A STATISTICAL-ANALYSIS OF EARTHQUAKE FOCAL MECHANISMS AND EPICENTER LOCATIONS IN THE EASTERN TENNESSEE SEISMIC ZONE

The location and orientation of possible seismogenic basement faults i n the eastern Tennessee seismic zone is studied using information prov ided by focal mechanisms and the location of earthquake epicenters. Tw enty-six well-constrained focal mechanism solutions are derived using a new velocity model and relocated hypocenters, The results suggest th at strike-slip motion on steeply dipping planes is the dominant mode o f faulting throughout the 300-km-long,a seismic zone, Most of the mech anisms can be grouped into two populations, The larger population is c haracterized by steeply dipping N-S- and E-W-striking nodal planes wit h right-lateral and left-lateral slip, respectively, The second popula tion differs from the first by an approximate 45 degrees eastward rota tion about the B axis. An analysis of the distribution of azimuths bet ween epicenters was conducted, The frequency distribution of intereven t azimuths shows significant clustering in the northeasterly and easte rly directions, for interevent epicentral distances less than 30 km. T hose directions represent the most often observed nodal plane orientat ions and are interpreted as the dominant strike directions of seismoge nic basement faults, The locations of potential faults are inferred on the basis of statistically significant alignments of juxtaposed epice nters and correlation with focal mechanisms, The results suggest a ser ies of northeast-trending, en-echelon basement faults, intersected by several east-trending faults, Most of the larger magnitude, instrument ally located, earthquakes in the seismic zone occurred in proximity to the statistically identified potential faults.