Water storage estimated from the regional GPS network throughout central and northern California shown as average water-layer thickness on a 25 km grid. The summer months experience a loss of water in the Sierra Nevada and Central Valley that is replenished in the mountains during the wet winter months as reservoirs fill and snow accumulates. In the Central Valley, water storage has been continuously decreasing due to large scale agriculture. The seasonal change in mass deforms the crust and the associated stress changes modulate regional seismicity. This material relates to a paper that appeared in the 16 June 2017, issue of Science, published by AAAS. The paper, by C.W. Johnson at University of California, Berkeley in Berkeley, CA, and colleagues was titled, "Seasonal water storage, stress modulation, and California seismicity."
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