Filters: Tags: Continuous seismic reflection (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 May 2017 and July 2018, continuous seismic profiling (CSP) surveys were collected in Goose Pond at the Callahan Mine site. The chirp frequency CSP tool was used in the deep water. A tuned transducer (dual-echo sounder) was used in the shallow water, and the data are served separately but within this data release (See CSP-DSO). CSP methods use an acoustic sound source that travels through the water column, reflects off the bottom and sub-bottom layers and is received at the transducer. Using a water column velocity, the two-way travel time can be converted to distance. CSP methods provide the depth to water bottom, and when sufficient signal penetration can be achieved, CSP can be used to delineate the depth and...
In May 2017 a dual-frequency echo sounder was used in Goose Pond at the former Callahan Mine site to obtain seismic profiles in very shallow water. The method uses two fixed transducers mounted in the same housing. One transducer was 24 kHz and the other was 200 kHz. The CSP-DSO data were collected concurrently with continuous resistivity profiling data, and the water bottom was determined with the 200 kHz transducer. The seismic traces on the low frequency transducer were used to analyze the subbottom materials. In some places the signal penetrated the subsurface, but in many places the signal reflected off of a shallow subsurface layer. The data quality was not as good as the swept frequency (chirp) CSP data,...
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