Earthquake of December 16, 1811 The main shock that occurred at 2:15 am on December 16, 1811, was a result of slippage along the Cottonwood Grove Fault in northeastern Arkansas. It was followed by at least three large aftershocks with magnitudes that ranged from 6.0 to 7.0 over the course of the next 48 hours. Despite the strength of the tremors, only minor damage to human-made structures was reported: from collapsing chimneys, falling trees, and cracking timbers in houses. Some areas sank, while others were uplifted. Fissures opened in the ground; some were filled with water from the nearby Mississippi River or wetlands, which was later expelled high into the air when the fissures closed. Soil liquefaction caused large sand blows that fouled farmland in Missouri, Tennessee, and Arkansas. On the Mississippi River itself, the shaking calved the soil along riverbanks and caused trees lining the river to fall into the water. Large waves formed on the water that capsized numerous boats and thrust others onto the land. Since the rocks in the eastern United States have few active faults to interrupt the propagation of seismic waves, ground vibrations from earthquakes generated in the region may travel thousands of miles. Shortly after the earthquake began, ground shaking was felt as far away as Canada in the north and the Gulf Coast in the south. Eyewitness accounts noted that the shaking rang church bells as far away as Boston, Massachusetts, and brought down chimneys in Cincinnati, Ohio, about 360 miles (580 km) away. U.S. Pres. James Madison is said to have felt the seismic waves arriving in Washington, D.C. In 2011 the results of a report prepared by the USGS noted that residents within an area of approximately 232,000 square miles (about 600,000 square km) experienced very strong ground shaking, and people living in an area of roughly 965,000 square miles (about 2,500,000 square km) experienced shaking that was intense enough to frighten them. Get exclusive access to content from our 1768 First Edition with your subscription. Subscribe today The strongest aftershock, a magnitude-7.0 tremor that became known as the “dawn aftershock,” occurred later that day at 7:15 am. The epicentre of the aftershock is a matter of some debate; some Earth scientists noted that it was located in northeastern Arkansas, whereas others maintained that it was located in northwestern Tennessee near the southern end of the Reelfoot Fault, a large fault running northwest-southeast within the Reelfoot Rift. Eyewitnesses reported that shaking from this temblor was severe, especially in New Bourbon, Missouri, but not as strong as the main shock. Like the main shock, however, seismic waves from this event were also felt in cities along the Eastern Seaboard.

Earthquake of January 23, 1812 The January 23 event was the smallest of the three principal earthquakes. The main shock occurred at 9:15 am, and its magnitude was estimated at 7.5. The location of the earthquake’s epicentre is controversial, but it is thought to have been located in the vicinity of New Madrid, Missouri, along a fault that runs perpendicular to the Reelfoot Fault. No appreciable damage to residences was reported; however, landscape changes, similar to those that occurred during the December 16 event, are thought to have taken place.