Looking for Clues to Predict Future Tsunamis

ByABC News
February 8, 2005, 10:02 AM

Feb. 9, 2005 — -- Scientists think they may have found a precursor to the kind of earthquake that sent a devastating tsunami crashing into wide areas along the northern Indian Ocean, killing at least 200,000 people. If they are right, it may be possible to warn coastal residents a few years before such an earthquake strikes, thus allowing time for protective measures to be taken.

But if they are wrong, they will join a large collection of scientists who have tried and failed to figure out when an earthquake is about to hit.

The technique applies to subduction zones, like the Pacific Northwest and parts of Alaska, where the oceanic plate is being pushed under the continental plate. Those regions are capable of generating what scientists call "megathrust" earthquakes, frequently resulting in tsunamis.

The technique won't work in seismically active regions like Southern California, where subduction is not the reason faults move. But it may prove to be a lifesaver in many areas of the globe where subduction rules the day.

Nowhere is that need any greater than along the northwest coastline of North America, which many experts believe is past due for a catastrophic quake.

"We think we're on to something," says Jere Lipps, professor of integrative biology at the University of California, Berkeley.

But, he adds quickly, it needs to be confirmed by other researchers.

Lipps and a team of researchers have found evidence that in the years preceding a megathrust earthquake, the coastal area subsides, or sinks, just about a foot. It's subtle, but it shows up clearly in the life and death of tiny microorganisms that dwell right along the high tide line.

Their most compelling evidence was found in Alaska, where a 9.2 magnitude quake struck on Good Friday, 1964, devastating much of Anchorage and a number of other communities and sending a tsunami that killed dozens along the west coast.

The researchers found that between five and 15 years before that deadly quake struck, the coastline near Anchorage sank about a foot.