Table 3.

Details of four single-hole and crosshole geophysical imaging methods with potential application to fractured rock. The lateral extent and depth of the surveyed region, and resolution of the measurement, are all typical values for environmental site investigation. The measured parameters can be derived directly from the acquired data. The recovered properties are obtained through processing and/or inversion of the acquired data.

Single-hole and Crosshole Geophysical Imaging Methods	Resolution of Measurement (meters)	Measured Properties	Recovered Parameters of Interest	Potential Fractured-rock Targets
Electrical Resistivity tomography	0.1 to 10	Electrical potential generated by transmission of current	DC electrical conductivity	Fracture zones, Amendment monitoring
Ground Penetrating Radar (transmission tomography)	0.1 to 5	Arrival time and amplitude of transmitted electromagnetic energy	Electromagnetic velocity at antenna frequency (between 60MHz and 250MHz) and attenuation	Major discrete fractures, fracture zones, transport in fractures
Ground Penetrating Radar (reflection)	0.1 to 1	Arrival time and amplitude of reflected electromagnetic energy	Locations and orientations of reflectors	Locations and orientations of discrete fractures
Seismic transmission tomography	1 to 5	Amplitude and arrival time of transmitted elastic energy	Elastic wave velocities, attenuation	Fracture zones, lithology