Monday,
October 10, 2016
6:00 - 7:30 pm
Pellissippi State
Technical Community College
10915 Hardin Valley Road, Knoxville
J.L Goins Administration Building, Faculty-Staff Dining Room
OCTOBER PRESENTATION
What We know about the Eastern Tennessee Seismic Zone
Paleo-Seismicity After 8 Years of Research—Tip of the
Iceberg
By
Dr. Robert D. Hatcher, Jr.
UT Distinguished Scientist & Professor
Department of Earth and Planetary Sciences
and Science Alliance Center of Excellence
Knoxville, Tennessee
Abstract
The eastern Tennessee seismic
zone (ETSZ) is the second most active and second largest areally
in the eastern US after New Madrid, extending from NE AL across
TN into SE KY. Despite its activity and size, no historic
earthquakes of Mw>4.8 have occurred here. Our goal is to
identify the largest paleo-earthquakes, and establish their
recurrence interval. We have concentrated on Quaternary river
sediments up to 800 ka resting on Paleozoic shale bedrock to
eliminate Quaternary karst features formed on carbonate rocks. We
have discovered numerous fractures and several 1-2 m-displacement
faults filled with red sandy clay that displace bedrock shale and
Quaternary river deposits. These faults occur along a >80 km
linear trend from Vonore, TN, (057 moderately SE-dipping thrust
and 070 steeply SE-dipping normal faults) to near Alcoa, TN, (060
moderately SE-dipping thrust) to Dandridge, TN (050 moderately to
near-flat, SE-dipping listric thrust). Most faults occur along an
060 linear trend (parallel to a local trend of maximum
seismicity), with one small, steeply dipping group near Tellico
Plains, TN (005 steeply W- and E-dipping), located along an
almost N-S seismicity alignment. All thrust faults have a NE
trend and are top-to-the-NW, oblique to regional bedrock strike;
the normal fault may be a part of a local thrust-strike-slip
stepover system.
The 060 linear fault trend, if part of a common system that
produced the surface ruptures, may be connected in either a
NE-striking master fault at depth and more widespread red sandy
clay-filled fractures, or an array of localized coseismic faults
and widespread fractures that developed above an active basement
fault. Either option is very likely the product of one or more
Mw>7.0 earthquakes; taken separately they would require one or
more earthquakes of Mw>6.5 in the ETSZ to produce the observed
displacements. Our current data suggest a recurrence interval of
<7,500 y; this data set, however, is incomplete.
Biography
Dr. Robert D. Hatcher, Jr. is currently a Distinguished Scientist and Professor with the University of Tennessee in Knoxville, Tennessee. Dr. Hatcher's primary research goal is to gain a better understanding of the evolution of continental crust, mostly through the study of mountain chains and mature crust. Most of his research has been concentrated in the southern and central Appalachians, but large amounts of time have been spent visiting and studying other mountain chains, and Precambrian continental crust. His primary interest is in the mechanics and kinematics of large faults, which formed a natural transition into related long-term interests in the geologic controls of petroleum occurrence in the Appalachians, radioactive waste management, the causes of intraplate seismicity and geologic evidence for determination of recurrence intervals for intraplate earthquakes.
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