Continuous profiling of magnetotelluric fields

Thesis/Dissertation · Wed May 01 04:00:00 EDT 1991

DOI:https://doi.org/10.2172/5903983· OSTI ID:5903983

Verdin, Carlos Torres ^[1]

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1. Univ. of California, Berkeley, CA (United States)

The magnetotelluric (MT) method of mapping ground electrical conductivity is traditionally based on measurement of the surface impedance at widely spaced stations to infer models of the subsurface through a suitable pseudo 1-D inverse or with linearized least-squares inversion for 2- or 3-D geoelectric media. It is well known that small near-surface inhomogeneities can produce spatial discontinuities in the measured electric fields over a wide frequency range and may consequently bias the impedance on a very local scale. Inadequate station spacing effectively aliases the electric field measurements and results in distortions that cannot be removed in subsequent processing or modelling. In order to fully exploit the benefits of magnetotellurics in complex geological environments, closely spaced measurements must be used routinely. This thesis entertains an analysis of MT data taken along continuous profiles and is a first step that will allow more encompassing 2-D sampling techniques to become viable in the years to come. The developments presented here are to a large extent motivated by the physical insight gained from low-contrast solutions to the forward MT problem. These solutions describe the relationship between a perturbation in the electrical conductivity of the subsurface and the ensuing perturbation of the MT response as the output of a linear system. Albeit strictly accurate in a limited subset of practical exploration problems, the linearized solutions allow one to pursue a model independent study of the response characteristics of MT data. In fact, these solutions yield simple expressions for 1-,2-, and 3-D resistivity models which are here examined in progressive sequence.

• Research Organization: Lawrence Livermore National Lab., CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States). Office of Energy Research
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5903983
• Report Number(s): LBL-31334; ON: DE92003897
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
BORN APPROXIMATION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRICAL SURVEYS
ELECTROMAGNETISM
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
MAGNETISM
MAPPING
PHYSICAL PROPERTIES
SURVEYS
TELLURIC SURVEYS