Water-borne towed-transient electromagnetic survey data, along the Ouachita River near Blankston, Louisiana, October 2018
Dates
Publication Date
2022
Time Period
2018-10-21
Citation
Eric A. White, Carole D. Johnson, Ryan F. Adams, Shane J. Stocks, Wade H. Kress, James R. Rigby, and John W. Lane, Jr., 2022, Water-borne towed-transient electromagnetic survey data, along the Ouachita River near Blankston, Louisiana, October 2018: U.S. Geological Survey.
Summary
Water-borne towed transient electromagnetic method, commonly referred to as FloaTEM, was acquired along a single survey track on the Ouachita River during October 2018. During the survey, 39.75 line-kilometers were collected near Blankston, Louisiana study area. Data were collected by members of the U.S. Geological Survey, Hydrogeophysics Branch, and Lower-Mississippi Gulf Science Center and the Aarhus University Hydrogeophysics Group. FloaTEM data acquired along the approximately 40 line kilometers of the Ouachita River in Caldwell County, in Louisiana,were collected to characterize the subsurface resistivity structure in support of a U.S. Geological Survey groundwater investigation of the Mississippi Alluvial Plain. FloaTEM data [...]
Summary
Water-borne towed transient electromagnetic method, commonly referred to as FloaTEM, was acquired along a single survey track on the Ouachita River during October 2018. During the survey, 39.75 line-kilometers were collected near Blankston, Louisiana study area. Data were collected by members of the U.S. Geological Survey, Hydrogeophysics Branch, and Lower-Mississippi Gulf Science Center and the Aarhus University Hydrogeophysics Group. FloaTEM data acquired along the approximately 40 line kilometers of the Ouachita River in Caldwell County, in Louisiana,were collected to characterize the subsurface resistivity structure in support of a U.S. Geological Survey groundwater investigation of the Mississippi Alluvial Plain. FloaTEM data were collected using an Aarhus University HydroGeophysics Group FloaTEM unit using a transmitter loop (Tx) size, 4 by 2 meter square , in an offset-loop receiver (Rx) configuration utilizing a receiver coil that is 0.5 by 0.5 square meters in size (with an effective area of 35 m^2) towed about 7 meters behind the transmitter loop. The transmitter outputs dual currents of about 2.8 and 30 amperes (A) for dual-moment transmission. The Tx measurement cycles takes approximately 0.5 seconds to complete and are comprised of several hundred individual transients. 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. This data release includes the raw and averaged FloaTEM data along the survey line that were used to produce the included final resistivity models not included in this data release. Digital data of the processed soundings are provided and fields are defined in the entities and attributes section of the include XML.
Surface geophysical methods can provide information for the characterization of the subsurface structure of the earth for aquifer investigations. Floating transient electromagnetic (FloaTEM) surveys provide resistivity soundings of the subsurface, which can be related to lithology and hydrogeology. In the floating 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) towed 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.
Preview Image
Water-borne towed-transient electromagnetic instrument known as FloaTEM