The New Madrid earthquake of 1811 was one of the most powerful and destructive earthquakes in American history. It occurred in the central United States, along the Mississippi River, and caused widespread damage to buildings and infrastructure throughout the region. But what was the estimated intensity of this earthquake?
According to modern estimates, the New Madrid earthquake of 1811 had a moment magnitude (Mw) of between 7.5 and 7.9. This measurement is based on modern seismological data and takes into account the size and duration of the earthquake’s seismic waves.
However, it’s important to note that moment magnitude is a relatively new scale that wasn’t developed until the mid-20th century. At the time of the New Madrid earthquake, there was no standardized way to measure earthquake intensity or magnitude.
Instead, historians and scientists have had to rely on historical accounts and records to estimate the strength of the earthquake. Based on these sources, it’s believed that the New Madrid earthquake reached an estimated intensity of between VIII and IX on the Modified Mercalli Intensity Scale (MMI).
The MMI is a scale that measures an earthquake’s intensity based on its effects on people, buildings, and other structures. It ranges from I (not felt) to XII (total destruction). An intensity level of VIII corresponds to “severe damage” while IX corresponds to “violent damage.”
Accounts from eyewitnesses describe widespread destruction throughout much of Missouri, Arkansas, Tennessee, Kentucky, Illinois, Indiana, Mississippi, and Louisiana. Buildings collapsed or were severely damaged; fissures opened in the ground; trees were uprooted; lakes formed where none had existed before; and sand boils erupted from beneath the soil.
While there are some discrepancies in historical accounts regarding specific details about the New Madrid earthquake – such as its exact duration or number of aftershocks – there is little doubt that it was a catastrophic event for those who experienced it firsthand.
In conclusion, the estimated intensity of the New Madrid earthquake of 1811 was likely between VIII and IX on the Modified Mercalli Intensity Scale. While modern seismological data suggests a moment magnitude of between 7.9, it’s important to remember that this scale didn’t exist at the time of the earthquake and that historical records are the best source of information about its impact.