USGS Map Shows 75% Of U.S. At Risk

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N​early 75% of the country is at risk for a potentially damaging earthquake in the next 100 years, according to a recently updated map from the U.S. Geological Survey.

T​he map is the first to include all 50 states in a single USGS assessment, and it shows risk in some places that weren't highlighted before.

M​ark Petersen, a USGS geophysicist who led the mapping team, said assessments like this one are fine-tuned over time as the science behind them gets better.

“And in the case of these maps, we have increased the hazard in many areas because we have added new details on the soils and how they modify the ground shaking," Petersen told weather.com in an interview. "We've added details on how faults rupture and how complex they might be.”

T​he update was released last year.

W​hat The USGS Earthquake Map Tells Us

The color-coded map shows a range of earthquake probability across the U.S. Well known high-risk areas, such as California and Alaska, are coded in dark red, denoting the highest risk.

But that same risk level exists in a small section of the Central U.S. Other lesser-known areas with some risk include Charleston, South Carolina, where a major earthquake happened in 1886.

T​he USGS estimates that 37 states have already experienced earthquakes greater than magnitude 5, which is considered to be "damaging."

"That doesn't mean that they all have them at the same rate because in California, Alaska and the Pacific Northwest, especially coastal regions, (earthquakes) are much, much more common, much higher frequencies than they are in the Central and Eastern U.S," Petersen said.

"So I think that the message is still that there's an increased risk in many populated areas of the U.S., but there are some places that are considerably higher risk than other places. And probably all states have some chance of future earthquakes."

T​he map's release came almost exactly on the 30th anniversary of the deadly Northridge earthquake in Los Angeles, the most recent major quake to hit the U.S.

T​ools like the USGS map are used to help inform building codes and structural design, as well as emergency management.

Petersen pointed out that small earthquakes happen frequently and often aren't felt at all. But large ones are an entirely different scenario.

"When they happen, they cause huge consequences and we need to design buildings so that they will be strong enough to withstand that shaking and not collapse on people and kill them," he said.

Here's How To Stay Safe

P​etersen recommends going to the Federal Emergency Management Agency website for earthquake preparedness and reading the tips on how to be ready for an earthquake.

T​hat includes practicing "drop, cover and hold on."

“I think the most important takeaway here is that everyone should know what to do in an earthquake, regardless of where you live," weather.com meteorologist Ari Sarsalari said. "It’s the same as being prepared for a tornado or hurricane or any other emergency.”

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