Fort Smith and Northwest Arkansas areas do not sit on or near regularly active fault lines, but residents in the regions should pay attention to a new hazard map issued by the United States Geological Survey.
The reason, notes Geologist Scott Ausbrooks of the Arkansas Geological Survey, is because if the big one hits in northeast Arkansas — along the New Madrid Fault Line in what the USGS classified as being in the nation's highest hazard — impacts will be felt across the state and region.
"The effects of a 7.0 magnitude or greater along the New Madrid, especially on the southern extension from Blytheville (in Mississippi County, Ark.) to Marked Tree, will have a profound impact not just locally but regionally," he said. "The other impacts will be felt nationally."
For one, Ausbrooks said, an earthquake of that magnitude would be felt in cities like Fayetteville, Fort Smith and Rogers. He said it could be enough to make items fall off shelves, though he said heavy structural damage as far away as the northwest region of Arkansas would be unlikely.
Even though severe structural damage would be unlikely, infrastructure problems are likely to present themselves.
"You guys probably wouldn't have any damage, but it could impact power and communication that far out, especially if the grid is impacted. And just imagine Interstate 40 becoming a parking lot getting goods to the east. It would have some major impacts. Again, not directly where you're at, but indirectly there would be impacts."
But while it may seem far-fetched to some that an earthquake would even strike in Arkansas, Ausbrooks points to history as a guide and specifically pointing to the earthquakes along the New Madrid in 1811 and 1812 that many seismologists estimate registered as high as 9.0 magnitude and caused church bells to ring in Boston and resulted in damage hundreds of miles from the epicenter of New Madrid, Mo.
And the new maps released by the USGS rank the highest risk not simply based on the likelihood of another earthquake, but when the earthquake is likely to strike.
"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 USGS said in a press release.
In the 243-page study released with the updated maps, the USGS noted that more than 100 years of global earthquake observations were included in the map update process, which includes Arkansas as one of the 16 states with the highest risk of a major earthquake during the next half-century.
But the risks are coming from more than just the New Madrid, the map shows, with Oklahoma's earthquake risk rising, as well. It is that risk that Ausbrooks said could pose a greater threat to the Fort Smith and Northwest Arkansas regions, as the quakes in Oklahoma in recent years have tended to be more shallow and therefore felt more broadly and in some cases, more violently.
And while the New Madrid shows the highest risk, recent memory will remind locals in western Arkansas that Oklahoma's earthquakes — which have led to a rarely issued earthquake warning being issued for the state — are a closer threat. Ausbrooks notes that a 2011 earthquake centered near Prague, Okla., registered a 5.6 magnitude. The quake destroyed several homes in the area and shook items off shelves as far away as Arkansas, he noted.
"In fact, that (5.6) magnitude in Prague actually knocked pictures and stuff off the walls in Fort Smith. There was an impact that far away," Ausbrooks said, before noting that should a 6.0 or higher strike in central Oklahoma, the border region would likely see more of those impacts on a wider scale.
The bottom line, he said, is to take the USGS hazard map seriously and be prepared for the impacts of an earthquake just as you would a tornado or a flood.
"Have a basic flashlight and a call list. Non-perishable goods, batteries, things like that. And just have a plan of action. If something happens, where do you go? What do you do? Basic stuff like that will go a long way in preparedness," Ausbrooks said.