On the Magnetic Effects due to the Earthquake of March 16, 2022 in Japan

Abstract

—The magnetic effects of two similar underwater earthquakes with magnitudes of 6.0 and 7.3, which occurred on March 16, 2022, were considered in [Adushkin et al., 2023]. According to the data of INTERMAGNET magnetic observatories, these earthquakes were found to be accompanied (with a delay of ~55 min) by variations in the Earth’s magnetic field in the form of a train of quasi-periodic oscillations with an amplitude of ~2–8 nT and a period of ~30 min at distances of ~210 to ~3000 km from the epicenter. It was suggested in the aforementioned study that this magnetic effect is caused by a perturbation of the geodynamo as a result of the impact of seismic waves propagating deep into Earth. This interesting hypothesis requires a detailed discussion from different points of view. A more detailed analysis of the pattern of geomagnetic field perturbation at all latitudes, performed by us, leads to a conclusion that the found quasi-periodic perturbation is a mid-latitude response to auroral electrojet variations and is not related to the earthquake. According to our estimates, variations with a source at the core–mantle interface on a time scale less than 1 year cannot manifest themselves on the Earth’s surface at all.