Use of Directional Borehole Radar and Azimuthal Square‐Array D.C. Resistivity Methods to Characterize a Crystalline‐Bedrock Aquifer

Geology and ground-water resources of the Lawrenceville area, Georgia

“…Fractures intersecting the borehole in bedrock wells were identified using an integrated suite of borehole geophysical logsincluding caliper, focused resistivity, long-and shortnormal resistivity, gamma, acoustic televiewer and velocity, spontaneous potential, fluid temperature and resistivity, deviation, heat-pulse flowmeter, video camera logs, and single-borehole radar surveys. As part of the local studies, subsequent to fracture zone identification, the orientation of fractures within each zone was interpreted from acoustic televiewer logs and directional borehole radar surveys (Chapman and Lane, 1996).…”

Geophysical investigations of well fields to characterize fractured-bedrock aquifers in southern New Hampshire

“…Whereas fracture zones were correlated with photolinear features in some settings by geophysical methods, for example in karst environments in Florida (Spratt, 1996) and in sandstones in West Africa (Taylor and others, 1999), few publications document the use of geophysical techniques for investigation of water supply in fractured crystalline rock, particularly in the northeastern United States. Previous investigations using various geophysical methods to study highyield crystalline bedrock aquifers include those of Chapman and Lane, 1996;Mack and others, 1998;and Johnson and others, 1999. Direct-current resistivity and borehole radar techniques were used by Chapman and Lane (1996) to determine the orientations of fracture zones in a crystalline bedrock aquifer in Lawrenceville, Ga. Advanced borehole techniques were used in Rye, N.H., to identify fractures in wells and in the surrounding area.…”

“…Previous investigations using various geophysical methods to study highyield crystalline bedrock aquifers include those of Chapman and Lane, 1996;Mack and others, 1998;and Johnson and others, 1999. Direct-current resistivity and borehole radar techniques were used by Chapman and Lane (1996) to determine the orientations of fracture zones in a crystalline bedrock aquifer in Lawrenceville, Ga. Advanced borehole techniques were used in Rye, N.H., to identify fractures in wells and in the surrounding area. Strikes of fracture sets in the wells in Rye, identified by Johnson and others (1999), were coincident with remotely sensed lineaments identified by Ferguson and others (1997).…”

Azimuthal Resistivity to Characterize Fractures in a Glacial Till

“…It is generally assumed that the anisotropy is caused by the presence of fluid-filled fractures in a relatively resistive rock or soil. Azimuthal resistivity has been used to determine fracture geometry in crystalline rocks and glacial till by Lane et al (1995), Carlson et al (1996 a and b), Hansen and Lane (1996), Chapman and Lane (1996), Lane et al (1996), and Baker and McIntyre (2001). Hansen and Lane (1996), also characterize the porosity and aperture of high-angle fractures using the azimuthal resistivity method.…”