Layering within the dike and sill indicate that they formed during two or more events. Public domain. Venting of large quantities of water, sand, and mud as a result of liquefaction could flood fields and roads and disrupt agriculture for weeks to months. It is the most seismically active area of the United States east of the Rockies. )Earthquake chronology for New Madrid seismic zone from dating and correlation of liquefaction features at sites (listed at top) along NE-SW transect. Memphis has an aging infrastructure, and many of its large buildings, including unreinforced schools and fire and police stations, would be particularly vulnerable when subjected to severe ground shaking. to 1000 A.D. and 800 to 1670 A.D., respectively. While not as well known for earthquakes as California or Alaska, the New Madrid Seismic Zone (NMSZ), located in southeastern Missouri, northeastern Arkansas, western Tennessee, western Kentucky and southern Illinois, is the most active seismic area in the United States, east of the Rocky Mountains.
)Although there are uncertainties regarding their age ranges, certain pottery and point types, as well as plant remains, are considered diagnostic of various cultural periods.
KAIT – In the last two weeks, the U.S. Geological Survey recorded 20 earthquakes along the New Madrid fault line. )Photograph of some diagnostic artifact types in New Madrid region: 1, Campbell Appliqué; 2, Bell Plain; 3, Nodena Elliptical point; 4, Nodena Banks variety point; 5, Parkin Punctate; 6, Madison point; 7, Varney Red Filmed; 8, Barnes Cord Marked; 9, daub with wattle impression. In eastern North America, where near-surface faulting is uncommon or difficult to identify, paleoseismology often employs liquefaction features to learn about prehistoric earthquakes.
Sand blow buries soil that was at ground surface at time of event. It was located about 2 miles east-northeast of Ridgely, Tenn., Diagnostic artifacts found in association with sand blows provide a preliminary estimate of the age of the causative earthquake.
Although Memphis is likely to be the focus of major damage in the region, St. Louis, Mo., Little Rock, Ark., and many small and medium-sized cities would also sustain damage.The geologic record of repeated large earthquakes, the historical accounts of the 1811-12 large earthquakes, and the continuing earthquake activity in the area are compelling evidence that the New Madrid region has high earthquake hazard. Inferred timing of events is shown with colored bands.
Failure of levees, especially during high water, would contribute to flooding, and failures of riverbanks could make the Mississippi River and its tributaries difficult to navigate for many weeks.The City of Memphis and the surrounding metropolitan area of more than one million people would be severely impacted. Similarly, plant remains and other organics found in cultural horizons can be used to date associated sand blows. Flood deposits bury other sand blows. Magnitude estimates and epicenters are based on interpretations of historical accounts and may vary. If the pore-water pressure increases to the point that it equals the weight of the overlying soil, the sediment liquefies and behaves as a fluid. Some sites show age estimates for more than one feature related to different events (e.g., Eaker 2 and L2).