Monitoring changes of the Earth's electric resistivity for earthquake and crustal activity research

Abstract

Stationary magnetotellurics (MT) monitoring systems were installed at the Mizusawa Geodetic Observatory and Esashi Observatory of the Geographical Survey Institute (GSI). The MT system monitors the electric resistivity of the Earth continuously in order to detect resistivity changes related to earthquake occurrence and crustal activity. Though day-to-day changes of the resistivity show large errors because of noise, careful analysis has produced good results. Eliminating noise and apparent changes, 30 percent changes of the apparent resistivity were found at Esashi, suggesting changes in electric current flow in a rather wide region.