Impact of earthquake-induced liquefaction and related ground failure on a Mississippian archeological site in the New Madrid seismic zone, central USA

Abstract

An investigation of earthquake-induced liquefaction features and related ground failure at the East archeological site (3PO610) located near the southern end of the New Madrid seismic zone was crucial to the identification of cultural features and horizons and interpretation of archeological data. Through the examination of stratigraphic and structural relations in the archeological excavation as well as in three nearby trenches, it was determined that cultural horizons and features, including the floor of a sweat lodge, are tilted, displaced downward, and buried by a vented sand deposit, known as a sand blow. This sand blow is up to 1 m thick and is composed of four major depositional units, suggesting that it formed during a sequence of large earthquakes. The compound sand blow directly overlies cultural horizons and features, indicating that the earthquakes occurred near the end of or soon after occupation. On the basis of radiocarbon dating of samples collected above and below the sand blow, the earthquakes are estimated to have occurred between A.D. 1300 and 1670. A New Madrid earthquake sequence ca. A.D. 1450 ± 150 was the probable cause of liquefaction and ground failure at the site and may have led to cultural abandonment of the site. Ironically, the earthquakes that may have led to abandonment of the site also helped to preserve it for posterity.