Report: Eastern U.S. at greater risk for earthquakes

While the West remains the USA's primary hot spot for earthquakes, hazards appear to be growing in parts of the eastern and central U.S., according to a report and map released Thursday by the U.S. Geological Survey.

"The eastern U.S. has the potential for larger and more damaging earthquakes than considered in previous maps and assessments," the report states.

The geological survey issues new seismic hazard maps like this every six years;.the most recent map came out in 2008.

Most of the changes from the 2008 version are slight. Mark Petersen, chief of the National Seismic Hazard Project with the U.S.G.S., said parts of Washington, Oregon, Utah, Oklahoma, Colorado, Wyoming and Tennessee have now moved into the top two hazard zones.

Scientists "learned a lot" from the 5.8 magnitude quake that rattled the Mid-Atlantic and Northeast in 2011, as it was felt by tens of thousands of people. "It was among the largest earthquakes to occur along the East Coast in the last century, and helped determine that even larger events are possible," the report states.

The quake, centered in rural Virginia, was felt over a broad area, said Petersen, a much broader area than a similar quake would have been felt in California. He said the 2011 quake also raised awareness that the East can have big earthquakes too.

Earthquake hazards were also raised around Charleston, S.C., because of recent quakes in that region.

Additionally, an increase in earthquakes in the central U.S. could to be related to wastewater disposal from oil and gas drilling, especially in states such as Oklahoma. The report notes that "the importance of this phenomenon has increased since the 2008 map update because, since that update, there has been a dramatic increase in the earthquake count within the central U.S."

However, Petersen adds that while earthquakes occur near some wastewater disposal wells, they don't occur near all of them. Petersen said the agency will continue to study the phenomenon.

The map shows areas at greatest risk for future earthquakes in the U.S. and factors in how often quakes are likely to occur and how hard the ground should shake as a result. They are used for risk assessments, building codes, and insurance purposes, Petersen said.

"While all states have some potential for earthquakes, 42 of the 50 states have a reasonable chance of experiencing damaging ground shaking from an earthquake in 50 years (the typical lifetime of a building)," the report says,.

Parts of 16 states have the highest risk for earthquakes: Alaska, Hawaii, California, Oregon, Washington, Nevada, Utah, Idaho, Montana, Wyoming, Missouri, Arkansas, Tennessee, Illinois, Kentucky and South Carolina.

Want to avoid earthquakes entirely? Head for states such as North Dakota, Minnesota, Wisconsin and Florida. Those four states are almost entirely in the "lowest hazard" category.