Microseismicity and Intensity of Relaxation Processes in the Earth's Crust

摘要

While analyzing the relaxation processes in the earth's crust, the microseismic background should be considered a permanently present vibration impact, which can systematically influence processes of energy exchange, including seismotectonic and gas-and fluid-dynamic processes. In the most general form, the microseismic background consists of superposition of oscillations with a statistically small amplitude in the selected time interval (background), regular seismic signals of natural origin (remote earthquakes, noise of seas and oceans, baric variations, and so on), and tech-nogenic (transport and other noises), and finally, pulsing microoscillations (PO), which accompany local relaxation processes in the earth's crust and can be considered an analog of earthquakes. Relaxation processes are related to a partial release of stresses in the earth's crust. They are accompanied with microdeformations in the form of steplike constrained rotation or shear of structural blocks of different sizes. In this relation, it is interesting to compare the number of relaxation events in the medium and amplitude of microseismic background. We note that accompanying PO relaxations are represented by a wide spectrum of amplitudes and frequencies. In the case of earthquakes, the number of PO increases significantly, while their amplitude decreases. Relaxation processes, which are characterized by a small amount of released energy (hence, small amplitude of PO), are observed everywhere. The number of PO (N) with amplitude, for example, 2-3 times greater than the background amplitude A, can be considered a measure of intensity of relaxation processes in a specific region of the earth's crust.