Earthquakes used to be almost unheard of on the vast stretches of prairie that unfold across Texas, Kansas and Oklahoma.
But in recent months, temblors have become commonplace in some areas, rattling nerves and raising suspicions that the shaking might be connected to the oil and gas drilling method known as hydraulic fracturing.
Although most of the quakes are too weak to seriously damage property or endanger lives, anxious residents have harangued governments in all three states, which are finally beginning to confront the issue.
Officials are now reviewing scientific data, calling meetings and considering new regulations.
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Matt Skinner is a spokesman for the Oklahoma Corporation Commission, which regulates oil and gas drilling. He says the new process is all about managing risks.