– For years, scientists have wondered about the forces that keep pushing up California’s mighty Sierra Nevada and Coast Ranges, causing an increase in the number of earthquakes in one part of Central California. On Wednesday, a group of scientists offered a new, intriguing theory: The quakes are triggered in part by the pumping of groundwater in the Central Valley, which produces crops that feed the nation. “These results suggest that human activity may give rise to a gradual increase in the rate of earthquake occurrence,” said the study published in the journal Nature. “During wet periods of time when the fault is loaded down, the forces that are keeping the fault clamped down are greater. It inhibits the sliding of the fault,” says Colin B. Amos, assistant professor of geology at Western Washington University. More