Controlled-source audio magnetotellurics (CSAMT) is a grounded electromagnetic imaging technique used primarily in the mining industry and is closely related to the marine controlled-source electromagnetic method (mCSEM) which is more familiar to the oil and gas community. In both methods, electric currents are injected into the Earth using long transmitter dipoles and electric and magnetic measurements are made at an array of stations. Historically, CSAMT data have been interpreted using readily available MT modelling algorithms and including only far-field data in the interpretation. In this work, we demonstrate the advantages of carrying out complete-earth, three-dimensional modelling of all grounded dipole EM fields, including those near the source, and avoiding commonly employed, adhoc methods that discard otherwise valuable near-field data that are unusable in MT-only modelling workflows.

Open-Access Online Publication: May 29, 2023