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Earthquakes

Earthquake Education
The science of earthquake prediction

Predicting quakes is an uncertain science
Thursday, March 1, 2001
By Dave Hogan of The Oregonian, reprinted with permission

No one was predicting that an earthquake centered near Olympia would rock the Northwest this week, this year or even this decade. That's because no one knows how to predict earthquakes with any certainty.

Nevertheless, Wednesday's quake was not surprising to the scientists who study and monitor earthquakes. They quickly point to the 7.1 temblor that hit the Olympia area in 1949, killing eight people.

"We operate on the assumption that if you had a big earthquake before, you can have one again in the same place," said Evelyn Roeloffs, a geophysicist with the Cascades Volcano Observatory in Vancouver, Wash. The observatory is part of the U.S. Geological Survey.

Roeloffs, who has done research on predicting earthquakes, said scientists around the world are working to learn more about how to know when and where earthquakes will occur.

Researchers in Greece are looking at predicting earthquakes by monitoring electrical signals from the ground.

In Japan, researchers have an intensive monitoring system in place to try to predict when a quake will repeat the one that killed 143,000 people in the Tokyo-Yokohama area in 1923.

Their system includes continuous Global Positioning System stations, which measure earth displacement, and borehole strain meters that measure expansion and contraction of the ground.

So far, however, the Japan system has been relatively quiet. "They haven't really seen any big changes that indicate anything big is about to happen," Roeloffs said.


Stations across Northwest
In the Northwest, there also are numerous monitors in place.

The University of Washington, in cooperation with the U.S. Geological Survey, monitors seismic activity in Washington and Oregon through dozens of seismograph stations throughout the Northwest.

In addition, the National Earthquake Information Center in Denver uses seismic information from stations around the world.

In the United States, scientists are preparing to ask Congress for money to establish a seismic monitoring system called the Plate Boundary Observatory. The elaborate network would include more than 1,500 instruments, including about 445 existing ones, from Alaska to California.

In the meantime, the most extensive earthquake monitoring is being done in California. In Parkfield, Calif., an elaborate system of instruments monitor ground movement along the San Andreas Fault. In that area about halfway between San Francisco and Los Angeles, earthquakes measuring around 6.0 have occurred about every 20 years, the most recent one was in 1966.

Based on the historic record and other evidence, the U.S. Geological Survey had predicted that an earthquake would hit the Parkfield area by the end of 1993.

There have been several scares. After a series of smaller quakes in 1993, for instance, the U.S. Geological Survey and the California Office of Emergency Services alerted the Parkfield area that there was a 37 percent chance of a 6.0 quake striking within days.

The alert was later canceled, however, and a quake of that magnitude still has not hit that area.

For details about predicting earthquakes, see the U.S. Geological Survey Web site:
Earthquake Topics - Prediction.


Pacific Northwest Earthquake Information from the Pacific Northwest Seismograph Network (PNSN)


While no one can predict earthquakes, you can build a seismometer to track earthquake activity around the world. Click here for more information.



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