Researchers study effects of rainfall on earthquakes in CA

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With the recent unusually heavy rain, California might become a dynamic laboratory for Durham University researchers Gillian Foulger, Jon Gluyas and Miles Wilson, who are studying the potential associations between earthquakes and weather.

The researchers have been looking at the possibility that heavy rainfall may increase the chances of an earthquake. The group conducted a global review of human-induced earthquakes that occur in areas where there are industrial activities such as mining and water reservoir impoundment. During this examination of databases, they found examples of “flurries” of earthquakes after rainstorms, according to Foulger.

“We’re greatly expanding our understanding of what triggers earthquakes,” said Foulger, who is a professor of geophysics at Durham University. “It’s now more reasonable to look into this possibility that after a heavy rainfall water can seep into a fault zone and make it more possible for earthquakes to occur.”

Water from rainfall might make it easier for rocks in a fault zone to move, according to UC Berkeley professor of earth and planetary science Michael Manga. But Manga said that, if present, fluctuations in the number of earthquakes after rainfalls would be very small.

As the study notes, the proposed relationship would result predominantly in low-magnitude earthquakes, which may not be recorded in earthquake catalogs. The potential connection between rainfall and earthquakes is likely to require extensive computer modeling and statistical analysis to monitor, according to the study.

Geophysicist Art McGarr with the U.S. Geological Survey has reservations about the relationship between weather and earthquakes.

“I’ve gone back over our own earthquake catalog, through quite a few cycles of drought and heavy rainfall, and I didn’t see any unusual seismicity at all going back 40 or 50 years,” McGarr said. “The catalog has a magnitude threshold … so it could be that if you were able to record incredibly tiny earthquakes you could find a correlation.”

Apart from studying the relationship between weather and earthquakes, the researchers have also compiled an extensive online database, the Human-Induced Earthquake Database. Manga said the database is useful documentation. It includes a detailed map of human-induced earthquakes across the globe and describes the magnitude and the likely cause behind each earthquake.

James Rector, a professor in the campus department of civil and environmental engineering, said in an email that there are “trillions of very small quakes” caused by a variety of factors. Rector said in the email that if the question is what can cause a damaging earthquake, however, the probability of it being rainfall is unlikely.

“We’re not predicting a catastrophe,” Foulger said. “This is a very subtle effect … and scientists are interested in studying it to better understand the triggers behind earthquakes.”

Contact Shayann Hendricks at [email protected] and follow her on Twitter at @shayannih.

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