About 2:30 a.m. December 16, 1811, an earthquake threw people in New Madrid, Missouri Territory, out of bed and crumbled brick houses and cabin chimneys, forced the Mississippi River to run backward and change course, disturbed sleep along most of the East Coast, and toppled dishes from shelves in the White House.

That marked the beginning of some of the most powerful, prolonged quakes the United States has experienced. These weren’t the first in the New Madrid Seismic Zone, which is centered near where Missouri, Arkansas, Tennessee, and Kentucky come together. Geologists and other scientists have found indications that powerful quakes—rating 7 or higher on the Richter scale—have occurred there periodically for roughly 4,500 years.

Scores of small quakes—many in the 1.5 to 2.5 range—still pester area residents each year.

Geologists expect more big ones to come, estimating a 10% chance that will be within the next 50 years. The area between St. Louis and Memphis is likely to be the hardest hit, but right now the spread and range of the next disastrous earthquakes can’t be predicted any more precisely than the time.

Scientific research on the past and the possible future of the seismic zone continues. The quakes are not just an academic interest. In 2011, an expert panel concluded the zone “is at significant risk for damaging earthquakes that must be accounted for in urban planning and development.”

 My characters in Thunder Beneath My Feet had little information on what was happening elsewhere or what to expect as dozens of big quakes and aftershocks and hundreds of tremors hit New Madrid on an unpredictable schedule for weeks on end. Many people there, and elsewhere, thought the world was ending. For hundreds, it did.

I relished researching the unique historical events and creating characters representing the thriving, diverse (Spanish, French, American, Indigenous) community in the frontier riverport. For months, they faced daily terrors, and so will a much larger population when the next big ones hit.

Each fall preparedness groups in the area hold Great Shakeout Earthquake Drills. They recommend these three steps if you feel a quake begin.

1. Drop onto your hands and knees so you won’t fall down and can crawl to any nearby shelter.
2. Cover your head and neck with one arm and hand to protect you as you crawl under a table, desk, or anything else that will protect you from falling objects. If you have no shelter nearby, crawl to an interior wall, preferably a corner.
3. Hold on to your shelter but be ready to move if it gives way.

Happy anniversary.

—Carolyn Mulford