New Madrid Earthquakes of 1811–1812: When the Heartland Shook

Key Takeaways

• The New Madrid sequence consisted of three major earthquakes between December 1811 and February 1812, with estimated magnitudes ranging from ~M7.0 to ~M7.7 — among the largest earthquakes ever to strike the interior of North America.
• The earthquakes were felt across the entire eastern United States, from the Rocky Mountains to the Atlantic coast — an area of approximately 5 million km². Church bells reportedly rang in Boston, over 1,600 km from the epicenter, and damage occurred as far away as Cincinnati and Charleston, South Carolina.
• The earthquakes created Reelfoot Lake in northwestern Tennessee, caused the Mississippi River to temporarily flow backwards in some sections, produced massive sand blows still visible today, and dramatically altered the regional landscape.
• Because the region was sparsely populated in 1811–1812, casualties were relatively few (estimates range from dozens to several hundred). However, FEMA estimates that a repeat today would be among the most catastrophic natural disasters in U.S. history, affecting major cities including Memphis, St. Louis, Nashville, and Little Rock.
• The New Madrid Seismic Zone (NMSZ) demonstrates that devastating earthquakes can occur far from plate boundaries, in the interior of tectonic plates — a fact that remains poorly understood and underappreciated in public awareness.

Introduction

In the winter of 1811–1812, the Mississippi River valley experienced a series of earthquakes that remain unmatched in the recorded history of eastern North America. Over a span of roughly three months, at least three enormous earthquakes and hundreds of significant aftershocks shook the sparsely settled frontier along the central Mississippi.

The ground cracked open, ejecting sand and water in geysers that reached meters into the air. Entire islands in the Mississippi disappeared. The river itself was reported to have run backwards. A new lake — Reelfoot Lake, still one of Tennessee's most distinctive natural features — was created when the ground subsided and the Mississippi flooded the depression. The shaking was felt from the Rocky Mountains to the Atlantic seaboard, from Canada to the Gulf of Mexico.

These were not earthquakes along the San Andreas Fault or in the tectonically active Pacific Northwest. They occurred in the center of the North American plate, in what is now the boot heel of Missouri, the northwestern corner of Tennessee, and adjacent parts of Arkansas and Kentucky. The New Madrid Seismic Zone sits hundreds of kilometers from the nearest active plate boundary, and the reasons it produces large earthquakes remain one of the enduring puzzles of continental seismology.

The 1811–1812 earthquakes matter today because approximately 11 million people now live in the Memphis–St. Louis corridor directly atop the seismic zone. The question is not whether the New Madrid zone will produce another large earthquake, but when — and whether the region is prepared.

The Earthquake Sequence

Event 1: December 16, 1811 — The First Great Shock

At approximately 2:15 AM local time on December 16, 1811, the first major earthquake struck near the town of New Madrid, Missouri (then part of the Louisiana Territory). The town, situated on the west bank of the Mississippi River in what is now the boot heel of Missouri, was a small but significant trading post with a population of approximately 1,000.

Modern estimates place the magnitude at approximately M7.2–7.5, with the epicenter likely near the northeastern end of the New Madrid Seismic Zone, possibly in what is now northeastern Arkansas. The earthquake was accompanied by a foreshock of approximately M7.2 that struck around 2:15 AM, followed by the mainshock at approximately 2:15 AM (historical accounts are imprecise), and a major aftershock of approximately M7.0 around 7:15 AM.

Contemporary accounts describe the ground rolling in visible waves, the air filling with a sulfurous smell (from liquefied sediments), and the Mississippi River heaving so violently that boats were capsized and riverbanks collapsed. Trees snapped, log cabins collapsed, and vast areas of bottomland forest were knocked flat.

John Bradbury, a Scottish naturalist traveling on the Mississippi by boat, wrote one of the most detailed eyewitness accounts. He described being awakened by violent shaking, seeing the river fill with debris from collapsing banks, and hearing a noise "like the loudest thunder" followed by a "complete saturation of the atmosphere with sulphurous vapour."

