  The concept of proper time, which is different from universal time, has been
introduced into the physics of earthquakes. The global activity of strong
earthquakes was chosen as the object of study. We consider the sequence of
earthquakes as a random process of the Poisson type. Comparatively weak
earthquakes are used as the underground clock, the ticking of which marks the
course of proper time. The Poisson distribution is compared with the
distributions for two sequences of strong earthquakes. One of the sequences is
ordered by calendar time, and the second by proper time. The result of the test
showed that the distribution of events ordered by proper time is closer to the
Poisson distribution than the distribution of events ordered by calendar time.
We explain this by non-stationarity, which is an immanent property of the
Earth's lithosphere.
