  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.
