Mirror triad of tectonic earthquakes

TL;DR

This paper introduces the concept of mirror triads in tectonic earthquakes, where foreshocks outnumber aftershocks around the main shock, challenging classical earthquake triad models and offering new insights into earthquake precursors.

Contribution

It identifies and characterizes the rare mirror triad phenomenon, expanding the understanding of earthquake sequences beyond classical models.

Findings

Mirror triads have more foreshocks than aftershocks within 24 hours of the main shock.

Often, mirror triads lack aftershocks entirely.

A schematic classification of tectonic triads is proposed.

Abstract

It is natural to call the trinity of foreshocks, main shock and aftershocks a classical triad. The magnitude of the main shock is always greater than the maximum magnitudes of foreshocks and aftershocks. In the classical triad, the number of foreshocks is less than the number of aftershocks. In many cases, foreshocks are completely absent even before very strong earthquakes. In this work, we found a rare but extremely interesting species of triad (we called it the mirror triad), in which the number of foreshocks is greater than the number of aftershocks at the interval of 24 h before and 24 h after the main shock. Quite often, aftershocks are absent in mirror triads at all. In this paper, we described the properties of mirror triads and made an attempt to understand their origin. A schematic classification of tectonic triads is proposed. Keywords: foreshock, main shock, aftershock, Gutenberg-Richter law, Bath law, Omori law, solitary earthquake.