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Pinpointing the Hazards

Though scientists can’t predict when earthquakes will occur, they can determine where they are most likely to strike and where shaking will be most violent. With a magnitude of 6.8, the 2001 Nisqually earthquake was a major seismic event. Yet magnitude was not the only issue. Some buildings, including the Washington State Capitol Building, were closed for months. Others were untouched. Research can pinpoint factors that affect the amount of damage and danger. This knowledge can help us build safer communities.

Earthquakes are more dangerous

Closer to the focus Communities that are closer to the focus of an earthquake usually experience stronger shaking.

Nearer to the surface Earthquakes that occur near the surface cause more damage than those deep underground.

As the shaking goes on The longer the shaking continues, the more damage it causes. The 2001 Nisqually earthquake lasted about 40 seconds. The 1700 subduction zone earthquake may have lasted five minutes.

On loose ground Loose materials—landfills and loose sediments—shake more than solid bedrock. Geologists compare this to a bowl of jelly. If it’s jostled, the bowl itself will shake just a little. But the jelly keeps on jiggling; it actually amplifies the motion.

On wet soil If loose soil is saturated with water, it may flow like a liquid when shaken in an earthquake. This process is called liquefaction. The soil loses its strength and no longer supports structures built upon it.

On slopes During quakes, slopes may slide. Also, if trees have been cut down, slopes are more vulnerable to earthquake damage. Slopes composed of loose backfilled materials may be unstable during quakes.

Near structures If you’re in the middle of a wheat field, you’re not likely to be hurt by an earthquake. Most damage—and most injuries—involve human structures. Unreinforced brick walls and chimneys can’t handle the side-to-side shaking of a large earthquake. Falling bricks are a major cause of injuries. Older concrete structures also may be unstable. And even a small earthquake may bring household objects down around your ears. Damage to lifelines—roads or bridges—can have life-changing impacts on area residents. Whole communities may be cut off from fire engines, ambulances, and supplies.


Research for safety

Although we can’t prevent earthquakes, engineering researchers are pioneering safer construction techniques to protect us from earthquake damage. Homes now are bolted to their foundations, brick and concrete are specially reinforced, and roads, bridges, and buildings are built with earthquakes in mind.



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© 2002 Burke Museum of Natural History & Culture
University of Washington, Seattle, WA 98195-3010

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