Where are damaging earthquakes more likely to happen? New maps explains

(NEXSTAR) — While areas like California and the West Coast may be top of mind when you think of where earthquakes occur in the U.S., a new report shows nearly 75% of the country could experience a damaging earthquake.

The U.S. Geological Survey released a new map Tuesday showing which parts of the country are most at-risk for damaging earthquakes. It’s part of the latest USGS National Seismic Hazard Model, and was created using seismic studies, historical geologic data, and the latest data-collection technologies, according to a press release.

“Earthquakes are difficult to forecast but we’ve made great strides with this new model,” said Mark Petersen, USGS geophysicist and lead author of the study, in the release. “The update includes more faults, better-characterized land surfaces, and computational advancements in modeling that provide the most detailed view ever of the earthquake risks we face.”

According to USGS, this is the first comprehensive assessment of the entire country. Since the last version for the contiguous U.S. was released in 2018, researchers have found greater risks of damaging quakes in California and Alaska, as well as parts of the northeast, like Philadelphia, Boston, New York, and Washington, D.C. Hawaii is also listed as having a higher chance at damaging shaking because of “recent volcanic eruptions and seismic unrest on the islands.”

The USGS released the map, seen below, which shows the chance of “damaging earthquake shaking” that’s considered a VI on the Modified Mercalli Intensity scale occurring across the U.S. within the next century. That scale is based on the intensity of the quake, or how you or a building would experience it, Alexandra Hatem, a research geologist at the USGS who worked on the U.S. National Seismic Hazard Model, explained to Nexstar. It’s not the same as magnitude, which describes the earthquake itself.

Shaking equivalent to Modified Mercalli Intensity VI is considered strong, and is described as “felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.”

Areas that are dark red, like portions of southern Alaska and western California, have more than a 95% chance of experiencing damaging earthquake shaking like that over the next 100 years. Those that are shaded yellow have between a 25% and 50% chance of the same intense shaking.

As you can see, much of the country is green or blue, the lowest levels on the map. That doesn’t mean these areas can’t experience an earthquake. A 2.5 magnitude earthquake was detected in the northern Wisconsin community of Crandon, an area well within a section of blue on the map above. Based on user reports, the quake’s intensity ranked between I and III on the Modified Mercalli scale. Residents felt the shaking, but no damage was reported.

Instead, the map is intended to warn about strong quakes.

“[Intensity] changes as you change your distance, or what your building is built on as you go a different amount of distance away from the epicenter,” Hatem explains. The intensity used in the study serves as a “threshold that most people will feel and experience and have some memory of,” she adds.

One such earthquake happened in Texas late last year. On November 8, a 5.2-magnitude quake occurred near Coalson Draw, Nexstar’s KMID reports. In nearby Odessa, one resident reported patient beds and medical equipment shaking at Medical Center Hospital. Others said the shaking caused them to wake up and sent items falling from desks.

The intensity of the quake was estimated at VII strength on the Modified Mercalli scale. Actual user reports collected by the USGS put the shaking closer to VI intensity.

The map also doesn’t serve as a forecast for where a strong-intensity earthquake will happen, but rather highlights the areas at a higher chance of experiencing them. Quakes can happen anywhere, Hatem notes, though they do, of course, happen more frequently in some places than others.