Details of the abstract
Title of paper | Theory and practice of Controlled Source Audio-frequency Magneto-Tellurics: discussion on two case studies in France, at the Rochechouart impact structure and at the Strengbach catchment |
List of authors | P. Sailhac, Y. Quesnel, M. Lajaunie, S. Warden, C. Camerlynck, P. Lambert, J.-P. Malet |
Affiliation(s) |
University of Paris Saclay (France - UMR8148 GEOPS), Aix-Marseille Université (France - UMR730 CEREGE), University of Strasbourg (France - UMR 7063 ITES), Hyperion - France, Sorbone University (France - UMR 7619 METIS), Center for International Research and Restitution on Impacts and on Rochechouart (France - CIRIR), University of Strasbourg (France - UMR 7063 ITES) |
Summary |
Audio-frequency Magneto-Tellurics (AMT) is a passive noninvasive prospecting method; it is based on the electromagnetic induction in the ground from background electromagnetic plane waves caused by far distance sources of natural or anthropic origins; their frequency range is 20 Hz-20 kHz. Controlled Source Audio-frequency Magneto-Tellurics (CSAMT) method is an alternative to AMT which is considered to cope with practical field situations where background anthropic noise from near sources has high amplitudes compared to other incident electromagnetic waves; it is particularly interesting at frequencies in the so-called “AMT-dead band” of low natural activity near 1-3 kHz, corresponding to skin-depth of tens to hundreds of meters. In CSAMT theoretical principles, transmitter must be a set of large electric dipoles (hundreds of meters) located far from the receiver area (tens of km); this geometry is necessary to eventually obtain good estimates of all impedance tensor components. However, actual field situations often impose different configurations. We consider two case studies of CSAMT surveys whose size of the electric transmitter antenna is relatively small (100-300 m). One case is at the Rochechouart impact structure, France (Quesnel et al. 2021); the other one is on the Strengbach catchment, France (Lajaunie et al. 2022). Papers cited above essentially show CSAMT apparent resistivities and their inversion with shallow ERT resistivities; a very few information has been shown concerning the underlying CSAMT questions: Experimental set-up as well as simulation of radiation patterns, data processing, apparent resistivities and inversion will be discussed at EMIW22. |
Session Keyword | 1.0 Instrumentation, sources and data processing |
File upload |
1.0_theory_and_practice_of_co_sailhac.pdf
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