Event 2: January 23, 1812 — The Second Major Earthquake

A second major earthquake struck on January 23, 1812, with an estimated magnitude of ~M7.0–7.3. The epicenter is believed to have been located in the central portion of the seismic zone, near what is now the town of New Madrid, Missouri.

Between the first and second major events, the region experienced constant aftershock activity. Contemporary residents reported that the ground seldom stopped shaking for long, with some accounts describing shocks "every day and many times a day" throughout the intervening weeks.

The January 23 event caused additional damage to already-weakened structures and further destabilized river banks. By this point, many settlers had abandoned their homes and were living in temporary shelters on higher ground, uncertain when — or whether — the shaking would stop.

Event 3: February 7, 1812 — The Largest Earthquake

The third and largest earthquake in the sequence struck at approximately 3:45 AM on February 7, 1812. Modern estimates place the magnitude at approximately M7.4–7.7, making it the largest earthquake in the sequence and potentially the largest in the recorded history of eastern North America.

This earthquake is believed to have ruptured the Reelfoot Fault, a thrust fault that runs beneath the northwestern corner of Tennessee. The rupture caused significant uplift on the northwestern side and subsidence on the southeastern side, creating the depression that would become Reelfoot Lake when water from the Mississippi and its tributaries filled the basin.

The February 7 event destroyed the town of New Madrid almost entirely. The Mississippi River was dramatically affected: contemporary accounts describe the river appearing to flow backwards for several hours as the riverbed was deformed by faulting. In reality, the tectonic uplift of a section of the riverbed near the Reelfoot Fault created a temporary dam and rapids, causing water upstream to back up and appear to reverse course. Two temporary waterfalls formed on the river, and numerous river islands were submerged or destroyed.

Table 1: The Three Major New Madrid Earthquakes

Note on magnitudes: The magnitudes of the 1811–1812 earthquakes are estimated from historical accounts and geological evidence (sand blow distributions, felt reports, structural damage). They cannot be measured instrumentally. Estimates have been debated for decades, with some researchers proposing magnitudes as high as M8.0+ and others arguing for values closer to M7.0. The ranges above represent the current moderate consensus based on work by multiple research groups including the USGS.

Dramatic Effects

Sand Blows and Liquefaction

The most widespread and geologically distinctive effect of the New Madrid earthquakes was massive liquefaction — a phenomenon where water-saturated, unconsolidated sediment behaves like a liquid during intense shaking. The Mississippi alluvial plain is underlain by deep deposits of loose sand and silt, making it extremely vulnerable to liquefaction.

During the earthquakes, pressurized water and sand were ejected through cracks in the ground surface, creating features called "sand blows" — conical deposits of light-colored sand that spread across the darker alluvial soil. The sand blows from 1811–1812 ranged from small patches a few meters across to enormous features spanning hundreds of meters.

Remarkably, many of these sand blows are still visible today, more than 200 years later. They appear in aerial photographs and satellite imagery as lighter patches in agricultural fields across northeastern Arkansas, the Missouri boot heel, and western Tennessee. Geologists have used these features to map the extent and intensity of the earthquake sequence.

Reelfoot Lake

The creation of Reelfoot Lake is perhaps the most dramatic permanent landscape change caused by the 1811–1812 earthquakes. Located in Obion and Lake Counties in northwestern Tennessee, the lake was formed when faulting along the Reelfoot Fault caused the land surface to subside by several meters on the southeastern side of the fault.

The depression was subsequently flooded by the Mississippi River and its tributaries, creating a shallow lake approximately 28 km long and up to 9 km wide, covering roughly 60 km² (15,000 acres). The lake is shallow — average depth is approximately 1.6 meters — and is characterized by standing dead cypress trees that were drowned when the area was flooded.

