Recent California floods could trigger earthquakes, new report says

As if we don’t have enough trouble from flooding, extreme amounts of rain caused by back-to-back storms systems in the state could create enough pressure in the groundwater system to trigger earthquakes along California’s faults, a new report says.

California has received record amounts of rain this winter, causing everything from dam failures to widespread flooding and mudslides. With that in mind, an article in The Conversation this week argues that academic research has shown a link between heavy rainfall and increased seismic activity in the past, raising concerns about the state’s potential for earthquakes in the near future.

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“Water pressure in the fault zone is important in controlling when a geological fault slips. Fault zones invariably contain groundwater, and if the pressure of this water increases, the fault may become ‘unclamped.’ The two sides are then free to slip past each other, causing an earthquake,” the report says.

The Conversation, which reports academic studies and findings, cited a swarm of earthquakes that developed after “intense rainfall near Mt. Hochstaufen in Germany and the Muotatal and Riemenstalden regions of Switzerland in 2002. The authors of the report are Gillian Foulger, p rofessor of geophysics, Durham University; Jon Gluyas, professor in geoenergy, carbon capture and storage atDurham University; and Miles Wilson, a doctoral tudent in the Department of Earth Sciences at Durham University.

“Hydrological changes do not need to be sudden or large to change the water pressure in a fault zone. As aquifers are depleted for irrigation, the water table slowly drops, which may also trigger earthquakes,” it reports. “It is thus unsurprising that extreme rainfall events might also encourage earthquakes. A number of instances of this have been flagged by scientists.”

California’s wet winter has refilled reservoirs and wiped out a historic drought in around 80 percent of the state, but the region’s saturated soil and swelling aquifers are creating conditions similar to water-induced mining, also known as fracking, the study’s authors argue. Fracking has been shown to increase seismic activity.

“Earthquakes are triggered by a tiny additional increment of stress added to a fault already loaded almost to breaking point. Many natural processes can provide this tiny increment of stress, including the movement of plate tectonics, a melting icecap, and even human activities,” the study says.

“For example, injecting water into boreholes– either for waste disposal or to drive residual oil out of depleted reservoirs – is particularly likely to trigger earthquakes.”

The report adds, “Any study of the relationship between weather and earthquakes is likely to take time, and the results to be controversial. In the meantime, now is a good time to check that your gas heater is earthquake-secure and your emergency drinking water is fresh. After all, a ‘big one’ could come at any time.

Article provided by: Sacramento Business Journal
Image provided by: seismic.ca.gov
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