EAST TENNESSEE GEOLOGICAL SOCIETY
March
2011


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.


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