Positive Electrification on Rock Surface Detected in Field Observations and Laboratory Experiments

Abstract

A large plate antenna, lying 1.2-m above the floor of an underground mine gallery in northeast Japan, detected electric signals when seismic waves arrived. One of the possible mechanisms is the positive electrification of the floor. Here, we inspected such electrification in a laboratory using an air-dried rock block quarried from the mine. The block under partial load showed the positive electrification on the surface of the unstressed volume. The assumption of positive holes is reasonable to explain the electrification. They are activated from the deformation of peroxy bonds, a populous lattice defect in rock-forming minerals. In case of the underground-detection, the seismic waves would activate p-holes near the floor.