Today, Reelfoot Lake is a National Natural Landmark and a popular destination for fishing, birdwatching, and tourism. It is one of the few natural lakes in Tennessee (most are reservoirs) and remains a visible testament to the 1811–1812 earthquakes.

The Mississippi Flowing Backwards

One of the most famous anecdotes about the New Madrid earthquakes is that the Mississippi River "flowed backwards." While this has sometimes been dismissed as exaggeration, there is a physical basis for the accounts.

The February 7, 1812 earthquake caused tectonic uplift across the Reelfoot Fault, which crosses the Mississippi River channel. This uplift created a temporary obstruction — essentially a low dam or rapids — that caused water upstream of the uplift to back up. For a period estimated at several hours, the river water north of the obstruction did reverse direction, flowing upstream as the backed-up water sought its level.

Additionally, the violent shaking caused massive riverbank collapses that temporarily blocked and disrupted the river's flow. Eyewitnesses on boats described being swept upstream by the retrograde current.

The Mississippi eventually cut through the obstruction and resumed its normal flow, but the episode illustrates the enormous forces involved when faulting disrupts a major river system.

Felt Area

The 1811–1812 earthquakes were felt across an extraordinarily large area — far larger than comparably sized earthquakes in the western United States. The difference is geological: eastern North America is composed of old, cold, rigid rock that transmits seismic waves very efficiently, with little attenuation over distance.

The December 16, 1811 earthquake was felt over an area of approximately 5 million km², from the Rocky Mountains to the Atlantic coast and from southern Canada to the Gulf coast. Church bells reportedly rang in Boston, approximately 1,600 km from the epicenter. Chimneys were damaged in Cincinnati, approximately 600 km away. President James Madison reportedly felt the shaking in Washington, D.C.

For comparison, a magnitude 7.5 earthquake in California would typically be felt over an area roughly 10–20 times smaller. This difference in felt area is one of the reasons the New Madrid zone poses such a disproportionate hazard: a major earthquake there would affect far more people over a much wider area than a comparable earthquake on the West Coast.

Casualties and Damage in 1811–1812

Precise casualty figures for the 1811–1812 earthquakes are impossible to determine. The region was part of the frontier, with sparse European settlement and minimal record-keeping. Native American communities in the area undoubtedly experienced the earthquakes but left no written records.

Estimates of deaths range from as few as several dozen to perhaps several hundred. The low figures reflect the very sparse population: the entire Missouri Territory had fewer than 20,000 European residents in 1810, and the immediate epicentral area had far fewer. Many of the structures were simple log cabins that, while damaged, were less lethal in collapse than masonry buildings.

Property damage was extensive relative to what existed. The town of New Madrid was largely destroyed. The settlement of Little Prairie (near modern-day Caruthersville, Missouri) was abandoned entirely after the December earthquake, with residents fleeing to higher ground. Navigation on the Mississippi — the primary transportation artery for the western frontier — was severely disrupted for months by changed river channels, submerged islands, and debris.

Table 2: Reported Effects at Distance from Epicenter

Why Do Large Earthquakes Happen Here?

The Puzzle of Intraplate Seismicity

The New Madrid earthquakes occur far from any active plate boundary. The nearest plate boundary — the Mid-Atlantic Ridge — is over 5,000 km to the east. The San Andreas Fault system, where the Pacific plate meets the North American plate, is over 2,500 km to the west. The Ring of Fire is an ocean away.

This presents a fundamental scientific puzzle. Plate tectonic theory explains earthquakes at plate boundaries beautifully: stress builds as plates converge, diverge, or slide past each other, and is released in earthquakes. But in the middle of a tectonic plate, where does the stress come from?

Several hypotheses have been proposed for the New Madrid Seismic Zone:

Ancient rift zone: The most widely accepted explanation involves the Reelfoot Rift, a failed continental rift that formed approximately 600–500 million years ago during the breakup of the supercontinent Rodinia. The rift represents a zone of weakness in the continental crust that is being reactivated by modern stress fields. The rift is buried beneath several kilometers of sediment but has been mapped using seismic reflection surveys and gravity measurements.

