RU2433430C2 - Method for determining possibility of occurrence of catastrophic phenomena - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: signals at the water-ground boundary are picked up using ocean-bottom seismographs with 0.003-20 Hz wideband seismic channels, having sensors for weak seismic signals and sensors for strong bottom movements. The picked up signals are transmitted over a hydroacoustic communication channel to drift buoys and then further over a satellite channel to reference points. When processing signals, the decisive statistics used is the sum of the squares of amplitude values, which has a maximum value for the signal of the expected structure. Upon achieving the global maximum value equal to the average value between amplitude values characterised by the level of the state of natural geophysical fields, the possibility of the occurrence of catastrophic phenomena is determined.

EFFECT: broader functional capabilities, high reliability.

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Description

The invention relates to geophysics, and more specifically to methods for detecting the possibility of catastrophic phenomena occurring mainly at sea, and can be used to solve the following fundamental problems: studying the structure of the earth's crust in the waters of the oceans, studying the totality of geophysical fields in zones of tectonic faults directly at the bottom ocean, the study of the state of the marine environment in the bottom zone and its interaction with tectonic processes, geophysical monitoring are complex x hydraulic structures, rapid assessment of the seismic and hydrodynamic conditions of the regions and the forecast of possible seismic and environmental consequences, as well as with early warning of earthquakes and tsunamis.

It is known that due to the tectonic features of the Earth, over 80% of all earthquakes occur under the bottom of the seas and oceans [1, 2]. At the same time, the seismological network is located almost completely on the continents and some islands. Registration of remote strong sea quakes by ground seismographs leads to large errors in determining the magnitude and coordinates of hypocenters, weak sea quakes are practically not recorded. The strongest earthquakes with magnitude 8 or more, causing mainly catastrophic tsunami waves, are concentrated under the ocean floor near seismically active continental margins. In Russia, such areas are the coast of Kamchatka, the Kuril Islands and the island of Sakhalin. Currently, by means of a long-term seismological forecast, the locations of the expected strongest earthquakes in this region have been identified. This is Avacha Bay of Kamchatka and the Bussol Strait between the islands of Urup and Simushir of the South Kuril Islands. However, the time of occurrence of such earthquakes based on long-term forecasts is determined with an error of tens to hundreds of years.

Known methods are based on the use of deep-sea tsunami wave recorders installed along the protected coast [3, 4]. The height of the tsunami wave in the open ocean of 10 cm can increase many times in shallow water and pose a significant danger. Therefore, when setting to a depth of, for example, 3 km, registrars must have high sensitivity.

This sensitivity is provided by quartz pressure meters. To measure the thickness of the water layer, bottom sonar is used. The most developed tsunami monitoring and warning systems containing hundreds of ground-based seismographs and deep-sea recorders are available in the USA (DART, NOAA) and Japan (JAMSTEC). These systems have a high cost and a complex mathematical software for processing registered signals.

There is also a fundamental possibility of detecting tsunami waves using satellite observations [1, 2]. However, to ensure the required resolution in height and time of sequential scanning of the earth's surface no worse than 10-15 minutes, several dozen satellites must be launched into orbits.

In addition, to distinguish tsunami waves that are several centimeters high in the open ocean, complex mathematical processing is required to eliminate interference in the form of wind and tidal waves, wind surges.

A known method for detecting the possibility of the onset of catastrophic phenomena [5], including measuring the parameter of the geophysical field in a controlled area and judging by the data obtained on the possibility of the onset of catastrophic events, in which measurements are carried out continuously, detect fluctuations of the measured parameter and when detecting sinusoidal oscillations of increasing frequency with amplitude , statistically significantly different from the background for the controlled area, and the period from 100 to 1,000,000 s, judge about the availability the onset of catastrophic events.

The disadvantage of this method is that it has a low reliability of the forecast, since they measure only one parameter of the geophysical field. In addition, the sinusoidal oscillations of the measured parameter when superimposed on them by anthropogenic acoustic and hydrodynamic noises can be either periodic or aperiodic, which requires obtaining numerous arrays of the measured parameter to identify the amplitude that is statistically significantly different from the background, in order to achieve a positive technical result.

A known method of seismic micro-zoning [6], including the placement of the studied and reference points of observation in areas with different engineering and geological conditions, registration of seismic vibrations from earthquakes from potentially dangerous and other focal zones, determination of the dynamic parameters of seismic vibrations and their variations in each studied observation point relative to the reference in a given frequency range of studies, in which, in order to increase reliability by taking into account the lateral effect heterogeneous rock base and deeper horizons of the geological section additionally carry out three-component registration of seismic vibrations along an orthogonal profile network oriented to potentially dangerous focal zones, while the distance between the observation points does not exceed 1 / 3-1 / 4 of the wavelength of the most high-frequency seismic vibrations that form informative amplitude variations, and the distance between the profiles is 1 / 3-1 / 4 of the minimum spatial period of informative amplitude amplitudes iatsy highband seismic vibrations.

