RU1817858C - Method for stress-deformation state of rock testing - Google Patents

Abstract

Usage: in geophysics. SUMMARY OF THE INVENTION: The background is recorded in a low-background chamber by a gamma spectrometric detector in the energy range up to 5 MeV. By the presence of statistically significant bursts in the time dependence, a change in the stress-strain state of the rocks is judged. 1 ill.

Description

The invention relates to earthquake prediction techniques and can be used in geophysical environmental monitoring.

The purpose of the invention is to increase sensitivity ...

The essence of the invention lies in the fact that the γ-ray sensor is located underground in a screen representing a low-background camera, the number of γ-rays is continuously measured in the energy range up to 5 MeV in different energy intervals, in our case, in the window 1.7-2 , 0 MeV, spectrometric information is recorded at least hourly, from the signal corresponding to the results of measurements per day, the values of the mathematically obtained harmonic of the daily course are subtracted, as well as the signals corresponding to the bursts of the flux intensity cosmically x rays and the remaining signals corresponding to statistically significant bursts used as a harbinger of earthquakes, a judgment is made about the place and time of the coming seismic event.

A low-background camera, located in an underground room with a depth sufficient to absorb the soft component of cosmic rays, consists of a massive multi-layer protection 1, γ-radiation detector 2 and electronic part 3 (power supply and spectrometer pulse counters).

The method is carried out as follows. A low-background chamber is assembled in the underground room, the depth of the laboratory (the degree of absorption of cosmic rays), the structure and materials of the chamber are selected so as to achieve the lowest possible background in the chamber, at which it is possible.

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the possibility of observing emission peaks carrying information about preparing the earthquake. From the position of minimum background and maximum sensitivity, a detector of} radiation is selected. The energy resolution of the detector is less important, since the radiation appears in a fairly wide energy range. The temporary instability of the spectrometric path is within 2–3% for the entire time of observation. The output sums the number of pulses in predetermined energy intervals corresponding to the radiation of radon and thoron products: 1.7-2.0 MeV, 2.5-3.4 MeV, total natural radioactivity (0.3-3, 4 MeV), cosmic rays (above 3.4 MeV). The interval of cosmic rays is a control, because bursts of CR intensity give rise to peaks unrelated to seismic. The sum of the pulses in the energy windows is periodically recorded (often enough) throughout the day. In our case, we used the interval 1.7–2.0 MeV, from which the bursts associated with the cosmic ray interval were subtracted, and the daily curve was constructed corresponding to the emanation variations in the laboratory atmosphere and in the surrounding hydraulic system and over the obtained daily curve, which is visible at harmonic analysis, peaks are recorded, which subsequently after a very definite time correspond to seismic events. Preliminary measurements show the dependence of the peak width and height on the strength and range of the earthquake. Moreover, the / S-counters of the radon daughter products located in the same working volume of the chamber, the γ-counters located outside the low-background chamber, the cosmic ray detectors, do not give similar peaks, from which it is concluded that these peaks are not associated with the fluid component, as well as by direct exposure to the penetrating component of cosmic rays detected by scintillation detectors. A possible mechanism is the appearance of radiation, for example neutron, in rocks during the preparation of earthquake and the birth of / quanta in the walls of massive protection. The source of neutrons can serve as nuclear reactions, occurring in rocks. Taking into account a certain dependence of the shape and magnitude of the peak on the range and strength of the earthquake canopy, determining the location of the earthquake canopy can be realized by a network of similar points (in workings, adits, wells, etc.).

The method was tested in an underground low-background laboratory in the Transcaucasian region (Tbilisi). We studied the energy window of 1.7–2 OMeV, the frequency of outputting the sum of the pulses — every hour, the test showed the continuation of the operating range up to 2.5 MeV. The unit worked in automatic mode for several years except for cases of planned measurement

it contains radioelements in rock samples. The time period was found between the peak preceding the earthquake and the seismic event itself. For earthquakes with K 5: 9 it is 9 ± 1 day. The sensitivity radius of the procedure was experimentally determined to be 200 km for narrow peaks. Anomalies such as a wide peak or generations (the presence of a number with a positive outlier negative) were associated

with especially strong earthquakes far up to 3000 km from the laboratory. Parallel analysis of the diurnal curve itself (associated with radon) increases the information content of the analysis of the state of stress-strain rocks.

Thus, the information content and reliability of the forecast increases due to the registration of a new method for monitoring the condition of rocks.

Testing the methodology in another - the North Caucasus region (Krasnodar Territory) in a similar low-background chamber at a depth of 40 m showed the presence of the same effect.

Claims (1)

SUMMARY OF THE INVENTION A method of controlling the stress-strain state of rocks, including recording the variations in time of the natural radioactive background a gamma-ray sensor mounted below the Earth’s surface, processing the registration results, according to the results of which a change in the stress-strain state of rocks is recorded, which is characterized by the fact that, in order to increase sensitivity, a sensor installed in a low-background camera continuously measures the spectrum γ radiation in the energy range up to 5 MeV, the number of γ quanta measured at least in the energy range 1.7–2.5 MeV is recorded at least hourly, and the time dependence of th information set by It is characterized by the presence of statistically significant bursts, the moment of occurrence of which is correlated with the moment of time preceding the change in the stress – strain state of the rocks. XXXX) 6 X VV 9 AX Ai-V9VgWWWV 99 X 0 y yy9999w999 5 999 $ 0 0 66 & 999 LXXXX 7777 7 ////// 77/7 /// / 777/7 //// Z // ////// 77 ///// 7 // 77 // Y ////////