Filters: Tags: Frequency domain electromagnetic (X)
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From October 2016 to July 2018, the U.S. Geological Survey, in cooperation with the U.S. Army Corps of Engineers and Maine Department of Transportation, collected surface, marine and borehole geophysical surveys to characterize the subsurface materials on land and under the water at a former mine facility in Brooksville, Maine. Three water-based geophysical methods were used to evaluate the geometry and composition of subsurface materials. Continuous seismic profiling (CSP) methods provide the depth to water bottom, and, when sufficient signal penetration can be achieved, delineate the depth to bedrock and subbottom materials. Continuous resistivity profiling (CRP) and frequency domain electromagnetics (FDEM) methods...
In October 2016 and May 2017 frequency domain electromagnetic (FDEM) methods were used to image the electrical conductivity of the shallow subsurface. Electrical conductivity can be caused by changes in the soil, overburden, saturation, and water quality. Two multi-frequency tools were used at the site. One of the tools has a 1.6-m long antenna that was used in the vertical-dipole mode to collect data in stepped-frequency mode at seven user-selected frequencies ranging from 1530 to 47,970 Hz. The second tool has an antenna that is 2.1 m long, and it was used in vertical dipole mode with five stepped frequencies ranging from 90 to 24,000 Hz. In general, the lower frequencies penetrate to deeper depths, but the data...
In October 2016 and May 2017 frequency domain electromagnetic (FDEM) methods were used to image the electrical conductivity of the shallow subsurface. Electrical conductivity can be caused by changes in the soil, overburden, saturation, and water quality. Two multi-frequency tools were used at the site. One of the tools has a 1.6-m long antenna that was used in the vertical-dipole mode to collect data in stepped-frequency mode at seven user-selected frequencies ranging from 1530 to 47,970 Hz. The second tool has an antenna that is 2.1 m long, and it was used in vertical dipole mode with five stepped frequencies ranging from 90 to 24,000 Hz. In general, the lower frequencies penetrate to deeper depths, but the data...
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