SU834649A1 - Earthquake predicting method - Google Patents

Description

(54) METHOD FOR PREDICTING EARTHQUAKES

I

The invention relates to seismology, in particular, to observations of the deformations of the earth's crust, which are considered to be precursors to an increase in seismic activity, causing the occurrence of earthquakes.

A known method for predicting earthquakes, according to which the angles of inclination of horizons in the earth's crust are measured in the epicenter zone of the supposed earthquake, and by their change over time, a change is made in the sex of the deformations and, as a result, the upcoming earthquakes 1.

This method is characterized by insufficient predictive reliability.

A method for predicting earthquakes is also known, in which the deformations and inclinations of the earth's crust are measured and the probability of an earthquake 2 is judged by changes in these parameters.

Such a method is also characterized by an insufficiently high reliability, since these parameters are complexly dependent on the magnitude, depth of the center and time of the earthquake.

The purpose of the invention is to increase the reliability of earthquakes.

The goal is achieved by determining the directions of the axes of the main stresses in the earthquake prediction method, which includes the registration of changes in the deformation rate of the earth's crust, identify areas with extremely high values of these stresses, and if there are deformation speed anomalies, they are re-determined stress directions and changes from absolute values, and by the simultaneous presence of velocity anomalies, deformations and reorientation of stress directions, an increase in seismic activity is judged vnosti.

The method is based on recording the tectonic component of the total (gravitational and tectonic) stresses at relatively small depths reached by mine workings. The gravitational component is determined, as is known, by the weight of the overburden

Claims (1)

(taking into account the concentration due to heterogeneities and discontinuities in the array) and is a constant and universally active factor. The tectonic component is determined by the conditions of tectogenesis and varies in space from region to region and in time. In the areas of tectonic stress, the largest of the components of the total tensor has a subhorizontal direction, whereas when only gravitational stresses act, the greatest of the components of their tensor is subvertical / direction. Consequently, one of the ways to search for precursors of earthquakes is to establish a qualitative change in the total stress field - to establish the fact and the moment of reorientation of the stress tensor. In conjunction with the establishment of the fact and the moment of a sharp change in the strain rate of the array under study, the observed phenomena may be indicative of an increase in seismic activity. The method is carried out as follows. At the first stage, the parameters of a regional voltage are determined (orientation in space of the axes of the main stresses: maximum compression, intermediate voltage, minimum compression and the type of stress state). For this purpose, the mechanism of foci of the greatest possible number of earthquakes arising in the territory of the studied area for a number of years is determined, which allows to determine the orientation of the axes of the main stresses, which are relieved in each center at the time of land ing. The generalization of the data obtained allows us to reconstruct the stress field characteristic of the studied area, i.e., to obtain the aforementioned parameters of the regional field. In the second stage, measurements of the quantitative characteristics of the stresses are carried out, while simultaneously establishing the orientation of the stress tensor in the rock mass under study. The second stage is carried out in several stages. The internal communication between the stages is that the data of the previous stage provide the basis for the experiments of the next stage, while the accuracy and reliability of the information obtained increases. At the first stage, areas with extremely high tectonic stresses are identified. This is a search (diagnostic) stage. Estimates of the stress values of the mountain range are made. The relatively high likelihood (more than 0.5) of the manifest tectonic stresses and their high magnitude is evidenced by the belonging of the massif to the rocks of the crystalline basement and the manifestation of arrows or rocks in the roof of the horizontal workings. The second stage is an alternative analysis. 55 At this stage, by means of visual observations and (or) a well-known ultrasonic method for measuring the velocities of a longitudinal wave in an array, qualitative signs characterizing the structure of stress fields are revealed. At this stage, the nature of the stresses is determined (hydrostatic or non-hydrostatic), the orientation of the highest voltage is established (vertically or horizontally, if horizontal, then its approximate orientation in the plan), it is determined whether the stress field is uniform, i.e. Whether the characteristics of the field are maintained in different parts of the field. The third stage is instrumental measurements by the method of unloading (in the form of end measurements). The method is based on using the characteristics of elastic recovery of the shape of a rock element during its artificial separation from the massif. The determination of the stress state is performed by sensors glued to the end of the well, which is unloaded by pressing the annular gap. The calculation of the stress at the bottom of a well is performed according to the formulas of the theory of elasticity. Data on the magnitude and orientation of the main stresses are used in the next, third, method stage. The third stage is continuous measurements of crustal deformations. The measurements are carried out using quartz deformographs, which are installed along the directions of the main stresses continuously for a long time. The strain rate calculated on the basis of the measurements obtained during quiet periods varies smoothly and slightly. An abrupt change in speed indicates a violation of the stability in the stressed state of the mountain massif, which in turn is a sign of the preparation of a seismic event of greater or lesser force. Longer-term and significant changes in the rate of strain may be indicative of the preparation of a stronger earthquake. The observed fact of change in the strain rate must be confirmed by the reorientation of the mechanism of earthquake foci, which confirms the tectonic nature of the observed phenomenon. For this, the orientation of the stress tensor is re-determined. The application of the proposed method allows to approach the solution of the problem of forecasting earthquakes, the claims of the method for predicting earthquakes. including the registration of changes in the strain rate, the earth's crust, characterized in that, in order to improve the reliability of the prediction, the directions are determined 56 the axes of the main stresses, the parts of the direction of stresses are judged on ki with extremely high seismic elevation values, stress, measure the strain on the Sources of information, the specified axes, if any, taken into account during the examination anomalies of deformation rates of production-1- Press F. et al. Prediction of land-breeding of traces. M., “Peace, 1968, p. 41-54. voltages and their absolute changes2. Ulomov V.I. Earth crust dynamics values, and by, the presence of both ano- and forecast earthquakes. Tashkent, “Fan, Malia strain rates and reoriented 1974, p. 171-172 (prototype). 834649