On the Regional and Local Factors of Earth-currents at the Kakioka Magnetie Observatory

[摘要] Part I.Earth-Current and Earthquake.Eliminating the so-called universal factors of earth-currents with two independent E-W Components, 1.5km. and 0.1km. long respectively, we find the following results. Earthquakes, especially larger scale ones, are frequently occurred near the max. or mim. points of the special variation of the above eliminated curves which have usually no appreciable change except the anomalous electrode change. This variation begins to occur some hours before the earthquake. The earthquakes are classified in three types, I-, D-, and M-type according to the increasing, decreasing and both mixed variation of the eliminated potential difference, in which case potential is taken as positve when west high.The geographical distribution of the three types is shown in Fig. 1, showing some intimated relation to the topography, or gravitational anomaly near the island.The amplitude AmV/100m and period T in hours of the variation lasted before the earthquake occurrence will be approximately expressed by the following empirical formulae in which Δ_??_1, whereΔis the distance from the observatory to the epicentre and ε and a, etc, are some constants. Some possible considerations regarding to this variation are proposed.

[学科分类] 大气科学