Shallow sounding of crustal regions using electromagnetic surface waves
Article first published online: 7 DEC 2012
Copyright 1986 by the American Geophysical Union.
Volume 21, Issue 5, pages 831–844, September-October 1986
How to Cite
1986), Shallow sounding of crustal regions using electromagnetic surface waves, Radio Sci.,21(5), 831–844, doi:10.1029/RS021i005p00831., and (
- Issue published online: 7 DEC 2012
- Article first published online: 7 DEC 2012
- Manuscript Accepted: 14 APR 1986
- Manuscript Received: 14 NOV 1985
A specific physical interpretation of the effect of relative permittivities εr and conductivities σ upon the amplitude and phase of propagating electromagnetic surface waves is given, where ϵr and σ characterize the layered material regions of a planetary lithosphere. The interpretation is made possible by the availability of simple formulas for the fields of vertical and horizontal unit electric dipoles near interfaces between regions of matter; the earth's lithosphere at its interface with salt water is used as an example. The ranges of εr, σ, frequency ƒ, and radial distance ρ over which the formulas apply are shown to be quite broad. The E1ρ component (the radial electric field in region 1, characterized by complex wave number K1 and adjoined at a planar interface to region 2, characterized by k2, where |k1|2 » |k1|2) is discussed in detail. The attenuation of 20 log10 |E1ρ| as a function of ρ and ρ/δ2, Where δ is the skin depth, is illustrated for conductivity ratios σ2/σ1 = 10−1 to 10−3, over a range of ƒ from 1 Hz to 105 Hz. |E1ρ| is shown to be significant for determining permittivities ε2 at the higher frequencies in this range. The use of |E1ρ| to infer conductivities σ2 at lower frequencies in shallow sounding of the earth's sea floor is discussed in terms of specific lithological and sediment-related parameters. The technology required to transmit and receive 20 log10 |E1ρ| at freshwater and saltwater interfaces with the earth's crust is addressed. A specific experiment is proposed for testing a specialized insulated antenna for seafloor use in shallow coastal waters at 1 kHz.