A new interpretation of magnetic field variation associated with the Matsushiro earthquakes.

Abstract

Local magnetic field variation observed during the Matsushiro earthquake swarm in central Honshu, Japan, is well correlated with the variation of spring-water outflow but not with that of the seismic activity. This indicates that the origin of the magnetic field variation is not the stress-induced piezomagnetic effect but may be the water-induced electrokinetic effect proposed by MIZUTANI et al. (1975). The electrokinetic effect combined with the observed amount of water discharge is found to give the correct magnitude and sign of the local magnetic field variation observed at the two stations in Matsushiro area.