Self-Potential Variations Associated with Quarry Blasts

Abstract

We observed self-potential variations associated with quarry blasts. The amplitude of the observed self-potential across a pair of electrodes 20 to 50m apart is about 5-20mV in the distance range of 5-100m from the blast point. The variation of the self-potential began before the elastic wave arrival to the electrodes, and seem to have begun almost simultaneously with the rock blast. Later parts of the self-potential signals are very similar to those of the transverse components of seismic signals and indicate that the electric potential variation is induced by seismic-wave propagation, probably due to the electro-kinetic phenomena proposed by MIZUTANI et al. (1976), and experimentally studied by PARKHOMENKO (1964).
The cause of the earliest part of the self-potential variation is unknown. Since the present quarry blast is for shale and the site is highly wet, it is very unlikely for the piezo-electric effect to have caused such a large variation of electric potential field. The self-potential variation might be related to the phenomena such as tribo-electricity or charge separation on newly-created surfrces.
If the occurrence of self-potential variation associated with the present quarry blasts is generally true for any type of rock failure, the measurement of self-potentials on ground may yield a new tool for exploring a physical mechanism of natural earthquakes, as well as for determining the origin time of the earthquakes. Further field measurement and laboratory experiments are required to reveal the nature of the self-potential variation associated with rock failure.