Magnetic Effects of the Double Earthquake of March 16, 2022 (Japan): Observation Results

The magnetic effects of strong earthquakes are considered using the example of a unique event: two underwater earthquakes of magnitude 6.0 and 7.3 that occurred on March 16, 2022 at close times (at 14:34 and 14:36 UTC, respectively) with a distance between sources of ~11 km. With the use of data from the Mikhnevo geophysical observatory of the IDG RAS (MHV) and a number of magnetic observatories of the INTERMAGNET international network, it is shown that in the absence of global geomagnetic disturbances, earthquakes were accompanied by characteristic variations of the Earth’s magnetic field recorded as a train of alternating geomagnetic field oscillations with an amplitude of ~2–8 nT and a period of ~30 min almost simultaneously at ~15:30 UTC by all magnetic observatories located at distances from 210 to ~13 000 km, as well as by variations in the periods of passage of the seismic and infrasonic signal in the MHV.