Focal mechanisms for eastern Tennessee earthquakes, 1981-1983

To understand better the faulting process in the Southern Appalachians, eleven single event focal mechanisms (SEFM) and seven composite focal mechanisms (CFM) are determined from 37 events that occurred in eastern Tennessee between September 1981 and July 1983. Both P-wave polarities and (Sv/P)z amplitude ratios are input to a computer program that systematically searches the focal sphere for solutions acceptable within pre-set error limits. Hypocenter locations, azimuth and departure angles are taken from locations obtained by the Tennessee Earthquake Information Center (TEIG) with a four layer velocity model (GCOl). A second velocity model (STEP2), developed to improve focal depth estimates and to acquire continuously varying departure angles, is used to relocate events for which SEFM and CFM solutions are obtained. The two different velocity models produced focal mechanisms with similar nodal plane and P-axis orientations, indicating stable and reliable results; the differences between average strike, dip, and rake angles of the two data sets range from 2° to 11°. Both SEFM and CFM solutions exhibit predominantly strike-slip motion along nearly vertical north-south (right-lateral) or east-west (left-lateral) oriented nodal planes. Standard deviations for average strike, dip, and rake angles are generally less than 20°. P-axis trends average about N50°E, with a nearly horizontal average plunge, and both have standard deviations of 25° or less. Except for three events in the northernmost region, all earthquakes in the study area result from a maximum compressive stress trending between N40°E and N70°E and plunging between 10° and -30°.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Department dc:contributor.department

Geological Sciences

Grantor dc:publisher

Virginia Polytechnic Institute and State University

Year dc:date.issued

1984

Author dc:creator

• Teague, Alan Gaither

Statement dc:rights

• In Copyright

Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

http://hdl.handle.net/10919/88576

OAI identifier oai:identifier

oai:vtechworks.lib.vt.edu:10919/88576