California Central Valley groundwater depletion slowly raises Sierra Nevada mountains

Winter rains and summer groundwater pumping in California’s Central Valley make the Sierra Nevada and Coast Mountain Ranges sink and rise by a few millimeters each year, creating stress on the state’s faults that could increase the risk of an earthquake. Gradual depletion of the Central Valley aquifer, because of groundwater pumping, also raises these mountain ranges by a similar amount each year–about the thickness of a dime–with a cumulative rise over the past 150 years of up to 15 centimeters (6 inches), according to calculations by a team of geophysicists. The scientists report their results in this week’s issue of the journal Nature.  While the seasonal changes in the Central Valley aquifer have not yet been firmly associated with any earthquakes, studies have shown that similar levels of periodic stress, such as that caused by the motions of the Moon and Sun, increase the number of microquakes on the...

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