On two approaches to studying the aftershocks of a strong earthquake

TL;DR

This paper compares traditional and new approaches to studying earthquake aftershocks, focusing on the source of earthquakes rather than aftershock frequency, and introduces a more effective measurement-based methodology that led to new discoveries.

Contribution

It introduces a novel measurement-based approach focusing on earthquake sources, revealing new phenomena like bifurcation and the Omori epoch in aftershock analysis.

Findings

Discovery of the Omori epoch in aftershock data

Identification of bifurcation in earthquake sources

Validation of the new approach's effectiveness

Abstract

The paper is devoted to comparing two approaches to the study of aftershocks. The methodological foundations of the traditional approach were laid many years ago. A new approach has emerged relatively recently. The two approaches differ from each other in the object, purpose and method of research. The differences are as follows. With the new approach, attention is focused not on aftershocks, but on the source of the earthquake. The evolution of the source is studied experimentally, and not the degradation of the frequency of aftershocks. Instead of a speculative selection of empirical formulas, the source deactivation coefficient is measured, variations in the coefficient are observed, and only on the basis of measurements and observations are conclusions drawn about the dynamics of the source. Thus, the divergence between the two approaches is doctrinal. The new approach turned out to be effective. Through targeted analysis of aftershock data, the Omori epoch and the phenomenon of bifurcation of the earthquake source were discovered. The purpose of further research is indicated. Keywords: earthquake source, Omori law, Hirano-Utsu law, logistic law, deactivation coefficient, bifurcation, master equation, methodology.