WUSTL seismologist: Tsunami warning system needed in Indian Ocean

Tens of thousands of people who perished in the Indonesia tsunami would be alive today had there been a warning system in place in the Indian Ocean basin similar to one in place for 40 years in the Pacific Ocean, says a seismologist at Washington University in St. Louis.

Douglas A. Wiens, Ph.D., Washington University professor of earth and planetary sciences in Art & Sciences, says it’s unfortunate, but the catastrophic tragedy will be the catalyst for developing such a system, just as the 1964 Alaska tsunami event triggered the installment of the current Pacific Ocean system.” It would have been an easy matter to warn people had there been a system set up because it took two hours for the waves to hit India and Sri Lanka,” Wiens said. “I think now there will be a significant warning system as a result of this tragedy, even though it might not be needed for another 50 years.”

Calm seas can turn deadly...
Calm seas can turn deadly…

Wiens specializes in large, deep earthquakes and has studied earthquakes and tsunamis all around the world. He said there is no comfort in thinking a “Paul Revere” kind of seismologist could have made a difference in saving lives.

“The system really has to be set up ahead of time,” he said. “In the recent Indonesia case, scientists throughout the world could see from the seismic records that there was going to be a terrible tragedy. However, there was no system in place to warn the governments and people in the Indian Ocean region. ”

One of the major reasons there had been no system in the Indian Ocean is that the region hadn’t experienced a disastrous tsunami for more than 100 years, Wiens said. On the other hand, major tsunamis have hit Pacific Coast nations in 1946, ’57, ’60 and ’64. The 1960 Chile event, at magnitude 9.5, and the 1964 Alaska quake at 9.2, are the largest earthquakes ever recorded and prompted the establishment of the Pacific tsunami warning system.

...when a tsunami strikes.
…when a tsunami strikes.

The Pacific network is comprised of seismograph stations, underwater pressure gauges, ocean buoys and a communication warning system among the countries and islands. The initial analysis is based on seismograph recordings, and triggers an alert when a large earthquake is detected. Then scientists can monitor underwater pressure gauges and buoys in various parts of the Pacific that actually record the tsunami as it goes over the gauges.

“I think the pressure gauges and buoys will be part of a system for the Indian Ocean countries, and there is some debate over whether they are needed in the Atlantic because historically there have been few tsunamis there,” Wiens said.

Wiens said that seismometers can tell seismologists the location and size of an earthquake within minutes. Predicting the likelihood of a killer tsunami gets more complicated after that assessment. One thing seismologists have to interpret from the data is the motion of the fault. If it is a side-to-side slippage (such as the motion in the San Andreas fault), it won’t generate as big of a wave as a motion that occurs when something is pushed upward. Think of your bathtub and imagine the floor of it being pushed up. Wiens said that was the case with the Indonesia earthquake – the sea floor was pushed up, which generated such a large wave traveling through the ocean at 500 miles per hour.

A second thing that needs to be determined is how shallow the earthquake is; shallower earthquakes generate waves that are larger than deeper earthquakes. Finally, seismologists know that the strongest waves travel in a direction that is perpendicular to the fault.

“The direction of the damaging tsunami waves was predictable because it was known exactly where the earthquake occurred and what kind of fault moved,” he said.

Since 1965, about 75% of the tsunami warnings in the Pacific have been false alarms, when no large tsunami was produced. The false alarm rate should become much lower after the recent addition of the pressure gauge and buoy sensors.

While the Pacific Ocean data network sometimes is inaccurate (think of Homeland Security or tornado warnings), Wiens said it’s not a good idea for people to become blasé about warnings. He notes that, despite warnings of the imminent tsunami danger from the 1964 Anchorage, Alaska, earthquake, eleven people,, some of whom came out to the coast to watch, were killed in Crescent, Calif. by the tsunami.

“It’s good that the Pacific system is in place, but it was done only following a disaster,” he said. “One of these years there is bound to be another large Pacific tsunami, but the system is in place and there won’t be a large loss of life as happened with the Indonesian case.”