ON THE STRESS WAVE IN THE EARTH'S BODY DUE TO DIFFERENTIAL ROTATION OF THE MANTLE AND CORE

Abstract

Seismic energy generated as a result of elastic deformation of tectonic plates or blocks of rocks is realized by unloading at deformations exceeding the ultimate strength of rocks. The currently generally accepted earthquake source models are essentially local and are not able to establish a connection between seismic activity and some geophysical phenomena on a planetary scale. One of the features of seismicity is the recurrence of strong earthquakes in one place after a certain time interval. The purpose of this work is to study the influence of differential rotation of the solid core and mantle on seismic processes. It has now been established that the rate of rotation of the solid core exceeds the rate of rotation of the mantle. In relative motion, the solid core makes one revolution presumably in 200–400 years. Earlier, based on this, an explanation was proposed for long-period variations in the length of the day. In this paper, on a simple mechanical model, it is shown that the differential rotation of the elastic mantle and the solid core of an ellipsoidal shape generates a stress wave in the Earth's body. The idea of a stress wave is qualitatively new in the physical description of a seismic process. To demonstrate this effect, a solution is given to the problem of deformation of an elastic spherical shell interacting with a dumbbell-shaped solid body rotating in its cavity. When solving the problem, the apparatus of spherical vectors was used. The stress distribution of the spherical layer inside the shell is constructed and the areas of greatest risk are identified. It is shown that taking into account the differential rotation leads to the migration of the zones of greatest risk with a period equal to half the period of a complete rotation of the dumbbell relative to the shell (100–200 years). The results of the work can be useful in studying the relationship between seismicity and planetary rotation regimes.