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Way back in 1811 and 1812, a series of over 1,000 earthquakes rocked the Mississippi River between St. Louis and Memphis. One was so powerful that it caused the river to run backwards for a few hours.
Today, scientists say that the 150-mile-long New Madrid Seismic Zone has a terrifying 40% chance to blast in the next few decades, impacting 7 states – Illinois, Indiana, Missouri, Arkansas, Kentucky, Tennessee and Mississippi – with 715,000 buildings damaged and 2.6 millions of people left without power.
We all know the awesome power of the San Andreas fault. But there’s a fault in the Midwest that packs an even greater punch.
The New Madrid Seismic Zone, sometimes called the New Madrid Fault Line, is a major active seismic zone in the southern and midwestern United States. As shown in the map above, it stretches to the southwest from New Madrid, Missouri. Earthquakes that occur in the New Madrid Seismic Zone potentially threaten parts of 8 US states: Illinois, Indiana, Missouri, Akansas, Kentucky, Tennessee, Oklahoma, Mississippi.
The New Madrid fault system was responsible for the 1811–12 New Madrid earthquakes, an intense intraplate earthquake series that began with an initial earthquake of moment magnitude 7.5–7.9 on December 16, 1811, and was followed by a moment magnitude 7.4 aftershock on the same day. They remain the most powerful earthquakes to hit the contiguous United States east of the Rocky Mountains in recorded history.
The infamous New Madrid earthquakes of 1811-1812 rang church bells in Boston, which is 1,200 miles from St. Louis.
Unlike California, which has been super-prepared since the last major earthquake hit hard enough to delay the World Series, the New Madrid fault area has been sitting blissfully by.
In case the “40 percent” statistic didn’t bother you, this should: The New Madrid fault has an impact zone ten times as big as its more famous San Andreas cousin and most residents from all of the bordering states on the fault are totally unprepared, and the infrastructure is decades overdue for some quakeproofing.
As described by USGS: “In 1811, the extent of the area that experienced damaging earth motion, which produced Modified Mercalli Intensity greater than or equal to VII, is estimated to be 600,000 square kilometers. However, shaking strong enough to alarm the general population (intensity greater than or equal to V) occurred over an area of 2.5 million square kilometers.“
New Madrid vs. San Andreas
The unique geology in the Midwest increases the shaking intensity of earthquakes because energy from the New Madrid seismic zone moves through the dense bedrock underlying the mid-continent region at very high speeds, then becomes trapped in the soft sediments filling river channels and valleys.
Ground shaking would be magnified about 600 percent within the flood plain of the Missouri River, a development that would predict soil liquefaction and cause most of Missouri’s existing long-span bridges to collapse.
In contrast, the geology of California is thoroughly fractured by a series of faults, which, fortunately, serve to dampen seismic energy.
Now you know, a moderate to strong New Madrid earthquake in 2019 would be a national disaster. And it’s more than just knocking down buildings and structures in St. Louis. The real economic threat to the entire country is the disruption of communication and transportation lines, and underground pipelines, that move through the Midwest.
Lastly, you don’t get a warning from an earthquake. So my best advice if you live in this dangerous seismic active area of the United States is to have an earthquake plan – if you still don’t have one. And don’t wait too long, the next New Madrid Earthquake is slowly but surely building up!