Performing a three-component registration of seismic oscillations according to an orthogonal, oriented to potentially dangerous focal zones network of profiles really increases the reliability of the classification of a possible earthquake. However, due to the fact that in the known method the determination of dynamic parameters is carried out by analyzing only the most high-frequency seismic vibrations, the achievement of the technical result, which consists in increasing the reliability of the forecast, is possible only with time-stable oscillatory processes and in the absence of interference caused by acoustic and hydrodynamic noise of natural and technogenic in nature. And if in land conditions with some assumptions the use of this method has a positive technical effect, then in marine conditions it is practically not applicable for predicting the possibility of a tsunami, since it is impossible to determine the nature of the bottom deformation at significant distances (large outbreak sizes), and a significant wave a tsunami occurs only with vertical or inclined movements. False alarms lead to large material losses.

In addition, the measurement base and the orientation of the measuring instruments with respect to the source play a significant role in improving the accuracy of measuring signals by which the precursors of catastrophic phenomena are established. So, for example, the spacing of meters at high and equatorial latitudes by more than 10 kilometers when measuring electrical and magnetic components leads to large (up to 50%) errors in impedance measurements.

Similar disadvantages are also known methods and devices designed for recording signals of seismic origin in marine conditions [7-23]. In the known methods, the significant value of the error is due to the fact that when processing the registered signals, the average signal propagation field is used. While the maximum deviations of the real field from the average differ precisely at the horizons of maximum gradients. In this case, the real field is very different from the ideal model. Under the influence of external factors using acoustic means for recording signals, a shadow zone is formed located in a strip from 5 to 16 kilometers from the source. Moreover, its length in different directions is not the same and can differ by 5 times or more, and with an increase in the distance between the receiver and the signal source, the errors increase. For marine conditions up to 15 kilometers, they are within 2 dB, then in the interval from 15 to 30 kilometers there is a sharp increase to 6 dB. Subsequently, in the interval from 30 to 60 kilometers, the error value monotonically increases to 7.5 dB.

The task of the invention is to expand the functionality of known methods with increasing the reliability of the forecast. The problem is solved due to the fact that in the method of detecting the possibility of the onset of catastrophic events, including micro-zoning with the placement of the investigated and reference observation points in areas with different engineering and geological conditions, measuring the parameters of the geophysical field in a controlled area and judging by the data obtained on the possibility of catastrophic events phenomena through bottom seismographs with broadband seismic channels of 0.003-20 Hz, containing sensors of weak seismic their signals and sensors of strong bottom movements, register signals at the water-ground boundary, transmit the registered signals via the hydroacoustic communication channel to drifting buoys located in the studied points, the recorded signals from which are transmitted through the satellite communication channel to reference points, when processing signals as For the decisive statistics, the sum of the squared amplitudes, having the maximum value for the signal of the expected structure, is used, while achieving a global maximum equal to the average th value of the amplitudes that characterize the levels of the state of natural geophysical fields, judge of the possibility of a catastrophic event.

New distinctive features consisting in registration by means of bottom seismographs with broadband seismic channels of 0.003-20 Hz, containing sensors of weak seismic signals and sensors of strong bottom movements, signals at the water-ground boundary, broadcasting of recorded signals through the hydroacoustic communication channel to drifting buoys located in the studied points, the recorded signals from which are transmitted via satellite communication channel to the reference points, used in the processing of signals as a decisive statistics of the sum of the squared amplitudes, which has the maximum value for the signal of the expected structure, and judgment when a global maximum is reached equal to the average value between the amplitudes characterizing the state levels of natural geophysical fields, about the possibility of a catastrophic phenomenon, allows you to get an operational assessment of the seismic state of the studied areas with more reliable prediction of possible seismic effects, as well as an earlier warning of impending earthquakes and tsunamis.

Known methods allow to achieve a technical result, which consists in increasing reliability, only in an isotropic field, since the nature of the decrease in the intensity of the sound signal with distance from the source in a horizontally inhomogeneous field (especially in the ocean) differs sharply from the same dependence in an isotropic field. Mesoscale inhomogeneities of the ocean (fronts, rings) dramatically rearrange the sound field, causing fluctuations in signal intensity up to 5 dB when predicting their range (D) up to 10 km. Therefore, for an effective forecast of hydroacoustic conditions in abnormal areas, a clear establishment of centers and boundaries, as well as determination of the parameters of disturbing formations, are necessary. Uncertainty in the calculation of the sound field by climatic data or the reference field is expressed in standard deviations of the real level from the reference at 4-9 dB, at D = 90 km, which corresponds to an error in the forecast of the expected range of hydroacoustic systems by 60-90%. The use of a single curve of the vertical distribution of the speed of sound for acoustic calculations is permissible only at short distances (up to 10 km), which is extremely rare in real conditions. By the magnitude and direction (sign) of the horizontal gradient along the signal propagation path, one can judge the degree of variability of the intensity of the sound field at the receiving horizon relative to a fixed source. For calculations of the acoustic field, the parameter is the sound velocity profile, which exactly matches the actual profile at the source location. However, when using regime information, the mean-square profile, as a rule, does not coincide with the actual one, which leads to additional random errors in the final result.

