HR: 14:55h
AN: H13G-06    [Abstracts]
TI: Flow-Channeling in Fractured Bedrock: Ground Penetrating Radar Investigations and Interpretation
AU: * Baker, G S
EM: gbaker@geology.buffalo.edu
AF: University at Buffalo, Department of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AU: Talley, J L
EM: jltalley@buffalo.edu
AF: University at Buffalo, Department of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AU: Becker, M W
EM: mwbecker@buffalo.edu
AF: University at Buffalo, Department of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AU: Beyrle, N J
EM: nbeyrle@buffalo.edu
AF: University at Buffalo, Department of Geology 876 Natural Sciences Complex, Buffalo, NY 14260 United States
AB: Recent hydrogeophysical field experiments at a test site in Altona Flats, New York, USA, indicate that surface ground penetrating radar (GPR) can be used to quantitatively examine subhorizontal bedrock bedding plane partitions (fractures) at depth. Quantifiable factors include (1) fracture aperture and (2) variability in fluid salinity within the fracture. To analyze fracture aperture over the 10m x 10m test area, GPR data were collected at stations located every 20 cm in both the x and y direction using 50, 100, and 200 MHz antennas at eight different polarizations each (for a total of 24 "passes" over all the stations). The polarizations at each station included setting the GPR antennas in "parallel broadside" and "parallel endfire" configurations in both the x and y direction (for four total polarizations) and in "cross polarized" orientation at 90 degree intervals of rotation (for the second four polarizations). Thus, a significant amount of complimentary reflection information from the fracture is available for analysis. The innovation therefore includes integrating multiple polarizations of GPR data in 3D to characterize a bedrock fracture. To analyze variability in fluid salinity, the fracture-aperture data were used as background, and a series of additional GPR profiles (generally at 1-m spacing) were collected during various tracer tests. The difference in amplitude between the two datasets therefore can be correlated to changes in fracture fluid salinity because amplitude variations related to aperture are removed. Although other researchers have tracked tracer using GPR, those studies have not been done on horizontal fractures using surface GPR in 3D. The resulting innovation includes estimating tracer geometry (i.e., channeling), velocity, and concentration by integrating fracture aperture information (from GPR) with tracer-related GPR data.
UR: http://www.geophysics.buffalo.edu
DE: 1829 Groundwater hydrology
DE: 1894 Instruments and techniques
DE: 0694 Instrumentation and techniques
DE: 0925 Magnetic and electrical methods
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting