A new technique for determining the precursors of an upcoming strong seismic event causing a tsunami is considered, based on the occurrence of the effect of topological similarity of statistical functionals \(L\left(n\right)\) from magnetic field measurements. The measurements were carried out using data from spatially distant magnetic standard observatories in Japan (KNY, KAK and MMB) before the earthquake of magnitude 7.3 on 03/16/2022 at 14:37 UTC in the Pacific Ocean near the central part of the Japanese Islands. For stations KNY, KAK and MMB, the minimum of the dependencies \(L\left(n\right)\) for the X- and Y-components, and stations KNY and MMB for the Z-component of the magnetic field, correspond to the time interval of 62–69 hrs before the event. This phenomenon can be used as a ‘regular’ (i.e., repeated with high probability) harbinger of approaching earthquakes that cause tsunamis.
