East Coast

After an earthquake hit Virginia in 2011 and was felt in Washington, D.C., Maryland, Delaware, New York and Pennsylvania, throughout New England and as far south as Georgia, the USGS found that earthquakes on the East Coast could travel further and cause more damage than originally thought. USGS says earthquake estimates for Charleston, S.C., have risen due to an assessment of earthquakes in the state.

The maps for New York City indicated that there may be a slightly lower hazard for buildings than previously thought, depending on the type of shaking that occurs. Taller structures are more likely to be impacted by slower shaking, while shorter buildings will suffer more damage from fast shaking.

Central U.S.

There is a high risk area that includes portions of Illinois, Missouri, Arkansas, Tennessee and Kentucky. The affected areas expand to include Indiana, Mississippi, and Alabama with a more moderate risk hazard. New research from the Nuclear Regulatory Commission assisted in identifying the risk for the area known as the New Madrid Seismic Zone. Most of the high risk area is adjacent to the Mississippi River.

West Coast

The high risk area for the West Coast ranges from Washington to the southernmost tip of California, and includes portions of the east coast of California and western Nevada. The entire region from the west coast of California to portions of Montana, Wyoming, Colorado, New Mexico and Texas, falls into the moderate to high hazard area.

The new information reduced the earthquake hazard for Irvine, Santa Barbara and Oakland, while increasing it for some parts of the San Francisco Bay Area and Los Angeles. Data from recent earthquakes in Mexico, New Zealand and Alaska allowed scientists to see how fault lines can link together, which expands the number of areas that can be impacted by a single event.

This science was applied to California, resulting in the modeling of approximately 250,000 complex ruptures. With new research on the Cascadia Subduction Zone, a fault that runs from Northern Vancouver Island to Cape Mendocino, Calif., earthquake magnitude estimates were increased to 9.3.

The value of research

The maps were the USGS contribution to the National Earthquake Hazards Reduction Program, part of a congressionally-established partnership comprising the USGS, Federal Emergency Management Agency, the National Institute of Standards and Technology, and the National Science Foundation. The information compiled from these agencies will allow states to have more accurate information in order to plan for worse-case scenarios.

“USGS earthquake science is vital because you can't plan for earthquakes if you don't know what you are planning for,” said Mark Petersen, Chief of the USGS National Seismic Hazard Mapping Project. “Our nation's population and exposure to large earthquakes has grown tremendously in recent years…It is important to understand the threat you face from earthquakes at home and the hazards for the places you might visit. The USGS is dedicated to applying the best available science in developing reliable products useful for reducing the earthquake risk across the U.S.”