INVESTIGATIONS OF ELECTRICAL CHARACTERISTICS OF THE SUBSURFACE ROCK MEDIUM IN ESSEX COUNTY, NEW YORK.
Scientific rept. no. 5,
RAYTHEON CO NORWOOD MASS
Pagination or Media Count:
Two vertical drill holes located in Essex County, New York were utilized for measurements to determine the electrical conductivity of the rock media below the surface. Average conductivities in the drill holes were deduced from input impedances of bare monopole antennas placed in the hole. Detailed variations in conductivity with depth in the hole were deduced from short probe measurements. Transmission tests were made between the two drill holes which are separated by a distance of 2.8 miles. In the ELF anf VLF region, transmission of signals were through the rock path between the drill holes. As frequency was increased from the upper region of the VLF band to the mid LF band, the up-over-down mode of propagation became dominant. Where propagation was attributed to the path through the rock, the measured values of mutual impedances between the antennas in the holes were used to deduce the bulk conductivity of the rock path. Measurements of atmospheric noise were also made at one drill hole site to evaluate the refraction loss at the earth-air interface. Author