Enhancing the seismoelectric method via a virtual shot gather

The seismoelectric method is a new means of characterizing near surface aquifers and appears to be able to detect significant changes in permeability or pore fluid chemistry. Seismic energy is used to probe the properties of porous media via the electrokinetic effect by measuring the resulting electrical potential on the surface. Two types of signal are observed in practice: signals recorded simultaneously by many sensors due to the seismic wave encountering a change in sub-surface properties, and signals that are produced when the seismic wave is near a sensor. The first type of signal is the desired response, and the second type of signal is interference. As the second type of signal exhibits move-out with seismic velocities it can be removed with filtering in the F-K or t-p domain. In practice, the limited number of acquisition channels typically available and the strength of these unwanted signals compared to the desired signals limits the effectiveness of these methods. We propose and demonstrate a solution to this problem by combining shot records from 24 sensors at different shot positions to create a virtual 120 channel shot record that allows velocity or move-out dependent filters to perform more effectively. The application of this method of data collection and processing has allowed us to reliably detect seismoelectric signals originating from depths of up to 120 metres.