데이터셋 상세
미국
Floating Electromagnetic Surveys from the Lower Delaware River Basin
Electromagnetic (EM) geophysical methods provide information about the bulk electrical conductivity of the subsurface. EM data has been widely used to investigate aquifers and geologic structures. In the following study, the United States Geological Survey conducted a boat-towed, waterborne transient electromagnetic (FloaTEM) survey to examine conductivity within the subsurface of the main Delaware River channel and the Leipsic River. The Leipsic River flows through an estuary into the Delaware Bay. Subsurface conductive zones, when viewed in the context of the regional conceptual model and other data, can help determine the likely groundwater location of the freshwater/saltwater interface within the Delaware River, as well as key hydrogeological layers such as the Lower Potomac-Raritan-Magothy Aquifer within the Northern Atlantic Coastal Plain Aquifer System, and their connectivity with the riverbed. Permeable aquifers could provide a hydraulic connection between surface water and inland groundwater. Therefore, changes to river water salinity could have an accelerated impact on water pumped from wells inland that are connected via these permeable aquifers. The FloaTEM system transmits a primary electrical current through a transmitter loop (Tx) wire. This creates a static primary magnetic field. Then, the current in the TX loop is subsequently turned off, resulting in secondary electrical currents being induced in the earth. These induced electrical currents decay with time, and this rate of decay in the secondary electrical field is a function of the bulk conductivity of the subsurface material. As the secondary electrical field decays, a secondary magnetic field is induced and measured at a receiver (Rx) loop towed behind the Tx loop. The Rx loop measures the decay of the secondary magnetic field as a function of time (dB/dt). Measured dB/dt decay curves can be inverted to recover the depth-dependent resistivity structure of the earth. FloaTEM surveys were conducted downstream from Wilmington, DE on 8/26/2020 and 8/27/2020. Data from 8/26/2020 were collected around the Augustine Wildlife Area boat ramp, and data on 8/27/2020 were collected near the Collins Landing boat ramp. FloaTEM surveys were again conducted downstream from Wilmington, DE on 8/25/2021 and 8/26/2021. Data from 8/25/2021 were collected upstream of the 2020 surveys around the Pennsville public boat ramp, while data on 8/26/2021 were collected near the Collins Landing boat ramp and covered a similar area as the 2020 data. Data collected in 2021 also included a section of the Delaware River further upstream near Philadelphia PA, collected on 8/24/2021 and made use of the Fort Mifflin boat ramp. A final back and forth profile in the Leipsic River within the Bombay Hook National Wildlife Refuge (estuary) was gathered on 8/27/21, and used the Port Mahon Boat Launch as the starting/ending point. Surface water specific conductance data were also collected during portions of the surveys.
데이터 정보
연관 데이터
Floating and Towed Transient Electromagnetic Surveys used to Characterized hydrogeology underlying Rivers and Estuaries: March to December 2018
공공데이터포털
Surface and water-borne geophysical methods can provide information for the characterization of the subsurface structure of the earth for aquifer investigations. Floating and towed transient electromagnetic (FloaTEM and tTEM) surveys provide resistivity soundings of the subsurface, which can be related to lithology and hydrogeology. In the TEM method, electrical current is cycled through a wire in a transmitter loop (Tx), which in turn produces a static magnetic field. When the current is abruptly terminated, an instantaneous current is induced in the earth, and it moves downward and outward as the induced current decays with time. The decay is controlled by the resistivity of the earth. A receiver (Rx) pulled behind the Tx loop measures the secondary magnetic field as a function of time (dB/dt). Decaying voltage measurements at the receiver are converted to apparent resistivity, which can be inverted to recover the depth-dependent resistivity structure of the earth. FloatTEM surveys were conducted at four locations on the Eel River near Falmouth, Massachusetts,on the Rainbow Reservoir near Windsor, Connecticut, on the Upper Delaware River near Barryville, New York, and on the Tallahatchie River in Shellmound, Mississippi. A tTEM survey was collected adjacent to the Tallahatchie River in Shellmound, Mississippi. The data collected at each site are provided as separate datasets. This data release includes the averaged, culled and inverted TEM data showing resistivity (in ohm-meters) with depth for each of the survey sites.
