HUNTSVILLE, Ala.(WHNT) - When it comes to earthquakes, the "big one" could be coming soon, and we're not talking about California or some place overseas.
Many people don't realize north Alabama lies in the impact zone of the New Madrid fault line, a sleeping giant that is approximately 20 times larger than California's famed San Andreas fault. The biggest earthquake in U.S. history happened in the New Madrid seismic zone in 1812, and in just the last few weeks, activity along the fault line is starting to heat up. An earthquake centered in eastern Arkansas rattled residents in multiple states in late October, making the quake the largest in the NMSZ in several years.
A recent earthquake study conducted by FEMA rated 12 Alabama counties as code critical, with those in northwest Alabama at highest risk of a New Madrid event. Geologists and other earthquake experts assessed the potential impact on Alabama in a WHNT News 19 special report.
"I think most people are aware that earthquakes can occur here, but they just can't remember the last time one shook them," said Gary Patterson, a geologist with the Center for Earthquake Research and Information in Memphis. "You take the same magnitude earthquake, put one in California, one here. The one here is going to affect 10 to 20 times larger an area. That's incredible...We know that the earthquakes of 1811, 1812 were felt 1,000 to 1,200 miles away."
The 1812 quake was actually the third and final act in a trilogy of megaquakes. The final earthquake had its epicenter in New Madrid, Missouri, a tiny town along the Mississippi River that inspired the name for the notorious fault line. Accounts of the 1812 quake vary since there were no measuring instruments at the time, but most geologists say evidence shows it was at least a magnitude 8 earthquake, and possibly a 9 or higher. The shaking was so intense that church bells started ringing as far away as Boston and New York. Chimneys toppled from the Deep South to Canada, and President James Madison was awoken by the violent shaking as he slept in the White House. Eyewitnesses said it even caused the Mississippi River to flow backwards for a time.
"We know that in 1811, 1812, there was some damage in tall buildings and structures in Charleston, South Carolina, and that's certainly farther away [from the epicenter] than Alabama," said Patterson. "Earthquake energy spreads out very efficiently here."
Alabama and eight other states that are part of the New Madrid zone were sparsely populated in 1812, but today tens of millions of people live in the same area. Hundreds of local emergency management agencies participated in a FEMA-run New Madrid earthquake drill last year, including those from north Alabama.
"Being in Lauderdale County, it's sort of the point of impact for the state of Alabama," said Tim Greer, Deputy Director of the Lauderdale County Emergency Management Agency. "Depending on the size of the seismic event, our county itself could be a part of the devastation... That may create problems in some of the roads because they may collapse, or some of the bridges may collapse... If we were to lose one of the bridges or anything in this area, that would be a significant event, obviously."
FEMA's scenario projected that more than 900 people in Alabama would be injured in a magnitude 7.7 New Madrid earthquake, along with almost 30 killed. Total casualties in all states are estimated at 86,000, with 3,500 of those victims listed by FEMA as fatalities. But experts say FEMA's simulation is based on an earthquake far less powerful than the 1812 megaquake. Geologists say the odds of a modern-day megaquake hitting in the next 50 years currently stand at 10 percent, but the odds greatly increase for earthquakes of a magnitude 6 or 7.
"The worst case scenario for earthquake hazard here in the central United States is a sequence of earthquakes, not just one," said Patterson. "It's one thing to be prepared for a magnitude 7, but if you have three magnitude 7's within a three-month period, with 12 to 15 magnitude 6's on top of it, and thousands of magnitude 4's and 5's in between, that's a whole different story. We're talking cumulative damage from earthquake sequences."
Experts said states that escaped physical damage from a New Madrid quake would still likely be paralyzed for days due to the interruption of crucial supply and communication lines. Emergency responders suggest having a basic plan that family members, and neighbors, can agree on.
"That includes where families should meet, alternate locations, how they should communicate with each other in case of a catastrophic event," said Greer. "Have flashlights, first aid kits, tarps, additional clothing if you can... My inclination is yeah, within our lifetime there will be some type of seismic event."
In February, Alabama and the other states in the New Madrid seismic zone will participate in the "Great Shakeout", a coordinated earthquake drill that many schools and businesses have already signed up for. According to FEMA, the other states in the New Madrid seismic zone are Tennessee, Mississippi, Arkansas, Missouri, Kentucky, Indiana, Illinois and Oklahoma. St. Louis and Memphis are the biggest metropolitan areas in the NMSZ.
North Alabama is also impacted by the East Tennessee fault line. This past Saturday, a magnitude 4.3 earthquake in the East Tennessee zone was felt in a few spots across north Alabama, along with locations spanning from Cincinnati to Atlanta.
Here are some helpful websites where you can learn more about earthquakes and their relation to Alabama: