Evidence for Large Earthquakes About A.D. 0 and B.C. 1050 in the New Madrid Seismic Zone

Date: 4/24/2019

Time: 06:00 PM

Room: Fifth Avenue

A recent paleoliquefaction study in the New Madrid seismic zone has found evidence for a previously unrecognized large earthquake about A.D. 0 as well as supporting evidence for a previously proposed large earthquake about B.C. 1050. Liquefaction sites that predate the New Madrid paleoearthquakes of A.D. 1450 and A.D. 900 were identified by examining time series of satellite imagery for areas where Late Pleistocene fluvial deposits had been mapped. In addition, liquefaction sites in these areas were examined that occur in association with archaeological sites that predate the Mississippian cultural period (A.D. 800-1673). Two of these sites, Garner and Stiles, located in the southern portion of the seismic zone were selected for detailed archaeological, geophysical, and paleoseismological investigations. Trenches, sited and excavated based on archaeological and geophysical results, exposed sand blows and their feeder dikes and any associated cultural deposits. At the Garner site, earthquake-induced liquefaction features formed circa A.D. 0 +/- 200 yr based on fragments of Synder Cluster projectile points/knives in the upper 0-10 cm of the soil buried by sand blows; radiocarbon dating of organic material in the upper 1.5 cm of the buried soil; and weathering characteristics of the sand blows and feeder dikes including the formation of manganese nodules. At the Stiles site, sand blows and feeder dikes formed circa B.C. 1010, probably during the B.C. 1050 +/- 250 yr New Madrid event, based on radiocarbon dating of the upper 1 cm of the soil buried by the sand blow and supported by weathering characteristics of the liquefaction features including formation of soil lamellae. These findings contribute to the chronology of New Madrid earthquakes and suggest that recurrence times may have varied from about 500 to 1,100 years, that the chronology may not yet be complete prior to A.D. 800, and that the seismic zone has been in an active phase for the past 4,300 years.

Presenting Author: Lorraine W. Wolf

Authors