SAN FRANCISCO (CBS SF) — California received a big dose of Nature’s wrath this week from a wild storm which brought widespread flooding and landslides to the Bay Area. Topping it off on Friday, the USGS reported at least 4 earthquakes in Northern California with magnitudes over 2.0. Could there be a connection? Maybe there is something to the idea of “earthquake weather,” after all.
The United States Geological Survey flatly debunks earthquake weather in a post on its website titled Earthquake Facts and Fantasy:
“Many people believe that earthquakes are more common in certain kinds of weather. In fact, no correlation with weather has been found. Earthquakes begin many kilometers (miles) below the region affected by surface weather. People tend to notice earthquakes that fit the pattern and forget the ones that don’t. Also, every region of the world has a story about earthquake weather, but the type of weather is whatever they had for their most memorable earthquake.”
Perhaps so, but with the Golden State experiencing its wettest weather in years, it’s surely not crazy to wonder whether all that water, percolating deep underground, might lubricate local seismic faults, producing more quake activity now or in the near future.
As for just how much water we got, KPIX meteorologist Paul Deanno received one estimate from a Silicon Valley engineer named Al Kovalick, who did some quick calculations and reckoned that 3.38 billion gallons of water fell on San Francisco on Thursday. That much water would weigh more than 28 billion pounds.
A CBS SF editor, inspired by that number, extended the napkin-calculations to the greater Bay Area. Using a conservative estimate of 3 inches of rainfall over 500 square miles, you get 217 billion pounds of water dropped suddenly over the very heart of Earthquake Country.
In a multi-year study of the Babaoshan fault in Beijing, China, researchers found that “rainfall plays a key role in fault deformation behavior through changing the pore pressure of fault zones… precipitation and groundwater may adjust the stress/strain field by controlling the deformation behavior of the fault.”
At the 2011 annual meeting of the American Geophysical Union in San Francisco, Shimon Wdowinski of the University of Miami, noted that a magnitude 6.4 quake which struck Taiwan in 2009 occurred only seven months after the area had been hit by Typhoon Morakot, which dropped 9.5 feet of rain in five days. “That’s about five times the average [annual] rainfall of San Francisco in five days,” Wdowinski said.
After plowing through 50 years of earthquake and weather records for Taiwan, Wdowinski found that large earthquakes above magnitude 6 were five times more likely to occur within four years after major rainfall events.
More recently, an article published in the scientific journal Nature reported that the pumping of groundwater for irrigation in California’s Central Valley is bending the surrounding mountains slightly upward, and could cause faults — including the San Andreas — to slip.
So take heart, pseudo-scientists and hunch-players. The USGS may sneer at the term “earthquake weather” but accepted wisdom is often shaken up by better data. And this rainy season is just getting started.
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