The USGS recently updated their U.S. National Seismic Hazard Maps, which reflect the best and most current understanding of where future earthquakes will occur, how often they will occur, and how hard the ground will likely shake as a result.
42 States at Risk; 16 States at High Risk
Students conduct the “drop, cover, hold on” safety procedure during an earthquake preparedness drill. Photo Credit: Jessica Robertson, USGS
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). Scientists also conclude that 16 states have a relatively high likelihood of experiencing damaging ground shaking. These states have historically experienced earthquakes with a magnitude 6 or greater.
The hazard is especially high along the west coast, intermountain west, and in several active regions of the central and eastern U.S., such as near New Madrid, MO, and near Charleston, SC. The 16 states at highest risk are Alaska, Arkansas, California, Hawaii, Idaho, Illinois, Kentucky, Missouri, Montana, Nevada, Oregon, South Carolina, Tennessee, Utah, Washington, and Wyoming. [Since the last map, 2008] Several areas have been identified as being capable of having the potential for larger and more powerful earthquakes than previously thought due to more data and updated earthquake models. The most prominent changes are discussed below.
Changes: East Coast
The eastern U.S. has the potential for larger and more damaging earthquakes than considered in previous maps and assessments. As one example, scientists learned a lot following the magnitude 5.8 earthquake that struck Virginia in 2011. 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. Estimates of earthquake hazards near Charleston, SC, have also gone up due to the assessment of earthquakes in the state.
The New Madrid Seismic Zone has been identified to have a larger range of potential earthquake magnitudes and locations than previously identified. This is a result of a range of new research, part of which was recently compiled by the Nuclear Regulatory Commission.
In California, earthquake hazard extends over a wider area than previously thought. Most notably, faults were recently discovered, raising earthquake hazard estimates for San Jose, Vallejo and San Diego. On the other hand, new insights on faults and rupture processes reduced earthquake hazard estimates for Irvine, Santa Barbara and Oakland.
New research on the Cascadia Subduction Zone resulted in increased estimates of earthquake magnitude up to magnitude 9.3.
Earthquake hazard also increased for Las Vegas because of new science.
Full report here