Electrical resistivity tomography (ERT) surveys were done northwest of the Air Force Research Laboratory (AFRL) at Edwards Air Force Base. ERT surveys were done at four locations in May through June of 2018 to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. The ERT technique injects direct-current electricity with known voltage and current into the earth using a series of electrodes and measures the resulting resistivity. This technique is generally limited to investigations of aquifer properties less than 100 meters below land surface. Data from other geophysical techniques co-located with the ERT data, including time-domain electromagnetics and horizontal-to-vertical spectral ratio passive seismic, are made available in other child pages within this data release: https://doi.org/10.5066/P9ZGZTA4. This page contains the ERT data, spatial information for the ERT transects, and preliminary processed ERT data.

The U.S. Geological Survey (USGS) and Air Force Civil Engineering Center (AFCEC) have entered into a cooperative agreement to refine the hydrogeology in the Northeast AFRL and Arroyos groundwater areas of the Air Force Research Laboratory of Edwards Air Force Base. As part of these efforts, two electrical resistivity tomography (ERT) surveys- AFRL9 and AFRL10- were collected in the vicinity of the Mound Fault identified by Cyr and Miller (2022) to better determine the position of these faults. Electrical resistivity tomography is a direct current geophysical method that is used to estimate the subsurface distribution of the electrical resistivity (measured in ohm-meters; ohm-m) of a material, and is based on the assumption that measured electric potentials (voltages) near current carrying electrodes are influenced by the electrical resistivities of the underlying material (Zohdy and others, 1974; Loke, 2000). ERT is a popular technique for subsurface investigations because it is based on simple physical principles and for its efficient data acquisition (Dahlin and Zhou, 2004). A combination of the Dipole-Dipole and Strong Gradient arrays was used for this survey and combined to create an optimized dataset (Stummer and others, 2004). The Dipole-Dipole array type yields a high precision dataset, particularly of vertical structures, but can exhibit lower signal to noise ratios (Dahlin and Zhou, 2004; Binley and Kemna, 2005), while the Strong Gradient array provides more complete spatial coverage, and high signal to noise ratio with increased acquisition efficiency (Dahlin and Zhou, 2004; Dahlin and Zhou, 2006, Advanced Geosciences Inc., 2009).

The U.S. Geological Survey (USGS) and Air Force Civil Engineering Center (AFCEC) have entered into a cooperative agreement to refine the hydrogeology in the Northeast AFRL and Arroyos groundwater areas of the Air Force Research Laboratory of Edwards Air Force Base. As part of these efforts, two electrical resistivity tomography (ERT) surveys- AFRL9 and AFRL10- were collected in the vicinity of the Mound Fault identified by Cyr and Miller (2022) to better determine the position of these faults. Electrical resistivity tomography is a direct current geophysical method that is used to estimate the subsurface distribution of the electrical resistivity (measured in ohm-meters; ohm-m) of a material, and is based on the assumption that measured electric potentials (voltages) near current carrying electrodes are influenced by the electrical resistivities of the underlying material (Zohdy and others, 1974; Loke, 2000). ERT is a popular technique for subsurface investigations because it is based on simple physical principles and for its efficient data acquisition (Dahlin and Zhou, 2004). A combination of the Dipole-Dipole and Strong Gradient arrays was used for this survey and combined to create an optimized dataset (Stummer and others, 2004). The Dipole-Dipole array type yields a high precision dataset, particularly of vertical structures, but can exhibit lower signal to noise ratios (Dahlin and Zhou, 2004; Binley and Kemna, 2005), while the Strong Gradient array provides more complete spatial coverage, and high signal to noise ratio with increased acquisition efficiency (Dahlin and Zhou, 2004; Dahlin and Zhou, 2006, Advanced Geosciences Inc., 2009).

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.

The U.S. Army Fort Irwin National Training Center (NTC), approximately 35 mi north-northeast of Barstow, California, covers approximately 1,177 square miles, and is comprised of ten groundwater basins, three of which have been subdivided into subbasins on the basis of additional hydrologic testing. Since the early 1990s, the U.S. Geological Survey (USGS) has been studying water resources issues at Fort Irwin. One issue of concern is the potential effect of groundwater development resulting from planned training expansion and infrastructure at the NTC on natural springs and seeps, an important water source for wildlife. In 2010, the USGS entered into cooperative agreements with the U.S. Army to complete studies of groundwater resources focusing primarily on undeveloped basins within the NTC. Electrical resistivity data were collected in 2015 and 2017 at three groups of springs in undeveloped basins in order to quantify the spatial extent of groundwater associated with each spring and to detect hydrologic change over this two year time period. In 2017, electrical resistivity data were also collected at the airstrip on Bicycle Lake (a dry lakebed) to provide insight on ground failures and data regarding the depth of the known surface cracks and macropolygon features.