Monday,
March 14, 2011
6:00 - 7:30 pm
Pellissippi
State Technical Community College
10915 Hardin
Valley Road, Knoxville
J.L Goins Administration Building, Cafeteria Annex
MARCH PRESENTATION
Evidence for
a 25,000-year History of
Earthquake Activity in Eastern Tennessee
By
Dr. Robert Hatcher, Jr
Department of Earth and Planetary Sciences
University of Tennessee
Knoxville, Tennessee
Abstract
The East Tennessee seismic
zone (ETSZ) is the second most active intraplate region East of
the U.S. Rocky Mountains. But, unlike the New Madrid, MO (AR, TN,
KY), and Charleston, SC, seismic zones, the ETSZ has not had
historical earthquakes of M>5?. It consists of a ~100
km-wide zone of seismicity extending from NE AL and NW GA to just
NE of Knoxville, TN. Wheeler and Crone (USGS)
recently suggested that the ETSZ may be capable of an
"infrequent" M~7.5 shock. Other researchers have
suggested: 1) most earthquakes in the ETSZ are being
produced by sinistral slip on E-W faults and dextral slip on N-
to NE-trending faults from focal mechanisms; 2) seismicity in the
more active central ETSZ occurs within a west-striking,
north-dipping reflective zone associated with seismogenic faults;
and 3) the New York-Alabama lineament along the western limit of
seismicity side of the ETSZ may be related to a major NE-trending
dextral fault and old basement suture.
In this pilot paleoseismic study, we have searched for geologic
evidence that would help clarify the late-Quaternary earthquake
history and potential of the ETSZ. In the region east of
Knoxville, TN, we have identified: 1) strike-slip, thrust,
and normal faulting and regional fracture arrays in
late-Quaternary terraces; 2) minor paleoliquefaction in terrace
alluvium; and 3) anomalous fractured and disrupted features at
three localities attributed to liquefaction and forceful
expulsion of groundwater during one or more major late-Quaternary
earthquakes. Within the Sequatchie River Valley (SRV) along
the southwest margin of the ETSZ, we have identified a zone of
left-stepping, NNW-trending lineaments and nearby fractures in
low terraces; these SRV fractures are currently interpreted to be
of non-paleoliquefaction-but not necessarily
non-paleoseismic-origin. Combined, these new findings imply
that the ETSZ has produced surface faulting and one or more
strong earthquakes during the late Quaternary.
Biographical Sketch
Dr. Hatcher is a distinguished
scientist and professor with the Earth and Planetary Sciences
Dept. at UT where he has served since 1986. He is a structural
geologist who&rsquos primary research goal is to better
understand the evolution of continental crust with particular
interest in the mechanics and kinematics of large faults and the
causes of intraplate seismicity. Dr. Hatcher&rsquos research
has been concentrated in the southern and central Appalachians
but he has studied a number of other mountain chains and
Precambrian continental crust.
Dr. Hatcher received his B.A. and M.S. from Vanderbilt University
and earned his Ph.D. from UT. He began his professional life in
the petroleum industry but has taught most of his career at
several universities including Clemson, Florida State, and
University of South Carolina before joining UT. Dr. Hatcher has
been the recipient of numerous awards including the American
Geological Institute Ian Campbell Medal and Geological Society of
America Penrose Medal.
Page updated May 26, 2018 |