Time variations in tidal responses of the medium before the Great Tohoku earthquake, Japan, according to the data from the source’s nearest seismic stations

Abstract

The time variations in tidal response of the medium before the Great Tohoku earthquake in Japan are analyzed based on the data from the F-net seismic network stations closest to the source of this event. According to the horizontal pendulum data from these stations, which record the northward tilts, the tidal tilt amplitudes demonstrated a linear growth associated with the changes in the elastic moduli during the accumulation of the tectonic stresses. The growth phase was followed by a sharp decrease in the amplitudes of the tilts due to the release of the stresses by the earthquake.