On the Anomalous Changes in the Earth-Potential and Their Causes

A study on the causes of anomalous changes in the earth-potential observed at Izu-Oshima

Abstract

   It has been so far impossible to prove that a given anomalous change in the earth-potential is due to a specific tectonic activity. However, we can correlate these two phenomena after we have eliminated all other possible causes such as meteorological or artificial disturbances.
   From our experiences of the observation of the earth-potential at the Magnetic Observatory, we can derive an empirical rule that rectangular changes in the earth-potential are caused by artificial disturbances. In our observation using telegraphic facilities at Mito, the author found that one of the several types (including rectangular ones) of artificial disturbances was caused by the leakage current from the electric trains on the Hitachi Electric Railway, which occurs in conjunction with certain meteorological phenomena.
   Uyeda et al. reported that the anomalous changes of the telluric potential observed at Izu-Oshima Island using telegraphic facilities are possibly precursors of earthquake swarms off the east coast of the Izu-Peninsula. The fact, however, that almost all their “signals” appear from 6 to 22 o'clock implies that those “signals” are of man-made origin. The author claims that those anomalous changes are not related with earthquakes but are caused by the precipitation and the telephone exchange repeaters at the observation station.