The Central and Eastern U.S. experienced more than 300 earthquakes of at least magnitude 3.0 between 2010 and 2012, five times the number recorded between 1967 and 2000, according to a report from the U.S. Geological Survey. The increase may be related to wastewater disposal from oil and gas production, the report said. "There is a hazard, and I think it's greater than people thought before. If small earthquakes start occurring near injection sites, that's something to pay attention to. With that in mind, one can ask how this can be managed," said William Ellsworth of the USGS.