Filters: Tags: Aquifer Characterization (X)
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A suite of geophysical methods was used along the Des Moines River, Beaver Creek, and in the Des Moines River floodplain in Des Moines, Iowa to support the hydrogeologic characterization of the alluvial aquifer associated with the river. The aquifer consists of sands and gravels underlain by weathered shale bedrock. Groundwater from the aquifer along with surface water sources are used for municipal drinking water for the City of Des Moines and surrounding communities. The raw data provided in this data release are minimally processed to filter out erroneous measurements. Data provided in this data release includes continuous resistivity profiling (CRP) and continuous seismic profiling (CSP) that were collected...
In summer 2018, a total of 43 passive seismic surveys were conducted in the Des Moines River floodplain. 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. A resonance frequency (f0) is induced in the unconsolidated deposits 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 to thicker...
Categories: Data;
Tags: Aquifer Characterization,
Des Moines,
Geophysics,
Horizontal-to-Vertical Spectral Ratio,
Hydrogeology,
Electrical resistivity tomography (ERT) surveys were collected in summer 2018 to support hydrogeologic characterization of the alluvial aquifer. For this investigation, 7 surveys were conducted with ERT methods. At each site three surveys were collected, including dipole-dipole (DD), Wenner-Schlumberger (WS), and Inverse Schlumberger (SI )configurations. For each survey a total of 56 electrodes spaced 5-meters (m) apart were used. During 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. Results were combined into a merged dataset. ERT surveys...
Categories: Data;
Tags: Aquifer Characterization,
Des Moines,
Electrical Resistivity Tomography,
Geophysics,
Hydrogeology,
This data release contains geophysical data and well and borehole driller's logs acquired at a small field site in the Llano Uplift of central Texas. The field site is underlain by the unconfined Precambrian Granite Gravel aquifer and the Precambrian Town Mountain Granite bedrock from which the Granite Gravel Aquifer was derived through chemical and mechanical weathering. The data set consists of five types of data in the quantities indicated: (1) 1 time-domain electromagnetic sounding, (2) 441 self-potential measurements, (3) 2 electrical resistivity tomography profiles, (4) 2 seismic refraction tomography profiles, and (5) 4 driller's logs (obtained from 2 wells and 2 shallow boreholes). The data were collected...
In September 2018, approximately 13 miles of continuous seismic profiling (CSP) surveys were collected on the Des Moines River and Beaver Creek in Des Moines, Iowa. The swept frequency (chirp) CSP subbottom profiler was used to characterize the unconsolidated materials above the bedrock. The CSP subbottom profiler is an acoustic sound source that travels through the water column and reflects off the bottom and sub-bottom layers and is received at the transducer. Applying 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 is achieved, CSP can be used to delineate the depth of subbottom layers and topography...
Categories: Data;
Tags: Aquifer Characterization,
Continuous Seismic Profiling,
Des Moines,
Geophysics,
Hydrogeology,
In September 2018, approximately 13 miles of continuous resistivity profiling (CRP) surveys were collected on the Des Moines River and Beaver Creek in Des Moines, Iowa. The CRP method was used to characterize the resistivity of the water column and the underlying geologic materials. Three CRP line profiles were collected during one day of field work and were collected concurrently with continuous seismic profiling (CSP) methods. For this investigation, 11 electrodes spaced 10 m apart and mounted in a streamer were towed behind a manned boat and data were collected using the dipole-dipole array type. The first two electrodes, closest to the boat were used to inject current into the water and river bottom, and eight...
Categories: Data;
Tags: Aquifer Characterization,
Continuous Resistivity Profiling,
Des Moines,
Geophysics,
Hydrogeology,
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