The widespread practice of extracting California groundwater to irrigate the state's agricultural belt could be stressing the San Andreas Fault, which means it could also increase the likelihood of earthquakes occurring in the region.
In a study published in the scientific journal Nature on Wednesday, scientists reported that groundwater depletion in California's Central Valley could mean "significant but unexplored potential impacts on crustal deformation and seismicity." The authors add that “these results suggest that human activity may give rise to a gradual increase in the rate of earthquake occurrence."
Researchers have long-known that pumping groundwater has lowered the valley floor, but this is the first time that the agricultural practice has been linked to earthquakes in the region. Any earthquakes that do result from pressure on the faultline are likely to be very small, according to lead author Colin Amos. "The magnitude of these stress changes is exceedingly small compared to the stresses relieved during a large earthquake," said Amos. But his co-author, geoscientist Roland Bürgmann, warned that "in some circumstances such small stress changes can be the straw that breaks the camel's back," Bürgmann said. "It could just give that extra push to get a fault to fail."