New Madrid fault, << MAD rihd, >> is a fracture in Earth’s crust. It is marked by an active earthquake zone in the central Mississippi River Valley of the United States. The fault takes its name from a series of powerful earthquakes that occurred near New Madrid, in what became Missouri, in 1811 and 1812. The area around New Madrid contains several other faults. Together, these faults are often called the New Madrid Seismic Zone.
Description.
Earth’s outer shell consists of a number of rigid plates. The plates are in slow, continuous motion with respect to one another. The plates do not always slide past each other easily. Strain can build up along a fault until the rocks snap into a new position. The snapping releases energy, which causes earthquakes. Seismology is the study of these seismic waves (shock waves) produced by earthquakes.
The New Madrid Seismic Zone is centered in the Boot Heel region of southeastern Missouri. The zone extends south into Tennessee. It also includes parts of northeastern Arkansas, southern Illinois, and western Kentucky. More earthquakes occur in this region than in any other area of the United States east of the Rocky Mountains.
History.
Scientists believe that earthquakes have occurred in the New Madrid area for thousands of years. The town of New Madrid was founded in the 1780’s. Residents of the town were among the first to record the quakes’ effects.
Early in the morning of Dec. 16, 1811, the ground in the New Madrid area began to shake violently. People awoke to the shaking in places as far away as New York City. Hours later, people felt aftershocks (smaller quakes that follow a main earthquake) throughout the eastern United States. Another quake struck the New Madrid area on Jan. 23, 1812. One of the strongest of the New Madrid earthquakes occurred on Feb. 7, 1812. The quake destroyed log buildings throughout the region and triggered many landslides. It also caused the land to rise or fall dramatically in some areas.
Scientists estimate that the quakes had a magnitude of up to 8 on the Richter scale. Magnitude is a measurement of earthquake strength based on ground motion. Despite the severity of the quakes, few people died because the region was sparsely populated.
