抄録
Observations of magnetic variations were made by means of portable fluxgate type magnetometers at Akagane (cp = 39°10:6 N, λ =141°20:6 E), Ishibuchi (ψ = 39°06:7 N, A = 140°54:6 E), Yuzawa (ψ = 39°10:2 N, A = 140°29:8 E) and the Mizusawa Geodetic Observa-tory (ψ = 39°06:5 N, A = 141°12:4 E) for the purpose of studying the conductivity anomaly along the east-west line including the Observatory in the Tohoku district of Japan. Using the observed events having the duration time longer than 30 minutes, the ele-ments of Parkinson Vector at four stations are obtained as shown in Table, whose direc-tions are eastward and opposite from those obtained by using the data of geomagnetic micropulsations having the periods of 10-60 seconds. A brief discussion was made about the relation between the conductivity anomaly and the crust and upper mantle structure in the Tohoku district which has typical geo-physical characteristics among circum-pacific island arcs.
