Estimating equivalent dipole polarizabilities for the inductiveresponse of isolated conductive bodies
Equivalent dipole polarizability matrices and equivalent dipole location are a convenient way to interpret magnetic field data due to currents induced in isolated conductive objects. The uncertainties in polarizability estimates and in equivalent dipole location provide a quantitative measure of the performance of different configurations of transmitters and receivers. These uncertainties are estimated using a linearized inversion (Smith and Morrison, 2002). For many systems, consisting of one or more rectangular loop transmitters and a number of dipole receivers, sited on a horizontal grid, equivalent dipole depth is determined to 10% accuracy to depths approximately 20% deeper, than the depths at which polarizability matrix elements can be determined to the same precision. Systems that have a lower product of rms polarizability uncertainty and square root of their number of transmitter-receiver pairs are considered more effective for the number of transmitter-receiver pairs. Among the systems studied, a system with three orthogonal transmitter loops and a three component receiver is the most effective, for objects shallower than 0.6 times the instrument siting grid spacing, yielding an rms polarizability uncertainty 0.04 times that of a single transmitter single receiver system. At intermediate depths, a system with two vertical component receivers on the diagonal of a square horizontal transmitter loop is most effective for its number of transmitter-receiver pairs, yielding an rms polarizability uncertainty 0.07 times that of a single receiver system. At depths greater than 2.5 times the siting grid spacing a 3 orthogonal loop transmitter with a single vertical component receiver is about the most effective for its number of transmitter-receiver pairs, yielding an rms polarizability uncertainty 0.08 times that of a single transmitter system.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; US Department of the Army under Contract#W74RDV93447299
- DOE Contract Number:
- DE-AC02-05CH11231
- OSTI ID:
- 917338
- Report Number(s):
- LBNL-51573; IGRSD2; R&D Project: 43CC01; BnR: 400403209; TRN: US200816%%530
- Journal Information:
- IEEE Transactions on Geoscience and RemoteSensing, Vol. 41, Issue 6; Related Information: Journal Publication Date: 06/2004; ISSN 0196-2892
- Country of Publication:
- United States
- Language:
- English
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