  One hundred years ago, Fusakichi Omori died. Our paper is dedicated to his
memory. Omori made an outstanding contribution to the physics of earthquakes.
In 1894 he formulated the law of aftershock evolution. Omori's Law states that
after the main shock of an earthquake, the frequency of aftershocks decreases
hyperbolically with time. In this paper, we briefly describe one of the
directions of modern aftershock research. Keywords: earthquake, mainshock,
aftershock, evolution equation, deactivation coefficient, inverse problem,
trigger, proper time.
