On the foreshocks of strong earthquakes in the light of catastrophe theory

TL;DR

This paper applies catastrophe theory to analyze earthquake foreshocks, revealing patterns such as increased activity and decreasing frequency before mainshocks, suggesting foreshocks may trigger larger earthquakes.

Contribution

It introduces a catastrophe theory framework to interpret foreshock patterns and proposes that foreshocks can act as triggers for mainshocks based on observed precursory signals.

Findings

Foreshock activity sharply increases 3 hours before mainshock

Characteristic frequency of foreshocks decreases prior to mainshock

Strong foreshocks may trigger mainshocks through surface wave mechanisms

Abstract

It is useful to consider the earthquakes in terms of catastrophe theory. In the paper, we illustrate this statement by analysis foreshocks preceding the strong earthquakes. We focused on the so-called catastrophe flags, and on the triggers that cause the critical transitions. The analysis shows a sharp increase of foreshock activity 3 h before the mainshock. This result is reminiscent of the well-known activation of the ULF magnetic precursors of earthquakes. Furthermore, we found that the characteristic frequency of foreshock sequence decreases a few hours before the mainshock, which is consistent with a prediction of the catastrophe theory. Finally, the analysis testifies that the strong foreshocks seems may be triggers of mainshocks. The idea is that the surface waves propagating outwards from the foreshock return back to the vicinity of the epicenter after having made a complete revolution around the Earth and induce there the mainshock.