Many people wonder about the potential for earthquakes in Tennessee and whether the state lies on a fault line. Understanding Tennessee’s seismic activity is a common concern, especially given historical events in the region. This article clarifies the geological realities and associated risks, providing insights into the state’s seismic landscape.
The Primary Seismic Zone Affecting Tennessee
Tennessee is significantly impacted by the New Madrid Seismic Zone (NMSZ), a major seismic zone stretching through the Southern and Midwestern United States. This zone extends southwest from New Madrid, Missouri, covering parts of seven states, including Illinois, Missouri, Arkansas, Kentucky, and West Tennessee. The NMSZ is approximately 150 miles (240 km) long and is a source of intraplate earthquakes.
Unlike earthquakes at plate boundaries, the NMSZ is an intraplate seismic zone, located within the North American plate’s interior. This zone poses a seismic threat to a wide area, with Tennessee’s western portion being particularly vulnerable. The faults responsible for the NMSZ are buried deep underground.
Understanding Earthquakes in Tennessee
Earthquakes in Tennessee, particularly those from the New Madrid Seismic Zone, are intraplate earthquakes, occurring within a tectonic plate. The NMSZ’s seismic activity is linked to the Reelfoot Rift, an ancient failed rift that formed during the Cambrian Period. This rift, which failed to split the North American continent, remains a zone of weakness deep underground.
Stress accumulates within these ancient zones of weakness, and its release leads to seismic events. Movement occurs along old faults within the Reelfoot Rift due to compressional stress from plate motions. This contributes to the region’s earthquake activity, causing shaking to propagate across wider areas compared to earthquakes in the western United States due to differences in bedrock.
Historical Activity and Current Monitoring
The New Madrid Seismic Zone has a history of significant earthquake activity, notably a series of intense events in 1811-1812. These included three major earthquakes and numerous aftershocks. The main shocks, estimated to be between magnitude 7.2 and 8.2, were the most powerful recorded in the contiguous United States east of the Rocky Mountains. These quakes caused extensive changes to the landscape, including land subsidence, fissures, and the formation of Reelfoot Lake in Tennessee.
The 1811-1812 events caused shaking across a vast area, from the East Coast to the Rocky Mountains. Since 1812, frequent smaller earthquakes have been recorded, with hundreds occurring annually, though most are too minor to be felt. Modern seismic networks continuously monitor these events, providing data that helps identify active faults and understand seismic patterns.
Preparing for Seismic Events
Given the potential for seismic activity, residents in Tennessee can take several steps to enhance their safety. Before an earthquake, secure heavy items such as bookcases, refrigerators, and televisions to walls to prevent them from toppling. Store breakable objects on low shelves to reduce the risk of damage and injury. Develop a family emergency plan, including evacuation routes and a designated meeting point.
During an earthquake, the recommended safety action is “Drop, Cover, and Hold On.” This involves dropping to the ground, taking cover under a sturdy table or desk, and holding on until the shaking stops. If no sturdy furniture is available, crouch against an interior wall and protect your head and neck.
Staying indoors until the shaking subsides is safer, as many injuries occur when people try to exit buildings during active shaking. After the shaking stops, check for injuries, move away from damaged buildings, and be prepared for aftershocks. If trapped, tapping on a pipe or wall can alert rescuers.