Regional stress concentrations: The broad-scale stress field in eastern North America — generated by mid-Atlantic ridge push, gravitational potential energy from topography, and other plate-scale forces — may be concentrated along pre-existing zones of weakness like the Reelfoot Rift.

Glacial rebound: Some researchers have proposed that ongoing adjustments in the Earth's crust following the retreat of the Laurentide Ice Sheet (which covered much of North America until approximately 10,000 years ago) may be contributing to stress changes in the New Madrid area. However, the NMSZ is at the margin of the glaciated region, and this hypothesis remains debated.

Recurrence: How Often Do Large Earthquakes Happen Here?

Paleoseismic studies — investigations of geological evidence for prehistoric earthquakes — have revealed that the New Madrid zone has produced large earthquake sequences at least twice before the 1811–1812 events, at approximately 900 CE and approximately 1450 CE.

These dates come from radiocarbon dating of sand blows, which provide a geological record of prehistoric liquefaction episodes. The pattern suggests a rough recurrence interval of approximately 400–500 years for major earthquake sequences.

However, this recurrence interval is debated. Some researchers argue that the recurrence is more irregular and that the seismicity may be migrating or declining over time. Others have proposed that the current level of small earthquake activity in the NMSZ (dozens of small events per year) may not indicate that another large earthquake is imminent — a view that remains controversial.

Table 3: Known Major Earthquake Sequences on the New Madrid Seismic Zone

Modern Implications: What If It Happened Today?

Population and Infrastructure

The central Mississippi valley has changed almost beyond recognition since 1811. The region now contains several major metropolitan areas:

• Memphis, Tennessee: Population approximately 1.3 million (metro area), located approximately 200 km from the main seismic zone. Memphis sits on deep alluvial and loess deposits that would amplify seismic waves significantly.
• St. Louis, Missouri: Population approximately 2.8 million (metro area), located approximately 250 km north of the seismic zone.
• Nashville, Tennessee: Population approximately 2 million (metro area), 350 km east.
• Little Rock, Arkansas: Population approximately 740,000 (metro area), 200 km west.

Beyond the major cities, the NMSZ states (Tennessee, Missouri, Arkansas, Kentucky, Mississippi, Illinois) collectively contain tens of millions of residents, extensive infrastructure, and critical transportation corridors.

FEMA Damage Estimates

FEMA has studied the potential impact of a repeat of the 1811–1812 earthquake sequence. Their estimates are sobering:

A magnitude 7.7 earthquake on the New Madrid Seismic Zone could cause:

• Approximately 86,000 casualties (including an estimated 3,500 fatalities)
• $300+ billion in direct economic losses
• Destruction or severe damage to hundreds of thousands of buildings, most of which were not designed for significant seismic loads
• Disruption of major transportation including Interstate highways, Mississippi River navigation, railroad lines, and pipelines
• Potential damage to 15 major bridges crossing the Mississippi River in the affected area
• Disruption of critical infrastructure including water systems, natural gas pipelines, and electrical grids

The key factor driving these extreme estimates is the combination of a large earthquake with infrastructure that is largely not designed for seismic loads. Unlike California, where seismic building codes have been in place for decades, much of the construction in the central Mississippi valley has not been built to withstand significant earthquake shaking. Unreinforced masonry buildings — the most vulnerable structure type — remain common throughout the region.

Soil Amplification

The deep alluvial sediments of the Mississippi valley would dramatically amplify seismic waves. Memphis, in particular, sits on sediments up to 1,000 meters thick that would increase both the amplitude and duration of shaking relative to bedrock sites. Studies have shown that ground motion amplification in Memphis could be 2–5 times greater than what would be expected at a rock site the same distance from the fault.

This amplification effect is analogous to the damage patterns observed in the 1985 Mexico City earthquake, where soft lake sediments amplified seismic waves from a distant earthquake and caused devastating damage to the city.

