The westward drift of the Earth’s oscillations after earthquakes

Resumo

The records of strong earthquakes (December 26, 2004, Sumatra; February 27, 2010, Chile; and March 11, 2011, Tohoku) from broadband IRIS seismic stations are analyzed. Several days after the events, oscillations of 128–130 minutes in period start and last for about a month. The period of oscillations exceeds that of the Earth’s spheroidal eigen oscillation with the lowest frequency (53.9 min) by a factor of about two. Oscillations are of opposite polarity at stations located near the epicenters and at the symmetric point in the other hemisphere of the Earth. They manifest as trains of fluctuations migrating westward at 2.5° per hour. The amplitude of oscillations is up to few μGal.