Objetivo
Although it is obvious that, at least in the vicinity of the seismic source such as earthquake, chemical and nuclear explosion and vibrator, the material must behave in a non-linear way, the non-linear elastic properties of in situ rocks and their manifestation in seismic wave propagation, seismic and acoustic emission have attracted the attention of geophysicists only in recent times. Non-linear elastic phenomena have been the subject of vigorous research in the former Soviet Union during the last fifteen years. These investigations were focused on different kinds of phenomena such as non-linear interference of low-amplitude waves, propagating through passive media, and non-linear effects in seismoactive media. They are related to the extremely high sensitivity of acoustic and seismic emission to the state of stress and its changes as well as to seismic vibrations. Experimental field and laboratory investigations revealed the fact that non-linear interference is distinctly expressed even if the wave deformations are very small (10-7 and less). This result shows that non-linear elastic parameters may prove useful for seismic prospection and for studies of the Earth's deep interior as a source of independent information on the geological and physical properties.
A study of the in situ rocks reveals the strong response of the lithosphere in the form of seismoacoustic emission to natural and artificial processes such as: tectonic stress changes connected with strong earthquake processes; atmospheric pressure; speed of the Earth's rotation; earth tide stress variations; filling of artificial reservoirs; extraction of oil, gas, and minerals; shaking by explosions and earthquakes etc. These processes have a very complex physical nature and are the results of changes of rock properties under permanent and periodical changes of stress and interactions of physical and chemical processes in real media. One of the most interesting effects is the influence of weak artificial seismic vibrations on the oil output and recovery of old oil deposits.
The results obtained so far are encouraging but further systematic experimental and theoretical studies on a broad spatial and temporal scale are needed. Some of the available methods and tools have been developed in the participating geophysical institutions of Azerbaijan, Germany, Greece, Russia and Turkmenistan. The main expected fundamental result is new knowledge of the nature of non-linear elastic phenomena and Earth properties, structure and composition. The main expected practical results are the development of improved methods of seismic prospecting, earthquake prediction, hydrocarbon recovery and earthquake engineering.
Tema(s)
Convocatoria de propuestas
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14473 Potsdam
Alemania