Characteristics of near-surface electrokinetic coupling

Beamish, David. 1999 Characteristics of near-surface electrokinetic coupling. Geophysical Journal International, 137 (1). 231-242.

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Naturally occurring electric potentials at the Earth’s surface are traditionally studied using self-potential geophysics. Recent theoretical and experimental work has reinvestigated the manner in which the measurement can be made dynamically using a pressure source. The methodology, often referred to as seismoelectric, relies on electrokinetic coupling at interfaces in the streaming potential coefficient. The ultimate aim of the developing methodologies lies in the detection of zones of high fluid mobility (permeability) and fluid geochemical contrasts within the subsurface. As yet there are no standard methods of recording and interpretation: the technique remains experimental. Field measurements are made using a seismic source and by recording electric voltage across arrays of surface dipoles. This study presents observational characteristics of electrokinetic coupling based on experiments carried out in a wide range of environments. Theory concerning the coupled elastic and electromagnetic wave equations in a saturated porous medium is discussed. It is predicted that coupling will produce electromagnetic radiation patterns from vertical electric dipoles generated at interfaces. Surface- and body-wave coupling mechanisms should provide different time–distance patterns. Vertical electric dipole radiation sources are modelled and their spatial characteristics presented. A variety of experimental configurations have been used, and geometries that exploit phase asymmetry to enhance the separation of signal and noise are emphasized. The main experimental results presented are detailed observations in the immediate vicinity of the source. Simultaneous arrivals across arrays of surface dipoles are not common. The majority of such experiments have indicated that shot- symmetric voltages which display low-velocity moveout are the dominant received waveforms.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: BGS Programmes > Other
Additional Keywords: electrical streaming currents, electrokinetic, electromagnetic, hydraulic transport.
NORA Subject Terms: Earth Sciences
Date made live: 28 Sep 2015 12:33 +0 (UTC)

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