Filters: Tags: {"scheme":"GNIS","name":"brooksville, maine"} (X)
11 results (40ms)|
Filters
Date Range
Types Contacts
Categories Tag Types Tags (with Scheme=GNIS) |
Water levels in Goose Pond were collected while collecting geophysical surveys in May 2017. Three transducers were set to monitor the change in water level associated with tidal changes.
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...
The horizontal-to-vertical spectral ratio (HVSR) method is a passive seismic technique that uses a three-component seismometer to measure the vertical and horizontal components of ambient seismic noise. Seismic noise in the range of ~0.1 to 1 Hertz (Hz) is caused by ocean waves, large regional storms, and tectonic sources. A resonance frequency (f0) is induced in the unconsolidated when there is a substantial contrast (greater than 2:1) in shear-wave acoustic impedance between the overburden and the bedrock. The f0 is determined from the analysis of the spectral ratio of the horizontal and vertical components of the seismic data. The thickness of the overburden can be related to the f0. In general, lower f0 relates...
On May 10, 2017 an electrical resistivity tomography (ERT) profile was collected on the land along the gravel path between the water and the slime impoundment associated with the former mine activities. A total of 56 electrodes, spaced 1 m apart, extended along the base of the slope. Electrode 1 was near monitoring well MW-701 and electrode 56 was near MW-702. In the ERT measurement current is injected through two current electrodes and voltage is measured sequentially across multiple pairs of potential electrodes, which is used to determine the apparent resistivity of the subsurface. In addition, induced polarization (IP) was measured to assess the presence of chargeable layers. Two surveys were collected in dipole-dipole...
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 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 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,...
On May 10, 2017 a land-based seismic survey was collected to obtain a shear- wave velocity (Vs) and compressional velocity (Vp). The Vs was used for estimating with the HVSR data to determine the depth to rock. A secondary objective was to obtain Vs and Vp measurements of the overburden sediments at the toe of the impoundment and adjacent to the stream for geotechnical applications. Four collections were made with a 34.5-m long array of 48 electrodes with one vertical and one horizontal phone every 1.5 m along the survey line. A hammer and two strike plates were used to generate the compressional and shear-wave sound sources.
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...
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. Borehole geophysical logs were collected from May 2-3, 2017 in five boreholes to identify geophysical properties, including the electrical properties and natural gamma emissions. In addition, fluid electrical conductivity and temperature were collected through the water column in the well. Results can be used to identify the water level and the lithologic contacts in the subsurface. Natural...
In May 2017 and July 2018, continuous resistivity profiling (CRP) surveys were collected in Goose Pond at the Callahan Mine site. CRP tool was used to characterize the resistivity of the water column and subbottom layers. For this investigation, 11 electrodes spaced 10 m apart and mounted in a streamer were towed behind the boat. The first two electrodes, closest to the boat, were used to inject current into the water and subbottom materials, and eight electrical potential measurements were made using the remaining nine electrodes in dipole-dipole configuration. With this system, a complete suite of measurements is collected every 2.8 seconds. Because the boat was moving at a slow rate of speed, a complete measurement...
|
|
