This is to summarize the writers' studies on the anomalous behavior of geomagnetic variations in Japan which were published in a series of papers in the Bulletin of the Earthquake Research Institute [1]. An anomalously large amplitude of the vertical component of geomagnetic variations is pointed out at Hermanus, S. A., and some observatories in Japan. The distribution especially in Japan is statistically examined. The anomaly is found in a limited area in the central part of Japan. The results of the analysis based on the potential theory show that the anomaly is caused by the magnetic field originating in the earth. The anomaly is well approximated by an apparent magnetic dipole situated under central Japan. But it still remains unknown why such a localized anomaly occurs on occasions of geomagnetic variation.
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Rikitake et al. (1953) studied this question.