Another earthquake rattled southern Missouri early this morning, making it the 40th such earthquake to hit over the last 30 days in the eastern United States. In recent weeks, earthquakes have struck New York, New Hampshire, Maine, Maryland, Virginia, South Carolina, Tennessee, Arkansas, North Carolina, and Missouri. Most of these earthquakes have struck in an area known as the New Madrid Seismic Zone and today’s earthquake wasn’t far from the heart of that zone.
Today’s relatively weak earthquake struck at 2:16 am local time; the magnitude 2.2 event struck at a depth of 13.8 km just west-northwest of West Plains in the Ozark Plateau region of south-central Missouri. While USGS confirmed the seismic event, the quake didn’t get anyone to use the “Did you feel it?” reporting tool on their website to report feeling any shaking or damage.
While today’s earthquake was close to the New Madrid Seismic Zone, it wasn’t actually within it. While not as well known for earthquakes as California or Alaska, the New Madrid Seismic Zone (NMSZ), located in southeastern Missouri, northeastern Arkansas, western Tennessee, western Kentucky and southern Illinois, is the most active seismic area in the United States, east of the Rocky Mountains.
The New Madrid Seismic Zone extends 120 miles south from Charleston, Missouri, following Interstate 55 to near Marked Tree, Arkansas. The NMSZ consists of a series of large, ancient faults that are buried beneath thick, soft sediments. These faults cross five state lines, the Mississippi River in three places, and the Ohio River in two places.
According to the Missouri Department of Public Safety, the New Madrid Seismic Zone is active and averages about 200 measured events per year (magnitude 1.0 or greater). Tremors large enough to be felt (magnitude 2.5 – 3.0) occur annually. On average every 18 months, the fault releases a shock of magnitude 4.0 or greater, which is capable of local minor damage. A magnitude 5.0 or greater occurs about once per decade, can cause significant damage and be felt in several states.
On December 16, 1811, at roughly 2:15am, a powerful 8.1 quake rocked northeast Arkansas in what is now known as the NMSZ. The earthquake was felt over much of the eastern United States, shaking people out of bed in places like New York City, Washington, DC, and Charleston, SC. The ground shook for an unbelievably long 1-3 minutes in areas hit hard by the quake, such as Nashville, TN and Louisville, KY. Ground movements were so violent near the epicenter that liquefaction of the ground was observed, with dirt and water thrown into the air by tens of feet. President James Madison and his wife Dolly felt the quake in the White House while church bells rang in Boston due to the shaking there.
But the quakes didn’t end there. From December 16, 1811 through to March of 1812, there were over 2,000 earthquakes reported in the central Midwest with 6,000-10,000 earthquakes located in the “Bootheel” of Missouri where the New Madid Seismic Zone is centered.
The second principal shock, a magnitude 7.8, occurred in Missouri weeks later on January 23, 1812, and the third, a 8.8, struck on February 7, 1812, along the Reelfoot fault in Missouri and Tennessee.
The main earthquakes and the intense aftershocks created significant damage and some loss of life, although lack of scientific tools and news gathering of that era weren’t able to capture the full magnitude of what had actually happened. Beyond shaking, the quakes also were responsible for triggering unusual natural phenomena in the area: earthquake lights, seismically heated water, and earthquake smog.
Residents in the Mississippi Valley reported they saw lights flashing from the ground. Scientists believe this phenomena was “seismoluminescence”; this light is generated when quartz crystals in the ground are squeezed. The “earthquake lights” were triggered during the primary quakes and strong aftershocks.
Water thrown up into the air from the ground, or the nearby Mississippi River, was also unusually warm. Scientists speculate that intense shaking and the resulting friction led to the water to heat, similar to the way a microwave oven stimulates molecules to shake and generate heat. Other scientists believe as the quartz crystals were squeezed, the light they emit also helped warm the water.
During the strong quakes, the skies turned so dark that residents claimed lit lamps didn’t help illuminate the area; they also said the air smelled bad and was hard to breathe. Scientists speculate this “earthquake smog” was caused by dust particles rising up from the surface, combining with the eruption of warm water molecules into the cold winter air. The result was a steamy, dusty cloud that cloaked the areas dealing with the quake.
The February 1812 earthquake was so intense that boaters on the Mississippi River reported that the flow of the water there reversed for several hours.
Today’s earthquake in southern Missouri serves as a gentle reminder that areas far from the U.S. West Coast are subject to occasional seismic activity.