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Papers by Charles McCrackin
I would like to begin by thanking the University of South Florida for giving me the opportunity t... more I would like to begin by thanking the University of South Florida for giving me the opportunity to earn a Master of Science degree in the Department of Geography, Environment and Planning. This thesis has truly been a collaboration of several departments and I would like acknowledge those who have helped to make this document possible. First, I would like to thank my committee chair, Dr. Philip Van Beynen, for giving me the opportunity to work on this project, his supervision and support was vital to the completion of this paper.
This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electri... more This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electrical resistivity surveying (ER) for mapping air-filled karst conduits. Vadose zone caves within the Brooksville Ridge of West Central Florida are relatively similar in architecture, with N-S elongation, and do not consist of an interconnected network of conduits. A high resolution quasi-3D ER survey was performed over two mapped cave systems on the Brooksville Ridge. The resultant survey verified the general effectiveness of quasi-3D ER in locating the two known near-surface cave features. Several other locations in the survey show similar or stronger resistivity anomalies trending in a N-S direction; these are interpreted to represent previously unknown voids. The quality of inversion results were tested by comparing results against the known void locations and by computing cross-over errors from surveys conducted at the same point with different orientations. Our results show that 3D in...
Journal of Cave and Karst Studies
This study assesses the capability and practical applications of quasi-3 Dimensional (3D) Electri... more This study assesses the capability and practical applications of quasi-3 Dimensional (3D) Electrical Resistivity Tomography (ERT) for mapping air-filled conduits in eogenetic karst. A high-resolution quasi-3D ERT survey, consisting of multiple parallel 110m-long 2D profiles, was conducted over two mapped cave systems on the Brooksville Ridge, Florida. The irregularly shaped caves have diameters ranging up to 4 m and span depths from 3 m to 11 m below ground surface. Dipole-dipole array geometries with L2 (least squares) rather than L1 (robust) inversion produced the best fits of resistivity highs with the mapped cave locations. As expected, 3D inversions of sets of parallel lines produced better results than 2D inversions of individual transects. Better imaging was obtained of a cave over which cave-parallel profiles were run in addition to cross-cave profiles. However, even with the best acquisition and processing steps, there are significant misfits in the apparent size of the lar...
I would like to begin by thanking the University of South Florida for giving me the opportunity t... more I would like to begin by thanking the University of South Florida for giving me the opportunity to earn a Master of Science degree in the Department of Geography, Environment and Planning. This thesis has truly been a collaboration of several departments and I would like acknowledge those who have helped to make this document possible. First, I would like to thank my committee chair, Dr. Philip Van Beynen, for giving me the opportunity to work on this project, his supervision and support was vital to the completion of this paper.
This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electri... more This study assesses the capability and practical applications of quasi 3-Dimensional (3D) electrical resistivity surveying (ER) for mapping air-filled karst conduits. Vadose zone caves within the Brooksville Ridge of West Central Florida are relatively similar in architecture, with N-S elongation, and do not consist of an interconnected network of conduits. A high resolution quasi-3D ER survey was performed over two mapped cave systems on the Brooksville Ridge. The resultant survey verified the general effectiveness of quasi-3D ER in locating the two known near-surface cave features. Several other locations in the survey show similar or stronger resistivity anomalies trending in a N-S direction; these are interpreted to represent previously unknown voids. The quality of inversion results were tested by comparing results against the known void locations and by computing cross-over errors from surveys conducted at the same point with different orientations. Our results show that 3D in...
Journal of Cave and Karst Studies
This study assesses the capability and practical applications of quasi-3 Dimensional (3D) Electri... more This study assesses the capability and practical applications of quasi-3 Dimensional (3D) Electrical Resistivity Tomography (ERT) for mapping air-filled conduits in eogenetic karst. A high-resolution quasi-3D ERT survey, consisting of multiple parallel 110m-long 2D profiles, was conducted over two mapped cave systems on the Brooksville Ridge, Florida. The irregularly shaped caves have diameters ranging up to 4 m and span depths from 3 m to 11 m below ground surface. Dipole-dipole array geometries with L2 (least squares) rather than L1 (robust) inversion produced the best fits of resistivity highs with the mapped cave locations. As expected, 3D inversions of sets of parallel lines produced better results than 2D inversions of individual transects. Better imaging was obtained of a cave over which cave-parallel profiles were run in addition to cross-cave profiles. However, even with the best acquisition and processing steps, there are significant misfits in the apparent size of the lar...