New research shows that earthquakes create electromagnetic waves that are coming out at the fault lines, because it is the easiest pass for the field lines to the surface. Do you know if your unit could pick up the changes.
We have done a walk around with the EMF-390 at a known fault-line here on the north shore of Vancouver and we found that the unit alerted when we crossed each of the faults. As we walked down the trail it alerted again and there must be some hidden cracks where the magnetic field lines escape which the unit detected. If you have a 390 and you live near a fault give it a try! These faults are located in an are without cell coverage so it was not man made.
Alex Schwarz VE7DXW tells us that a paper was released by a team of scientists that included Phil Erickson (W1PJE). The paper explains the changes the Tonga eruption had on the Ionosphere. It not only created a huge plume of ash that had an effect, but also it was a seismic event that was picked up by the USGS as well as the RF-Seismograph. It lasted for days! https://www.essoar.org/doi/abs/10.1002/essoar.10510445.1