Changes in the Direction of Magnetic Vector of Short-Period Geomagnetic Variations before the 1972 Sitka, Alaska, Earthquake

Abstract

Secular change of the transfer function for short-period geomagnetic variations at Sitka, Alaska, Magnetic Observatory is examined in association with the 1972 Sitka earthquake of magnitude 7.2, the epicentral distance of which was only 40 km from the observatory. The analysis is difficult due to the effect of fluctuations of the position of the auroral zone because of the high latitude of the observatory. It seems nevertheless likely that the transfer function underwent a marked change about 1 year prior to the main shock. © 1979, Society of Geomagnetism and Earth, Planetary and Space Sciences. All rights reserved.