Electromagnetic responses from seismically excited targets B: non-piezoelectric phenomena

Abstract

Seismoelectric exploration records the electrical (or magnetic) response from a seismic input in order to resolve targets that may not be amenable to other geophysical methods. The latter targets include quartz veins, relatively pure sphalerite and kimberlite. Various mechanisms have been proposed to explain the conversion of seismic to electromagnetic energy. Of these, piezoelectricity is the most familiar, This paper concentrates on other, less familiar, phenomena. We examine these in the context of four field experiments carried out in various geological settings. These settings are the quartz-ankerite Paymaster vein, near Timmins, Ontario; a road fill at Haney, British Columbia; and at the Mobrun, Quebec, and Sullivan, British Columbia, sulphide mines. The first two illustrate essentially linear conversion processes in which the measured electric field contains frequencies comparable with those in the seismic input. The third and fourth illustrate highly nonlinear processes with high-frequency impulsive responses. Brief descriptions are given of the experimental techniques that were used, and representative results are presented. In all cases, the measurements give information about targets of interest, and therefore suggest that seismoelectric techniques deserve more attention than has been afforded them in the past.