Abstract: Three-Dimensional Hydrogeologic Characterization of Fractured Carbonate Aquifers Using Ground-Penetrating Radar

TSOFLIAS, GEORGIOS P., and JOHN M. SHARP, Jr., Department of Geological Sciences, The University of Texas at Austin, Austin, TX

Three-dimensional characterization of subsurface hydrogeologic properties is very important for understanding groundwater flow and its implications in water resources development, and engineering/environmental studies. Major cities rely on fractured anisotropic carbonate aquifers, such as the Edwards aquifer in Texas. In order to predict threedimensional subsurface fluid flow, fracture network and rock matrix hydraulic properties must be characterized accurately.

Overlapping ground-penetrating radar surveys (one high-resolution threedimensional data volume, regional twodimensional lines and azimuthally varying common mid-point surveys) were collected over a fractured Silurian dolomite aquifer in Door County, Wisconsin. 100 MHz and 200 MHz center frequency surveys provided a depth of investigation of 16 and 12 m, respectively, and vertical resolution in the order of decimeters. The data successfully imaged varying carbonate lithofacies, lithologic discontinuities, and fractures in both the unsaturated and saturated sections of the aquifer. Prominent flow conduits had been identified previously by a dense network of monitoring wells, pump tests and tracer tests. The conduits are clearly identifiable in the groundpenetrating radar data volumes and delineated in threedimensions by distinct continuous reflections.

Ongoing analysis of the presented data sets is investigating ground-penetrating radar signal attribute correlations to subsurface hydraulic properties.

AAPG Search and Discovery Article #90932©1998 GCAGS/GCS-SEPM Meeting, Corpus Christi, Texas