Preparedness and Mitigation

Current Monitoring

The USGS and university partners operate a network of seismographs throughout the New Madrid Seismic Zone, recording dozens of small earthquakes each year. These small events (typically M1–3) confirm that the zone is seismically active but are too small to cause damage.

The Central United States Earthquake Consortium (CUSEC) coordinates preparedness planning among the eight states in the NMSZ region. Efforts include public education campaigns, building code adoption advocacy, and earthquake response planning.

Building Code Challenges

One of the most significant challenges for NMSZ preparedness is the slow adoption of modern seismic building codes. Unlike California, where seismic design requirements have been mandatory for decades, many jurisdictions in the central United States have been reluctant to adopt and enforce seismic provisions, citing the perceived low probability of a major earthquake and the added construction costs.

This situation creates a paradox: the earthquakes in the NMSZ are less frequent than in California, but the consequences of a major event would be disproportionately severe because the built environment is far more vulnerable.

ShakeOut Exercises

The Great Central U.S. ShakeOut, held annually, is a mass earthquake drill designed to raise awareness and promote preparedness. Millions of participants across the NMSZ states practice drop, cover, and hold on procedures. While a drill cannot substitute for proper building design, public awareness of the seismic risk is a critical first step.

Map Specification

Title: New Madrid Seismic Zone — 1811–1812 Epicenters, Felt Area, and Modern Cities

Map Coverage: Central and Eastern United States

Key Features to Display:

• Three estimated epicenter locations (Dec 16 1811, Jan 23 1812, Feb 7 1812)
• New Madrid Seismic Zone outline (approximately 240 km long, NE-SW trending)
• Reelfoot Fault trace
• Reelfoot Lake location
• Felt area boundary (approximate 5 million km²): entire eastern US, southern Canada
• Modified Mercalli Intensity contours (concentric, showing damage zone ~600 km radius)
• Modern cities overlay: Memphis, St. Louis, Nashville, Little Rock, Louisville, Cincinnati, Indianapolis, Chicago
• Mississippi River
• Inset: Close-up of NMSZ showing fault traces, sand blow distribution, Reelfoot Lake

Chart Specification

Chart 1: Felt Area Comparison — New Madrid vs. Western U.S. Earthquakes

• Type: Comparative bar chart or area diagram
• Data:
  • 1811 New Madrid (~M7.5): ~5,000,000 km² felt area
  • 1906 San Francisco (M7.9): ~800,000 km² felt area
  • 1994 Northridge (M6.7): ~80,000 km² felt area
  • 2011 Virginia (M5.8): ~4,000,000 km² felt area (eastern US rock, for comparison)
• Note: Eastern earthquakes are felt over much larger areas due to efficient wave propagation through older, colder, more rigid continental crust

Sources

1. Johnston, A.C., and Schweig, E.S. (1996). "The Enigma of the New Madrid Earthquakes of 1811–1812." Annual Review of Earth and Planetary Sciences, 24, 339–384.
2. Tuttle, M.P., et al. (2002). "The earthquake potential of the New Madrid Seismic Zone." Bulletin of the Seismological Society of America, 92(6), 2080–2089.
3. U.S. Geological Survey. "New Madrid Seismic Zone." USGS NMSZ
4. Hough, S.E. (2004). "Scientific overview and historical context of the 1811–1812 New Madrid earthquake sequence." Annals of Geophysics, 47(2/3).
5. FEMA (2008). HAZUS-MH Estimated Annualized Earthquake Losses for the United States. FEMA 366.
6. Fuller, M.L. (1912). "The New Madrid Earthquake." USGS Bulletin 494. USGS Bulletin 494
7. Central United States Earthquake Consortium (CUSEC). "New Madrid Seismic Zone." CUSEC
8. Penick, J.L., Jr. (1981). The New Madrid Earthquakes. University of Missouri Press.
9. Bradbury, John (1817). Travels in the Interior of America. Liverpool: Smith and Galway.