A set of new features from the prior art has not been identified, which allows us to conclude that the claimed technical solution meets the patentability criterion of "inventive step".

The method is implemented by a system, a block diagram of which is shown in the drawing.

The block diagram of the device for implementing the method includes: a bottom seismograph 1, consisting of sensors of weak seismic signals 2, sensors of strong bottom movements 3, a digital multi-channel storage device 4, a buffer memory 5, a control device 6, a sonar channel 7, a power source 8; drifting buoys 9 located on the sea surface and equipped with channels of hydroacoustic and satellite communications, strongholds 10, artificial Earth satellite 11. The essence of the method is as follows.

By means of sensors of weak seismic signals measuring three components (horizontal, vertical and inclined components) in the range of 0.003-0.1 Hz, and sensors of strong bottom movements in the range of 0.01-20 Hz, also measuring three components, signals are recorded at the interface sea water - sea soil.

As seismic sensors for the implementation of the claimed method, an acoustic seismic sensor is used, which is a three-component seismic-acoustic sensor, which is designed to convert the third derivative of soil vibrations into an electrical signal in the frequency range of 20-1000 Hz, the dynamic range of which is in the 1/3 octave band and center frequency 30 Hz is at least 60 dB, as well as an SM-5 type seismic receiver (cycle meter), including three seismic sensors with a recording frequency range with Amplitude signals 0.003-20 Hz, full dynamic range of at least 120 dB. A sensor with a range of up to 600 atm with a measurement error of 0.03% was used as a bottom pressure sensor.

The recorded signals are processed for each specific point in time to obtain a time dependence within the boundaries characterizing the state levels of natural geophysical fields.

The control device 6 analyzes the level of signals received from the sensors of weak seismic signals 2, and, in the case of increasing the threshold level, turns on the sensors of strong movements 3, and in the case of significant vertical or inclined velocities of the displacement of the bottom movement elements, generates a message packet that via the hydroacoustic communication channel 7 is transmitted to the drifting buoy 9. Since the control device 6 operates with inertia, to eliminate the loss of the first introductory strong bottom movements, the signals from the outputs of the sensors are weak with latter is present continuously recorded in the buffer memory 5, which are then used to determine the motion of the bottom element and recorded in the digital multi-channel information storage 4. In this case, the threshold level is determined by averaging over a long time period seismic noise coming from the outputs of weak seismic sensor 2 signals.

The signals received by the receiving antenna of the hydroacoustic communication channel of the drifting buoy 9 are formed into information packets for transmission to reference points 10 via artificial Earth satellites 11. The data conversion methods described in the source are analogs of the data conversion algorithm: Ilyin A.A., Marinich A.N. et al. Digital terminals of satellite communication systems. - SPb .: Deau, 2005, p.77-78, 89. As a satellite communication antenna on the drifting buoy 9 installed linear antenna polarization in the form of an asymmetric half-wave pin vibrator, providing the best energy characteristics in the region of small elevation angles of satellite devices.

The hydro-acoustic communication channel provides a range of up to 8000 m with a frequency range of signal transmitters commands 7-10 kHz.

When processing signals, the sum of the squared amplitudes having the maximum value for the signal of the expected structure is used as the decisive statistic. Calculations are performed for each point in time to obtain a time dependence for each field. The presence of a maximum in it means the presence in the source of the expected structure of the excitation of a field. The global maximum corresponds to the arrival time of the cumulative received signal. Upon reaching a global maximum equal to the average value between the amplitudes characterizing the state levels of natural geophysical fields, one judges about the possibility of a catastrophic phenomenon. The proposed method can also be used in land conditions. Devices for implementing the method in a wide assortment are available on the market, which allows us to conclude that the claimed technical solution meets the patentability condition “industrial applicability”.

Information sources

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Claims (1)

A method for detecting the possibility of the onset of catastrophic events, including micro-zoning with the placement of the investigated and reference points of observation in areas with different engineering and geological conditions, measuring the parameters of the geophysical field in the controlled area and judging by the received data on the possibility of catastrophic events, characterized in that by means of bottom seismographs with broadband seismic channels of 0.003-20 Hz, containing weak seismic signal sensors and strong sensors x bottom movements, register signals at the water-ground boundary, transmit registered signals via a hydroacoustic communication channel to drifting buoys located in the studied points, the recorded signals from which are transmitted via satellite communication channel to reference points, when processing the signals, the sum is used as the decisive statistics squares of amplitudes, having a maximum value for the signal of the expected structure, while achieving a global maximum equal to the average value between amplitudes rows, characterized by levels of the state of natural geophysical fields, judge of the possibility of a catastrophic event.