We developed a methodology that generates free externally disturbed magnetic variations in ground magnetometers close to the Chilean convergent margin. Spectral analysis (~ mHz) and magnetic anomalies increased prior to large Chilean earthquakes (Maule 2010, M_w 8.8; Iquique 2014, M_w 8.2; Illapel 2015, M_w 8.3). These findings relate to microcracks within the lithosphere due to stress state changes. This physical evidence should be thought of as a last stage of the earthquake preparation process.

Over the past few years, a number of data have emerged on predicting large earthquakes using the magnetic field. These measurements are becoming strongly supported by rock electrification mechanisms experimentally and theoretically in seismo-electromagnetic theory. However, the processes that occur within the faults have yet to be elucidated. That is why this work theoretically links the friction changes of the faults with the lithospheric magnetic anomalies that surround the faults.

Several authors have shown evidence of electromagnetic measurements prior to earthquakes. However, these investigations lack a physical mechanism to support them. That is why we developed a theory that could explain many of these phenomena. Specifically, we demonstrate that the generation of microcracks in the lithosphere due to stress changes can explain and describe these electromagnetic phenomena.

The latest research suggests that there could be a relationship between geomagnetic field variations and seismic events in different parts of the planet. These variations have been found in both ground-level magnetometers and satellites studying the ionosphere. The magnetic variations are similar between the earthquakes in Chile (2010, 2014, 2015) and the one in Mexico 2017. Therefore, the use of magnetic variations at ground level or ionospheric could show seismic precursors.