FEMA’s Nightmare: A Big Midwest Shaker

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The “Big One” assumed for California or other Pacific Rim states and provinces will almost certainly arrive some day, but FEMA said Thursday that the most catastrophic quake in the United States probably is destined for mid-America.

The feds didn’t say “biggest,” as in magnitude, but catastrophic, as in social upheaval and economic disruption. Based on a study by the University of Illinois’ Mid-America Earthquake Center, FEMA suggests “the total economic impact of a series of (New Madrid Seismic Zone) earthquakes is likely to constitute the highest economic losses due to a natural disaster in the United States.” The gist of the report — an exercise in predicting results of 10 quake scenarios — is a call for earthquake preparedness and a baseline for emergency response and recovery planning.

Citing other studies, the FEMA report says the chance of a magnitude 6 or 7 quake in the next 50 years is 90 percent.

New Madrid is often cited as the poster temblor for the nation’s midsection. The 1811 quakes emanating from the bootheel of Missouri caused property damage as far as Maine and Washington, D.C., and even changed the course of the Mississippi River. Earlier this year, after a 5.2 magnitude quake in Illinois was felt in 16 states, Michael Wysession, a seismologist at Washington University in St. Louis, told Miller-McCune.com that perhaps the Wabash Valley Fault, and not the New Madrid Fault, might be the one to worry about.

He told our Matt Palmquist:

New Madrid hasn’t even had a magnitude 6 earthquake or above in the last century. It hasn’t had a magnitude 5 or above in the last 35 years. Wabash has had two magnitude 5′s in the last six years.

The other thing is we notice no strain accumulating around the New Madrid fault. There’s no reason to suggest it will have another good-sized earthquake. Meanwhile, the Wabash Valley fault hasn’t had a large earthquake in the past few centuries; it may be more likely to be due.

FEMA, to its credit, isn’t focused just on New Madrid. While eight scenarios do follow putative 7.7 magnitude quakes along sections of New Madrid affecting eight states (Alabama, Arkansas, Illinois, Indiana, Kentucky, Mississippi, Missouri and Tennessee), the 106-page report also posits a 7.1 quake in the Wabash zone of southern Illinois and southeast Indiana and even a 5.9 shaker in the East Tennessee Seismic Zone in eastern Tennessee and northeastern Alabama. (By comparison, the 1906 San Francisco quake is estimated to have been a 7.9, the 2004 Boxing Day quake that caused the Indian Ocean tsunami was a 9.3 and the 1964 Alaska quake a 9.4.)

Although it’s not a contest, the biggest loser in these scenarios is the Volunteer State:

The results indicate that the State of Tennessee incurs the highest level of damage and social impacts. Over 250,000 buildings are moderately or more severely damaged, over 260,000 people are displaced and well over 60,000 casualties (injuries and fatalities) are expected. Total direct economic losses surpass $56 billion.

The State of Missouri also incurs substantial damage and loss, though estimates are less than those in Tennessee. Well over 80,000 buildings are damaged leaving more than 120,000 people displaced and causing over 15,000 casualties. Total direct economic losses in Missouri reach nearly $40 billion. Kentucky and Illinois also incur significant losses with total direct economic losses reaching approximately $45 (billion) and $35 billion, respectively.

Don’t feel smug if you live outside the zone. The feds expect “considerable national repercussions, as transportation routes, natural gas and oil transmission pipelines are broken and services are interrupted.”

Professor Wysession himself doesn’t think the biggest quake danger comes from his neck of the woods. He’s most afraid of the Cascadia Subduction Zone, which runs from the San Andreas Fault in Northern California to northern Vancouver Island.

“It would take more than 30 quakes of the whole San Andreas rupturing to equal one big earthquake beneath Seattle and Portland. It’s been over 300 years since the last one. We’re starting to get into that realm where the likelihood is increasing of it happening again.”

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