Earth’s gravity ― the reason of earthquakes
DOI:
https://doi.org/10.24028/gzh.0203-3100.v41i6.2019.190079Keywords:
earthquake, seismic radiation, weight, momentum, energyAbstract
In the paper, an attempt has been made to describe seismic processes by means of classical mechanics. Dynamic parameters such as energy, impulse, and forces that determine the movement of masses are estimated.
An earthquake model is regarded with consideration of the Earth gravity field influence on distribution of masses composing the Earth crust. The Earth crust is considered as a complex of geological bodies which is ordered by the planets gravity field. Due to isostasy the difference in density of the equal matter volumes leads to formation of mountain structures specific for the surface. When a base of such structures collapses a rock block shifts down and acquires mechanical impulse. Authors assume that this acquired mechanical impulse determines the earthquake’s magnitude.
Impulse propagates in medium as a seismic wave. Front of the wave generates pressure effected on an environment that is not active yet. It determines macro-processes of the earthquake measured as earthquake intensity. Authors consider mass (weight) of a rocks block, magnitude (mechanical impulse acquired during an impact), seismic emission, which is a distribution of a momentum and a pressure of wave front (product of impulse by time), as parameters of a seismic process. To estimate dynamic parameters of earthquake processes, such as shifted mass, mechanical impulse, pressure of wave front, a nomogram is presented. Magnitude of a seismic event has dimension of a mechanical impulse, seismic intensity (earthquake intensity) has a dimension of pressure. Nomogram consists of several parts. The first one, allows analyzing the source of the emission. It shows the relation between emitted momentum, mass of a shifted body and energy. The next part of the nomogram represents momentum density per unit of area of the wavefront, which decreases in proportion to the square of a distance from the source. It characterizes the spherical propagation of seismic radiation in an isotropic medium. The third part of the nomogram helps to estimate the value of an average seismic pressure of the wavefront. The last part of the nomogram allows rating the empirical characteristics of a seismic event. A relation between a scale of seismic pressure and standardized scale of seismic intensity MSK-64 is established. As an example a Spitaka earthquake, December 7th, 1988, was analyzed.
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