The New Madrid Fault is one of the most unusual geological features in the United States. Located in the central part of the country, this fault system has been responsible for some of the largest earthquakes ever recorded in North America.
But what makes it so unique? Let’s take a closer look.
What is a fault?
Before we dive into what makes the New Madrid Fault unusual, let’s first define what a fault is. A fault is simply a crack or fracture in the earth’s crust.
When two plates in the earth’s crust move against each other, they can create stress that builds up over time. When that stress becomes too great, it can cause the plates to suddenly shift, resulting in an earthquake.
The New Madrid Fault
The New Madrid Fault is actually a series of faults that run through five states: Arkansas, Illinois, Kentucky, Missouri, and Tennessee. It was named after the town of New Madrid, Missouri where a series of devastating earthquakes occurred in 1811 and 1812.
What makes this fault system so unusual is that it is not located near any tectonic plate boundaries. Most earthquakes occur at plate boundaries where two plates are moving against each other. The New Madrid Fault, on the other hand, lies within the North American Plate.
Deep Seated Origin
Another unusual feature of this fault system is its deep-seated origin. Most faults are located within the upper few miles of the earth’s crust. However, studies have shown that the New Madrid Fault extends down into the mantle – some 15 to 20 miles below the surface.
This deep-seated origin may be one reason why earthquakes on this fault system can be felt over such a wide area. When an earthquake occurs on a shallow fault, most of its energy dissipates within just a few miles of the epicenter. But because earthquakes on the New Madrid Fault originate so deep underground, their energy can travel much farther.
Frequency of Earthquakes
Since the earthquakes of 1811 and 1812, there have been several other major earthquakes along the New Madrid Fault. However, what makes this fault system particularly unusual is that it experiences a relatively high frequency of moderate-sized earthquakes – those with magnitudes between 4 and 5.
According to the United States Geological Survey (USGS), there have been over 4,000 small to moderate-sized earthquakes in the central United States since 1974. While most of these were not felt by humans, they are evidence that this fault system is still active and capable of producing larger earthquakes in the future.
Conclusion
In summary, what makes the New Madrid Fault so unusual is its location within a tectonic plate rather than at a plate boundary, its deep-seated origin, and its relatively high frequency of moderate-sized earthquakes. While scientists cannot predict when or if another major earthquake will occur along this fault system, it is important for those living in the region to be aware of its potential hazards and to take steps to prepare for them.