The geographical distribution of anomalous phase difference between the vertical and horizontal components of the geomagnetic Sq variation in Japan was studiesd . by using the result of the 1st order magnetic survey the Geographical Survey Institute and the records of the l Kakioka Magnetic Observatory.
Fig. 2 shows the distribution of the value of 8 defined as follows,
δ=(tZ.S-tII.S)-(tZ.K-tII.K),
where (tZ.S t, H.S) is the time difference between the maximum decrease of the vertical and horizontal components of the Sq at the 1st order magnetic station and (tZ.K-tH.K) is that obtained at Kakioka on the same day. As shown in Fig. 2, the values of δ are zero and minus in the south-east part of Hokkaido, east part of Tohoku, almost all of Kanto and Chubu, and the south coast of Kinki and Sikoku.
In these districts the electrical conductivity seems to be very low at a depth of severalhundred kilometers.
In order to find the world wide distribution of the phenomenon above mentioned, preliminary examination was done by using the data of mean Sq for summer and winter at observatories during the Second Polar Year.
The result of the study is shown in Fig . 5, which suggests that the distribution of the zero and minus values of (tZ-tX) denoted by Δ and X has some sort of relationship to that of the deep focus earthquakes and seems to support the hypothetical model proposed by T. RIKITAKE [4].
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