earthquakes occur south of that point, while those in Perth will have to stay alert.
It seems that the Sri Lankan authorities rested easy yesterday. This is an improvement from the unnecessary evacuations ordered by successive Presidents in the past.
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