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When winds blow, does the earth quake?

When winds blow, does the earth quake?

Unusual air pressure patterns off the coast of California may trigger some of the numerous moderate-size earthquakes in this state, according to a controversial report by a meteorologist who has been studying West Coast weather for several decades. If true, this finding may help seismologists predict months in advance the likelihood of earthquakes during certain atmospheric conditions.

As evidence for the pressure-earthquake connection, Jerome Namias of the Scripps Institutions of Oceanography in La Jolla, Calif., has found that California earthquakes are often preceded months in advance by persistent patterns of air pressure several hundred miles off the coast. Although he first noted this association more than 30 years ago, Namias only now has reported on the subject, in the April GEOPHYSICAL RESEARCH LETTER. In the past, seismologists have rejected outright the idea of any relationship, says Namias, and this criticism had kept him from raising the idea. While most earthquake experts remain highly skeptical, some have recently become more receptive to the possibility that patterns of air pressure may have some effect, he says.

Namias' paper reports on two series of southern California quakes--in July 1986 and October 1987. For a month to six weeks before the seismic activity, large, recurring patterns of high pressure developed off the coast. These pressure systems were much stronger than normal, says Namias. "In my experience, and judging from the large values and gradients, it seems unlikely that this correspondence is due to chance," he says.

Seismologists have long contended that air pressure has no effect on faults. And although he has faith in the association, Namias lacks a theory to explain how pressure patterns might indirectly trigger the release of stress built up along faults. He speculates, however, that pressure systems may generate winds or changes in sea level that could indirectly set off quakes.
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Title Annotation:link between air pressure and earth quakes
Publication:Science News
Date:May 7, 1988
Words:309
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