Login Register Subscribe
Current Issue

New USGS maps expand earthquake risks to 42 states


New seismic hazard maps from the U.S. Geological Survey show 42 states facing a “reasonable” chance of experiencing damaging ground shaking from an earthquake in 50 years, with 16 of those states facing a high risk of damaging ground shaking.

The latter group has historically experienced earthquakes with a magnitude 6 or greater, the USGS said Thursday in a statement announcing the new maps.

The 16 states the USGS identified as being at highest risk are Alaska, Arkansas, California, Hawaii, Idaho, Illinois, Kentucky, Missouri, Montana, Nevada, Oregon, South Carolina, Tennessee, Utah, Washington and Wyoming.

The USGS said that while the broad conclusions of seismic risks on a national level are similar to those in the previous maps released in 2008, the details and estimates of risks for many cities and states differ in the new maps from those in their last edition. Increased data and updated earthquake models have shown several areas as having the potential for larger and more powerful earthquakes than previously thought, the USGS said.

Among the noteworthy updates in the new maps is that the Eastern U.S. is shown to have the potential for larger and more damaging earthquakes than reflected in previous maps and assessments, according to the USGS. Among other things, scientists learned from the magnitude-5.8 earthquake that hit Virginia in 2011 that even larger events are possible. Also, estimates of earthquake risks near Charleston, South Carolina, have increased, the USGS said.

In the Central U.S., the New Madrid Zone was shown to have a larger range of potential earthquake magnitudes than previously identified, according to the USGS.

On the West Coast, the new maps show earthquake hazards extending over a wider area of California than previously thought. Overall, new knowledge resulted in increased earthquake hazard risks being depicted in some areas of California in the new maps, while estimates were reduced in others.

In the Pacific Northwest, new research on the Cascadia Subduction Zone led to increases in estimates of earthquake magnitude up to 9.3, the USGS said, with earthquake shaking estimates also increased.

The new maps can be viewed online.