Long period geomagnetic fluctuations after the 1964 Alaskan earthquake

Abstract

After the 1960 Chilean earthquake, Winch, Bolt and Slaucitjs reported [1] that periodic magnetic variations were observed having the same frequencies as the two lowest frequency torsional modes of the earth's free oscillations. The suggestion was made that the earth's oscillations might have induced the magnetic variations. The Alaskan earthquake of 28 March 1964 also excited the earth's eigenvibrations. However, the only power spectrum of the magnetic field reported for the period after the Alaskan earthquake failed to show any significant peaks [2]. In this note, we present power spectra of the post-quake geomagnetic field that do show lines having frequencies of several of the gravest torsional eigenmodes of the earth.