HR: 15:10h
AN: NS13A-07 INVITED    [Abstracts]
TI: A Description of Seismo-electric and Electro-seismic Coupling
AU: * Pride, S R
EM: srpride@lbl.gov
AF: Lawrence Berkeley National Lab, 1 Cyclotron Road, MS 90-1116, Berekely, CA 94720, United States
AB: In this invited overview, the basic mechanisms involved in seismo-electric and electro-seismic coupling are presented. The coupling mechanism is electrokinetic, meaning it is due to the nanoscale charge separation present at the water/mineral-grain interface inside of rocks and soils. Two types of seismo-electric response may be distinguished: (1) the electric field contained within a seismic wave and that moves along with the wave as part of the material response but that has no support outside the seismic wave; and (2) the electric field generated when a seismic wave traverses an interface, resulting in the symmetry of the charge separation within the wave to be broken, thus creating a far field quasi-static electric field that falls off like a dipole. It is the interface response that allows interfaces within the earth to be imaged. In electro-seismic response, a quasi-static electric field is established by injecting a time-varying current into the earth. This electric field drives a fluid flow via electro-osmosis. Where the electric field traverses an interface, more fluid may be driven into the interface from one side than can be removed from the other side. This results in fluid accumulation and dilation on one side of the interface, and fluid depletion and contraction on the other. Such a time-varying mechanical dipole creates a seismic wave. Material property dependencies of these couplings will be discussed along with interesting potential applications of the couplings. Numerical modeling of these effects will be presented along with both qualitative and mathematical descriptions of the mechanisms.
DE: 7299 General or miscellaneous
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting