The New Madrid earthquake, which occurred in 1811 and 1812, is considered to be one of the most powerful earthquakes ever experienced in North America. The quake was so strong that it caused the Mississippi River to flow backward for a short period and created several new lakes in the area.
But what kind of fault caused such a massive earthquake? Let’s find out.
The New Madrid Seismic Zone
The New Madrid Seismic Zone (NMSZ) is an area that spans across several states in the central United States, including Arkansas, Missouri, Tennessee, and Kentucky. It is named after the town of New Madrid, Missouri, where a series of powerful earthquakes occurred in 1811 and 1812. The NMSZ is still active today and continues to experience small earthquakes from time to time.
Intraplate Earthquakes
Unlike most earthquakes that occur near tectonic plate boundaries, the earthquakes in the NMSZ are considered intraplate earthquakes. Intraplate earthquakes occur within a tectonic plate rather than at its boundary. The cause of intraplate earthquakes is still somewhat unclear, but scientists believe that they may be due to stress buildup within the Earth’s crust.
Reactivated Faults
One theory about the cause of the New Madrid earthquake is that it was caused by reactivated faults. A fault is a fracture in the Earth’s crust where two blocks of rock have moved relative to each other. Faults can be active or inactive depending on whether they are currently moving or not.
Scientists believe that there are ancient faults within the NMSZ that were reactivated during the 1811-1812 earthquake sequence. These faults may have originally formed millions of years ago during earlier tectonic activity.
Slab Pull
Another theory about why intraplate earthquakes occur is known as slab pull. Slab pull is the force that is created when a dense oceanic plate subducts, or moves beneath, a less dense continental plate. The force of the subducting plate pulling on the overlying plate can cause stress buildup, which can result in intraplate earthquakes.
While there are no subduction zones in the central United States, some scientists believe that the North American Plate may be very slowly moving westward over the Pacific Plate. This movement may be creating stress within the NMSZ and causing intraplate earthquakes like those that occurred in 1811-1812.
Conclusion
In conclusion, while the exact cause of the New Madrid earthquake remains somewhat unclear, scientists believe that it was likely caused by reactivated faults within the NMSZ. The ongoing activity in the region suggests that there may be further earthquakes to come in the future. By studying past and present seismic activity in this area, we can better understand how intraplate earthquakes occur and prepare for potential future events.