Ground-Based Time-Domain Electromagnetic Data Collected at Edwards Air Force Research Laboratory, Antelope Valley, California, 2018

Time-domain electromagnetic (TEM) surveys were done northwest of the Air Force Research Laboratory (AFRL) at Edwards Air Force Base. TEM surveys were done at 33 locations between May and October 2018 to refine the understanding of the bedrock-alluvial aquifer transition zone downgradient from the AFRL. TEM surveys (also called transient electromagnetic surveys) provide 1D resistivity soundings of the subsurface, which can be related to lithology and hydrogeology. In the TEM method, electrical current is cycled through a transmitter loop (Tx) wire, which in turn produces a primary magnetic field. When the current is abruptly terminated, a secondary magnetic field 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) at the center of 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 vertical resistivity structure of the earth below the receiver location. Other geophysical techniques, including electrical resistivity tomography and horizontal-to-vertical spectral ratio passive seismic, co-located with the TEM data are made available in other child pages within this data release: https://doi.org/10.5066/P9ZGZTA4. This page contains the TEM data, spatial information for the TEM surveys, and preliminary processed TEM data.