California may be on the cusp of an oil fracking boom along its 1,750-square-mile Monterrey Shale Formation, which is potentially the richest shale oil reserve in the United States. Earthquakes have disturbed the layers of shale rock that run under most of the western state, making fracking more challenging than in a region like North Dakota. But when the next cyclical El Niño brings the huge amounts of water necessary for fracking, California could experience an economic boom similar to North Dakota’s oil rush.