  Recently, the physics of aftershocks has been enriched by three new problems.
We will conditionally call them dynamic, inverse, and morphological problems.
Dynamic problem is to search for the cumulative effect of a round-the-world
seismic echo appearing after the main shock of earthquake. According to the
theory, a converging surface seismic wave excited by the main shock returns to
the epicenter about 3 hours after the main shock and stimulates the excitation
of a strong aftershock. The second problem is an adequate description of the
averaged evolution of the aftershock flow. We introduced a new concept about
the coefficient of deactivation of the earthquake source, and proposed an
equation that describes the evolution of aftershocks. Based on the equation of
evolution, we posed and solved the inverse problem of the physics of the
earthquake source. The third task is to model the spatio-temporal distribution
of aftershocks. Its solution refines our understanding of the structure of the
earthquake source.
