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.
Using new GPS data, the scientists found that mountains closest to California’s thirsty Central Valley were growing at a faster-than-expected rate compared to nearby ranges. The growth spurt — about 1 to 3 millimeters a year — was enough to lift them by half a foot over the last 150 years.
Groundwater is very heavy, and its weight depresses the Earth’s upper crust. Remove the weight, and the crust springs upward — and that change in pressure can trigger more small earthquakes, the researchers said.
“It reduces the forces that are keeping the fault clamped together — leading to more small earthquakes during dry periods of time,” said Colin B. Amos, assistant professor of geology at Western Washington University, the study’s lead author.
Other scientists studying a seismically active area of southern Monterey County near Parkfield observed that there tend to be more earthquakes during dry months than during wet months. The number of earthquakes there every year has roughly doubled between 1984 and 2005.
“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,” Amos said.
But the question as to why earthquakes have been increasing in Parkfield over time has been a mystery. The groundwater theory introduced by Amos and his colleagues gives one possible answer.
“Over the long term, because we’re losing more groundwater, it could give rise to more seismicity by reducing these overall forces,” Amos said.
Groundwater has been slowly depleted in the Central Valley to quench the thirst of farms and cities since the mid-1800s.
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As seen in: Property Casualty 360 4/25/2012 By Melissa Hillebrand
There is a federal insurance program in place that insurance agents use that specialize in Agriculture Insurance. Throughout the years this insurance program has gone through many different changes like cut backs like a lot of other programs are going though as well. The Federal Crop Insurance Program’s (FCIP) current bill with the Congress expired this September and that may mean even more cut backs for the program. Originally when the program was created during the depression era to help those farmers recover from the damages that occurred from the Dust Bowl.
The 2012 farm bill that is before congress would take the place of the current legislation that was passed back in 2008. The legislation that was passed in 2008 made it so that there was a reduction in the appropriation that is given to insurers that sale and serve crop insurance policies and the administrative fees for coverage with the policies are increased for farmers. The National Association of Farm Service Agency (FSA) County Office Employees (NASCOE) wants Congress to replace the private insurance agents with federal government employees (FSA), although there is much debate over where or not federal employees or private insurance agents should be the ones that handle the policies.
Although there is a significant amount of fear surrounding the Obama administration proposed plan to decrease the amount of subsidies to the industry by $8 billion over the course of 10 years, a reduction of ROI for crop insurers to 12% and having a reduction in producer-premium subsidies and how these changes will in turn affect farmers.
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McVey Insurance Agency did not create this content.