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Application of the modified image method to inversion of synthetic active electromagnetic bathymetric data

Clyde J. Bergeron, Juliette W. Ioup and Gus A. Michel
Application of the modified image method to inversion of synthetic active electromagnetic bathymetric data
Geophysics (June 1987) 52 (6): 794-801

Abstract

A modified image method is used to invert synthetic active electromagnetic data generated from shallow ocean models by means of the exact Sommerfeld theory. The modified image method offers approximate solutions to the Sommerfeld problem: the response of a layered structure of ohmic conductors to an active electromagnetic source. The image plane for the active electromagnetic source is assumed to be at a complex depth given by [Q (sub m) delta (sub 1) exp (-ipi /4)]/(rad)2, where delta (sub 1) is the skin depth of the first layer and Q (sub m) is the multilayer correction factor. Two ad hoc correction factors have been introduced into the modified image method. They bring the image field H (sub I) of the single image at a complex depth into very good agreement with the secondary field H (sub S) of the exact Sommerfeld theory of a two-layer bathymetric model. We demonstrate that these correction factors can be calculated from synthetic data. This allows for an accurate, algebraic, and fast inversion of active electromagnetic data in terms of the parameters of a two-layer model: the conductivities of the sea and sea bottom, and the depth and ohmic skin depth of the sea. The beta factor, which takes into account the departure of the primary active electromagnetic field from a plane wave form at the air-sea interface, is incorporated into the complex two-layer correction function Q (sub m) . A rescaling factor F brings H (sub I) into good agreement with H (sub S) in the depth regime where the beta correction factor is ineffective, i.e., where the first layer depth is greater than two skin depths.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 52
Serial Issue: 6
Title: Application of the modified image method to inversion of synthetic active electromagnetic bathymetric data
Pages: 794-801
Published: 198706
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
Accession Number: 2002-076087
Categories: Applied geophysics
Document Type: Serial
Bibliographic Level: Analytic
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 200223
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