Newly digitized structural data from the southern Appalachians and comparisons to subsurface anisotropy from seismic stations

Abstract:

Seismic anisotropy in rocks is the variation of velocity by the direction of passage of the wave. This phenomenon has the potential to be exploited as an imaging tool for exploring the subsurface structure of a landmass. We investigate this phenomenon and the nature of southern Appalachian seismic fabric, specifically targeting the Greenville 1x2 degree quadrangle which spans the Georgia-South Carolina border and lies within the Blue Ridge and Inner Piedmont. The quadrangle also encompasses the locations of several NSF EarthScope USArray (TA) and Flexible Array (SESAME) seismic stations. Digitization of 4 fabric types from the published geologic quadrangle map (bedding, foliation, lineation, and mylonite) was conducted using GeolMapDataExtractor. Subsets of these data were then selected within a 10 km radius of every seismic station and evaluated using stereonet software and ArcGIS Pro. We compared the strikes of mapped planar fabrics to strikes of dipping subsurface crustal interfaces or foliation as inferred from receiver functions to strikes of hexagonal symmetry planes from modeled seismic anisotropy. We conclude that foliation is the largest fabric contributor to the preserved subsurface geologic structure.