EAST TENNESSEE GEOLOGICAL SOCIETY
  OCTOBER 2016


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.


ETGS HOME

Page updated October 3, 2016