Seismological Research Letters; September/October 2005; v. 76; no. 5;
p. 598-614; DOI: 10.1785/gssrl.76.5.598
© 2005 Seismological Society of America
Quaternary Faulting beneath Memphis, Tennessee
Correspondence: *
Corresponding author
A geologic investigation of the city of Memphis and southern Shelby County,
Tennessee reveals Quaternary faulting. Structure contour maps and
cross-sections of the top of the Pliocene-Pleistocene Upland Complex
(Lafayette gravel), Eocene Upper Claiborne Group, and Eocene Lower Claiborne
Group reveal two 20-m down-to-the-northwest faults that strike approximately
N30°E The western fault is herein called the Memphis Fault and the
eastern, the Ellendale Fault.
The Ellendale Fault is projected to pass beneath the Wolf River flood plain
in east Memphis. At this location, a cut bank exposes flood-plain sands that
are folded into an anticline with a wavelength of 
100 m, an amplitude of
4 m, and a hinge oriented 10°N7°W. The folded sands are truncated
by overlying, flat-lying, clayey silt overbank sediments. A 1-m-wide
earthquake liquefaction sand dike was found above the crest of the anticline,
in the overbank sediments. 14C dates reveal that the folding
occurred between A.D. 390 and 450, and the liquefaction occurred post A.D.
450. Seismic-reflection lines indicate that the fold extends to more than 60 m
depth into the Lower Claiborne Group, has a length of more than 1 km, and is
thus tectonic in origin. The reflection lines also reveal a N25°E
down-to-the-west fault with 5 m of displacement in the Upper Claiborne Group
that we believe is within the Ellendale Fault zone. We believe the anticline
formed during 5 m of Quaternary right-lateral strike-slip movement on the
N25°E-trending fault. Based on these observations, we also believe that
the Ellendale Fault, and perhaps the Memphis Fault, may pose seismic threats
to the city of Memphis and Shelby County, Tennessee.
Copyright © 2009 by Seismological Society of America
