Mapping the wake of a pending quake

December 4, 2006

Research into ancient earthquakes by scientists at USC and Caltech shows that within the next few decades another tsunami from another giant earthquake is likely to flood densely populated sections of western coastal Sumatra, south of those that devastated by the tsunami of Dec. 26, 2004.

The four researchers have modeled the process by which past quakes have flooded cities on that coast, hoping that a more detailed understanding of the future waves will speed preparations that could save lives. Their work will appear in the Proceedings of the National Academy of Sciences (PNAS) on December 4.

"The message of the 2004 tsunami has not been lost, at least in academia," said study participant Costas Synolakis, the director of the USC Viterbi School of Engineering Tsunami Reseach Center. "We are trying to be proactive and help prevent a similar disaster."

Fellow participant Kerry Sieh of Caltech explained, "When we tell people living along this 700-km section of the Sumatran coast that they will likely experience a big tsunami within the next 30 years, they ask for details. How much time after the earthquake will they have before the tsunami strikes" How big will the waves be" How far inland should they be prepared to run" What areas are likely to suffer tsunami damage" We can't answer these important questions without doing the work that we did for this paper."

The same big fault, or megathrust, that caused the tsunami of 2004 extends much farther southeastward, beneath the Indian ocean, just off the southwest coast of Sumatra. Rupture of this section of the megathrust, under the Mentawai islands, produced two great quakes and tsunamis in 1797 and 1833. Such events appear to recur on average every 230 years.

Samples of coral from the islands show how much these previous quakes lifted the sea floor. The patterns of uplift gave the scientists the information they needed to do computer simulations of the historical tsunamis. Synolakis says that the impact of the computed tsunamis is consistent with historical accounts.

The researchers say that this consistency gives them more confidence when they use the same model to evaluate worst-case scenarios from plausible future quakes. USC's Jose Borrero, the senior author of the study, says the results "confirm a substantial exposure of coastal Sumatran communities to tsunami surges." In particular, the coastal city of Bengkalu, with a population of 350,000, showed flooding in its river floodplain that extended up to several kilometers inland.

In the model, offshore islands appear to somewhat shield the larger city of Padang, but even then, the 1797 tsunami was reported to have carried a 200-ton English vessel into the town approximately a kilometer upstream, with smaller vessels carried yet further.

"The population of Padang in 1797 and 1833 was a few thousand," Sieh says. "Now it is about 800,000, and most of it is within a few meters of sea level. We hope that these initial results will help focus educational efforts, emergency preparedness activities, and changes in the basic infrastructure of cities and towns along the Sumatran coast."

Source: University of Southern California

Explore further: Cascadia initiative to monitor Northwest Pacific seismic risks

Related Stories

Sumatra earthquake mysteries examined

May 11, 2012

( -- An earthquake in the Indian Ocean off the coast of Sumatra, Indonesia on 11th April was unusually powerful, at magnitude 8.6, for a “strike-slip” type of quake, and a new analysis of the earthquake ...

Recent Indonesia quake added pressure to key fault

April 19, 2012

(AP) -- Seismologists say last week's powerful earthquake off western Indonesia increased pressure on the source of the devastating 2004 tsunami: a fault that could unleash another monster wave sometime in the next few decades.

New system can warn of tsunamis within minutes

March 4, 2011

Seismologists have developed a new system that could be used to warn future populations of an impending tsunami only minutes after the initial earthquake. The system, known as RTerg, could help reduce the death toll by giving ...

What Happened in Haiti?

January 20, 2010

( -- As the world focuses on the heart-wrenching losses and unbelievable devastation of the recent earthquake in Haiti, researchers at Michigan Technological University, discuss what happened there and why.

Recommended for you

Asteroid impact, volcanism were one-two punch for dinosaurs

October 1, 2015

Berkeley geologists have uncovered compelling evidence that an asteroid impact on Earth 66 million years ago accelerated the eruptions of volcanoes in India for hundreds of thousands of years, and that together these planet-wide ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.