A 1,000-year sediment record of tsunami recurrence in northern Sumatra [Nature]

[Giuseppe]

A 1,000-year sediment record of tsunami recurrence in northern Sumatra [Nature]

A 1,000-year sediment record of tsunami recurrence in northern Sumatra

Nature 455, 1232 (2008). doi:10.1038/nature07374

Authors: Katrin Monecke, Willi Finger, David Klarer, Widjo Kongko, Brian G. McAdoo, Andrew L. Moore & Sam U. Sudrajat
The Indian Ocean tsunami of 26 December 2004 reached maximum wave heights of 35 m in Aceh, the northernmost province of Sumatra.

Both the tsunami and the associated Sumatra?Andaman earthquake were unprecedented in Acehnese history.

Here we use sand sheets to extend tsunami history 1,000 years into Aceh?s past.

The 2004 tsunami deposited a sand sheet up to 1.8 km inland on a marshy beach ridge plain.

Sediment cores from these coastal marshes revealed two older extensive sand sheets with similar sediment characteristics.

These sheets, deposited soon after ad 1290?1400 and ad 780?990, probably resulted from earlier tsunamis.

An additional sand sheet of limited extent might correlate with a documented smaller tsunami of ad 1907.

These findings, a first step towards a palaeotsunami record for northern Sumatra, suggest that damage-causing tsunamis in Aceh recur infrequently enough for entire human lifetimes to typically elapse between them.

Such recurrence adds to the challenge of preparing communities along the northern Indian Ocean shorelines for future tsunamis.
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[Sally Furniss]

Re: A 1,000-year sediment record of tsunami recurrence in northern Sumatra [Nature]

Devastating 2004 Indian Ocean Tsunami Wasn't First, Studies Say

By Ryan Flinn


<!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:266.2 --> <!-- WARNING: #foreach: $wnstory.ATTS: null at /bb/data/web/templates/webmacro_en/washingtonstory.wm:280.19 --> Oct. 29 (Bloomberg) -- The 2004 Indian Ocean tsunami that killed more than 220,000 people was so devastating that scientists couldn't point to its historical match in magnitude. Until now.



Scientists studying sand and sediment layers in Sumatra found evidence that the region was probably struck by a similar tsunami 600 or more years ago, according to two letters, from scientists from six nations, to be published in tomorrow's edition of the journal Nature.



Waves from the 2004 tsunami reached heights of 115 feet (35 meters) in Aceh, the northernmost province of Sumatra, depositing a sand sheet more than a mile inland, one of the letters said.



``Sediment cores from these coastal marshes revealed two older extensive sand sheets with similar sediment characteristics,'' according to the letter. ``These sheets, deposited soon after A.D. 1290-1400 and A.D. 780-990, probably resulted from earlier tsunamis.''



The Indonesian archipelago lies in a region where tectonic plates are constantly shifting. The 2004 tsunami that swept across the Indian Ocean, devastating coastal communities in Indonesia, Sri Lanka, India, Thailand and other countries was caused by a 9.1 temblor. There have been hundreds of earthquakes in Indonesia since then.


``Still to be determined is whether centuries dependably separate such outsize tsunamis of Sumatra-Andaman source, and whether these recur often enough to dominate Thailand's probabilistic tsunami hazard,'' one of the letters concluded.

``It can be hoped that natural warnings from recent geological history will help avert surprises from these additional tsunami sources.''



To contact the reporter on this story: Ryan Flinn in San Francisco at rflinn@bloomberg.net .
Last Updated: October 29, 2008 14:14 EDT

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