If you're wondering why the ground is shaking and your stuff is falling off the shelves, ask the people chanting "drill baby drill." ThinkProgress:
A U.S. Geological Survey (USGS) team has found that a sharp jump in earthquakes in America’s heartland appears to be linked to oil and natural gas drilling operations.
As hydraulic fracturing has exploded onto the scene, it has increasingly been connected to earthquakes. Some quakes may be caused by the original fracking — that is, by injecting a fluid mixture into the earth to release natural gas (or oil). More appear to be caused by reinjecting the resulting brine deep underground.