HR: 0830h
AN: H31B-0473    [PDF]
TI: Anomalous diffusion of electromagnetic fields in the near--surface
AU: * Weiss, C J
EM: cjweiss@sandia.gov
AF: Sandia National Laboratories, Geophysical Technology Dept. PO Box 5800 MS-0750, Albuquerque, NM 85185 United States
AU: Everett, M E
EM: everett@geo.tamu.edu
AF: Texas A&M University, Department of Geology and Geophysics, College Station, TX 77843 United States
AB: Among the various geophysical technologies that have found a niche in shallow subsurface characterization and monitoring is the electromagnetic induction (EMI) method---a method that maps the spatial variability in ground conductivity arising from lithologic changes and the presence of pore fluids. Interestingly, a growing body of evidence suggests that the electrical structure of some geologic materials is inherently fractal, presumed to arise from the dynamical systems that generate and alter the formation and its overlying soil. These observations challenge the applicability of the standard modeling paradigm which rests squarely on the assumption of a spatially smooth (or at least piecewise smooth) distribution of physical parameters within the subsurface. As an alternative, and drawing upon near--surface EMI data recently collected from geologically distinct sites throughout New Mexico and Texas, we investigate the concepts of fractal signals and random walks through spatially-correlated heterogeneous media as a means to describe the observed variations in shallow subsurface EM response. This framework suggests that the diffusion process in geologic media may be described more completely by a modified, fractional--order diffusion equation which is derived from a more generalized form of the standard Maxwell equations.
DE: 0925 Magnetic and electrical methods
DE: 1894 Instruments and techniques
DE: 3250 Fractals and multifractals
DE: 5109 Magnetic and electrical properties
DE: 5139 Transport properties
SC: Hydrology [H]
MN: 2003 Fall Meeting