Four closely spaced boreholes were drilled through approximately 20 meters of till into schist bedrock near Mirror Lake, West Thornton, New Hampshire. The site was selected for borehole geophysical research because it is included in a detailed groundwater study where the effects of flow in fractures on flow in overlying drift deposits is being studied. Three of the boreholes are approximately 100 meters in depth, and the fourth is approximately 230 meters in depth. All four boreholes were logged with caliper, acoustic, gamma, single-point-resistivity, and acoustic televiewer logs. Fracture sets dipping approximately 45 degrees to the east were detected in all four boreholes. Two sets of deeper fractures were detected near the bottom of the deepest borehole. Acoustic waveform logs were obtained in all boreholes using three different source frequencies, 34, 15, and 5 kilohertz, for future comparison with surface to borehole seismic data.
Geophysical well log data for study of water flow in fractures near Mirror Lake, West Thornton, New Hampshire