Vertical seismoelectric profiling in a borehold penetrating glaciofluvial sediments

Abstract

Seismoelectric signals have been measured as a function of depth in a borehole penetrating glaciofluvial sands, silts, and glacial till using a broadband surface seismic source, and a downhole electrode array. Transient electric field pulses, with amplitudes of 1 to 4 μV/m accompanied the arrival of seismic P-waves at the electrodes but no simultaneous interfacial signals were observed above the noise floor of approximately 0.2 μV/m. The co-seismic effect was strongest in a sand and gravel layer where its amplitude is consistent with the predictions of a simplified theoretical model. Normalization of the amplitude logs by measurements of seismic particle velocity and electrical conductivity enhanced their sensitivity to changes in lithology and porosity. The results of this experiment suggest that co-seismic seismoelectric effects show potential as a porosity/permeability logging tool in the borehole environment.