Floating transient electromagnetic (FloaTEM) surveys in the Eel River near Falmouth, Massachusetts
공공데이터포털
Floating transient electromagnetic (FloaTEM) data were acquired on the Eel River during November 2018. During the survey, approximately 1.6 line-kilometers were collected in the Eel River, Falmouth, Massachusetts study area. Data were collected by members of the U.S. Geological Survey, Hydrogeophysics Branch, and New England Water Science Center. FloaTEM data acquired along the Eel River in Barnstable County, in Massachusetts, were collected to test a new continuous water-borne transient electromagnetic data collection platform, and to characterize the subsurface resistivity structure in support of a U.S. Geological Survey groundwater investigation of the Falmouth, Massachusetts area. FloaTEM data were collected using an Aarhus University HydroGeophysics Group FloaTEM unit using a transmitter loop (Tx) size, 4 by 2 meter square (m^2), in an offset-loop receiver (Rx) configuration utilizing a receiver coil that is 0.5 by 0.5 m^2 in size (with an effective area of 35 m^2) towed about 7 meters behind the Tx loop. The Tx outputs dual currents of about 3 and 30 amperes (A) for dual-moment transmission. The measurement cycles take approximately 0.5 seconds to complete and are comprised of several hundred individual transients that are averaged into 1D soundings along the profile. This data release includes the averaged, culled, and inverted FloaTEM data along the survey line that were used to produce the final resistivity models. Digital data of the processed soundings are provided, and fields are defined in a data dictionary. (1) Files with *AVERAGED.xyz and *AVERAGED.csv are space- and comma-delimited ASCII files that contain the least processed data where transients were averaged together and most coupled data were removed.Data locations are provided as UTM Zone 15 N projection and datum of WGS-84. (2) Files with *CULLED.xyz and *CULLED.csv are space- and comma- delimited ASCII files containing the processed data where negatively-impacted transients and coupled data were removed using a combination of automated and manual processing. Data locations are provided as UTM Zone 15 N projection and datum of WGS-84. (3) Files with *INVERTED.xyz and *INVERTED.csv are space- and comma-delimited ASCII files containing the inversion model results. Model locations are provided as UTM Zone 15 N projection and datum of WGS-84. (4) Files with *WATER-DEPTH_DATA.xyz and *WATER-DEPTH_DATA.csv are space- and comma-delimited ASCII files containing the water-depth data as measured from the bottom of the transducer. Water-depth measurement locations are provided as UTM Zone 15 N, WGS-84. (5) Files with *INVERTED_image.png and *INVERTED_image.pdf are the inverted model output as a 2D profile of electrical resistivity distribution in the subsurface.
Floating Transient Electromagnetic Survey Data from the Columbia River near Hanford, WA
공공데이터포털
This data release contains motorboat-towed floating transient electromagnetic data collected from the Columbia River near Hanford WA. Data were collected using a ~16 foot (4.9 meters) outboard motorboat during two field campaigns: July 2021 and April 2022. In total, several hundred linear kilometers of data were collected from a reach of the Columbia that extends from approximately Vernita Bridge to Richland, WA with some additional data collected in the Horn area north of White Bluffs in April 2022. An Aarhus Geoinstruments FloaTEM system was used to collect these data. The depth of investigation of the FloaTEM system is variable but ranged from approximately 50 to 100 meters. Previously collected high-resolution bathymetric data and observed specific conductance of the water column were used to constrain water depth and resistivity in the processing and interpretation of results.
Frequency domain electromagnetic induction (EMI) data collected within and adjacent to the Little Wind River, Riverton, WY, USA
공공데이터포털
The electrical conductivity of the earth is used to help infer lithological and pore fluid properties. Various geophysical methods can provide estimates of the distribution of below ground electrical conductivity, with each method having certain limitations. This data release presents raw and processed results from land-based and water-based frequency domain electromagnetic induction (EMI) data collected from August 23, 2017 to August 28, 2017. The raw data consist of .csv files from the Geophex GEM-2 unit. Data were primarily collected by walking with the instrument at approximately 1 m off the ground in horizontal coplanar (ski flat) mode. A survey along a section of the Little Wind River in a kayak (with about 0.3 m of elevation above the water surface) was also collected.
Fluid electrical conductivity data
공공데이터포털
When water is pumped slowly from saturated sediment-water inteface sediments, the more highly connected, mobile porosity domain is prefferentially sampled, compared to less-mobile pore spaces. Changes in fluid electrical conductivity (EC) during controlled downward ionic tracer injections into interface sediments can be assumed to represent mobile porosity dynamics, which are therefore distinguished from less-mobile porosity dynamics that is measured using bulk EC geoelectrical methods. Fluid EC samples were drawn at flow rates similar to tracer injection rates to prevent inducing preferential flow. The data were collected using a stainless steel tube with slits cut into the bottom (USGS MINIPOINT style) connected to an EC meter via c-flex or neoprene tubing, and drawn up through the system via a peristaltic pump. The data were compiled into an excel spreadsheet and time corrected to compare to bulk EC data that were collected simultaneously and contained in another section of this data release. Controlled, downward flow experiments were conducted in Dual-domain porosity apparatus (DDPA). Downward flow rates ranged from 1.2 to 1.4 m/d in DDPA1 and at 1 m/d, 3 m/d, 5 m/d, 0.9 m/d as described in the publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W., 2018, Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.
Water-Based Frequency Domain Electromagnetic Surveys at the Callahan Mine Superfund Site in Brooksville, Maine: October 2016 to May 2017
공공데이터포털
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-meter (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 Hertz (Hz). The GEM2HG 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 are an average over a larger volume; whereas higher frequencies penetrate only to shallow depths but provide a smaller volume-averaged measurement. A plastic-pipe frame was used to keep the antenna at a fixed distance of 1.0 m above water surface to minimize noise induced by variation in tool position. Profiling data were collected at walking speeds of approximately 3 kilometer per hour(km/hr), with a full suite of seven frequencies measured every 0.5 seconds (s), which translates to a complete measurement suite about every 0.4 m along the profile. All measurement positions were mapped with a global positioning system (GPS). Both the primary and secondary fields were measured at the receiver coil, and the ratio of the secondary to primary magnetic fields was recorded as in-phase and quadrature. The in-phase part of the EM field relates to the magnetic susceptibility, and the quadrature component relates to apparent conductivity (aEC) . Raw data for each frequency and Q Sum (a summation of quadrature values) were recorded in parts per million (ppm). In post processing, EM data were converted to magnetic susceptibility and aEC, which can be inverted to get the actual depth of the electrical conductivity value. This data release provides the raw ppm values, the magnetic susceptibility, and the apparent electrical conductivity values.
Bulk electrical conductivity data
공공데이터포털
Tracking changes in bulk electrical conductivity (EC) during tracer tests in saturated sediments allows for direct observation of both mobile and less-mobile pore space exchange dynamics. Electrode arrays made up of four stainless steel rods (insulated with the exception of exposed 0.5 cm tips) were installed vertically at depths of interest and apparent electrical resistivity data (the inverse of bulk EC) were collected using a Wenner configuration with an AGI SuperSting R8 meter. The Bulk EC data are described and listed within the files below. Controlled, downward flow experiments were conducted in Dual-domain porosity apparatus (DDPA). Downward flow rates ranged from 1.2 to 1.4 m/d in DDPA1 and at 1 m/d, 3 m/d, 5 m/d, 0.9 m/d as described in the publication: Briggs, M.A., Day-Lewis, F.D., Dehkordy, F.M.P., Hampton, T., Zarnetske, J.P., Singha, K., Harvey, J.W. and Lane, J.W., 2018, Direct observations of hydrologic exchange occurring with less-mobile porosity and the development of anoxic microzones in sandy lakebed sediments, Water Resources Research, DOI:10.1029/2018WR022823.
Water-borne electromagnetic induction data collected at Hen Cove, Pocasset, Massachusetts, 2022
공공데이터포털
The bulk electrical conductivity of the subsurface was indirectly measured with electromagnetic imaging (EMI) by using induced secondary electromagnetic signals generated by subsurface electrical conductors in response to transmitted electromagnetic energy (Zohdy and others, 1974). Electromagnetic induction data were collected using a DUALEM-421 (DualEM, Inc.) mounted on an inflatable stand-up paddle board about 15 centimeters above the water surface. The DUALEM-421 uses 3 transmitter-receiver coil spacings (4-, 2-, and 1-meters) and 2 orientations (vertical dipole, and horizontal dipole). Larger coil spacings interrogate a larger/deeper sampling volume than smaller coil separations. REFERENCE: U.S. Geological Survey, Techniques of Water-Resources Investigations, Book 2, Chapter D1, Zhody, A. A. R., Eaton , G. P., and Mabey, D. R. https://doi.org/10.3133/twri02D1
Transient Electromagnetic Surveys Collected for Delineation of Saline Groundwater in the Genesee Valley, New York, October-November 2016
공공데이터포털
In late October and early November 2016, transient electromagnetic (TEM) data were acquired at two locations in Livingston County, in western New York, in order to characterize the subsurface resistivity structure in support of a U.S. Geological Survey groundwater investigation. The TEM data were collected as part of a pilot project to evaluate geophysical methods to characterize the valley-fill sediments, underlying bedrock, and salinity of the subsurface. TEM data were collected using an ABEM WalkTEM unit (acquisition software V 1.1.0) using a 100 by 100 meter square transmitter loop (Tx), a center-loop receiver (Rx) that is 0.5 by 0.5 square meters in size (with an effective area of 35 m^2), and dual currents of about 2 and 11 amperes (A). In addition, a second center-loop receiver, 10 by 10 meter square in size (with an effective area of 1400 m^2) was used. Both receivers were centered and concentrically nested inside. The Tx Measurement cycles were stacked 10 times, and 2-3 measurements were taken at each site. Multiple surveys collected at the same location were stacked, filtered, and averaged for each Tx current and set of Rx measurements. This data release includes the raw and processed TEM data and inverted soundings showing resistivity (in ohm-m) with depth at both of the survey sites.
목록