Groundwater depletion from California’s thirsty agriculture industry could cause increased earthquake risks, a new study shows.
Published online Wednesday in the journal Nature, the study explores how the water draining leads to a sinking of the ground by a few millimeters yearly in the drought-plagued Central Valley, while the surrounding mountains experience uplift by about the same amount.
“When humans deplete groundwater,” explained Maggie Benoit, program director in the National Science Foundation’s Division of Earth Sciences, which funded the research, “the amount of mass or material in Earth’s crust is reduced. That disrupts Earth’s force balances, causing uplift of nearby mountains and reducing a force that helps keep the San Andreas fault from slipping.”
As Roland Bürgmann, a geoscientist at the University of California, Berkeley and study co-author, stated, the uplift and sinking create stress on the infamous fault line.
“The stress is very small, much less than you need to build up stress on a fault leading to an earthquake, but in some circumstances such small stress changes can be the straw that breaks the camel’s back,” Bürgmann explained. “It could just give that extra push to get a fault to fail.”
While other studies have linked this kind of small stress change to earthquakes, those changes “were thought to be driven by rainfall and other hydrologic causes,” said study co-author and Western Washington University Assistant Professor of Geology Colin Amos.
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