RU2770130C1 - Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in ice-covered water areas - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention relates to the field of seismology and can be used in national geophysical measurement observation systems for predicting earthquakes. Proposed is a drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in ice-covered water areas, equipped with a vertical string of hydrophones, including an instrumentation module consisting of a sealed cylindrical instrumentation module composed of a control unit, and a power source, a satellite communication and navigation system unit, a control unit, and power sources. The station therein additionally comprises a three-component geophone, a recorder, a digital GPS compass, a tiltmeter, a temperature sensor, and a voltmeter installed on the power source. The analysis unit is configured to detect ultra-low-frequency amplitude modulations of hydroacoustic signals - precursors of strong earthquakes, as well as with select pulse signals by amplitude, repetition frequency, duration, and rate of buildup of the front of seismic waves and T-waves of strong earthquakes. The three-component geophone is therein made with active feedbacks, the analysis unit is made in the form of a recorder operating in the continuous recording mode for detecting a seismic event issuing a message to the control computer about the predetermined threshold being exceeded or recording the results to a "solid-state" memory with a volume of up to 32 gigabytes at preset time intervals ("by the calendar"). The analysis unit also comprises four seismic recording channels with an instantaneous dynamic range greater than 136 dB, a highly stable quartz crystal oscillator with long-term instability of 10^-7 and is configured to be controlled via the built-in "Ethernet 10/100" interface and is made with a range of recorded frequencies of 0.1…240 Hz. Seismic information is converted to the CSS and MiniSEED formats.

EFFECT: increase in the reliability and accuracy of recording seismic signals in the seas of the Arctic basin.

7 cl

Description

The invention relates to the field of seismology and can be used in national systems for observing geophysical measurements for earthquake prediction.

Known methods of marine seismic exploration in marine areas with ice cover (Oceanology. Geophysics of the ocean, v. 1. Geophysics of the ocean floor. M., Nauka, 1979, p. 34 [1], US patent No. 4139074, 1979 [2], copyright certificate SU No. 18355938 A1, 10.04.1995 [3]), as a result of which seismographic equipment is placed in the marine environment by means of the technical devices of a surface vessel with its subsequent towing.

To do this, in water areas with ice cover, the water area is previously cleared of ice cover along the route of movement to form channels along which seismic transducers are towed using the method of reflected waves in studies in solid even drifting and non-drifting ice. In this case, the speed of the vessel is chosen based on the length of the seismic profile and the thickness of the ice. Processing of the registered signals is carried out to eliminate the noise of propeller rotation and the noise of ice destruction by the ship's hull. In this case, the noise of the seismic receiver is recorded at the initial observation point and after the final observation point in ice conditions during the time t ₁ .

Next, the spectral densities of the noise of the seismic receiver recorded before the initial and after the final observation points in the time window 0-t ₁ are calculated, the frequencies of the noise of ice destruction by the ship's hull are isolated, the spectral density of the noise of ice destruction at these frequencies is determined, and the spectral density of the traces with a seismic signal is calculated in the time window t ₂ -t _to , the weight coefficients at the frequencies of ice destruction by the ship's hull, taking into account which determine the seismic section of the geological environment. A significant disadvantage is the low reliability of the operation of outboard geophysical equipment in seismic surveys in solid, even drifting and non-drifting ice.

Drifting buoy sonar stations are also known for determining the precursors of strong earthquakes and tsunamis (patents JP No. 2003232865 A, 22.08.2003 [4], RU No. 61245 U1, 02.27.2007 [5], Krasny M.L., Malashenko A.E. Marine Research and Instrumentation on Sakhalin, Bulletin of the Far Eastern Branch of the Russian Academy of Sciences, 2004, No. 1, pp. 3-10 [6], U Ton Il et al. issue 1 [7], patent RU No. 2405176 C2, November 27, 2010 [8]).

For example, a drifting buoy hydroacoustic station [8] includes a hardware module, a satellite communication and navigation system unit, an analysis unit, a control unit, and power supplies. The station is equipped with a vertical string of hydrophones. The analysis unit is configured to detect ultra-low-frequency amplitude modulations of hydroacoustic signals - precursors of strong earthquakes; with the possibility of selecting impulse signals by amplitude, repetition frequency, duration and rate of rise of the front of seismic waves and T-waves of strong earthquakes - tsunami precursors. The use of such a station in ice-covered sea areas is problematic due to possible mechanical damage. In addition, seismic signals are received only on low-frequency hydrophones, which reduces the reliability of the forecast.

Also, the significant weight and size characteristics of the station, due to the placement of analysis units on it and, accordingly, significant energy consumption, can be attributed to the disadvantages. Drifting buoy hydroacoustic station [8] was chosen as a prototype.

The objective of the proposed technical solution is to increase the reliability and reliability of registration of seismic signals in the seas of the Arctic basin.

The problem is solved due to the fact that a drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover, equipped with a vertical garland of hydrophones, including a container in the form of a sealed cylindrical instrumental module, and consisting of a control unit, a power source, block of the satellite communication and navigation system, characterized in that the station additionally contains a three-component geophone, an analysis unit, a digital GPS compass-inclinometer. a temperature sensor and a voltmeter, which is installed on the power source, located in the container, moreover, the digital GPS compass-inclinometer is placed under the top cover of the container and is connected to the analysis unit by a cable, and the three-component geophone is rigidly attached to the bottom cover of the container, while the analysis unit is made in the form of a recorder with a recorded frequency range of 0.1 ... 240 Hz and contains four or eight seismic recording channels with an instantaneous dynamic range of more than 136 dB and operating in continuous recording mode with the ability to detect ultra-low-frequency amplitude modulations of hydroacoustic signals - precursors of strong earthquakes, as well as with the possibility of selecting impulse signals by amplitude, repetition frequency, duration and rate of rise of the front of seismic waves and T-waves of strong earthquakes-tsunami precursors.

At the same time, a three-component geophone is made with active feedback, the recorder issues messages to the control computer about exceeding a specified threshold or at predetermined time intervals with recording the results on a solid-state memory of up to 32 gigabytes, the recorder includes a highly stable crystal oscillator with a long-term instability of 10 "the recorder is controlled through the built-in interface "Ethernet 10/100", the built-in interface "Ethernet 10/100" allows you to connect the recorder via local networks, through cellular networks 3G.4G.GPRS routers to the global network "Internet", seismic information is converted in GSS, MiniSEED formats .

In order to monitor the ongoing propagation processes on the seabed, with multi-year sea ice cover in the high latitudes of the Arctic, caused by earthquakes, it is proposed to perform the necessary measurements using small aperture seismological installations installed on drifting ice floes.

The proposed drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis contains a vertical garland of hydrophones, a three-component geophone, a hardware module, a satellite communication and navigation system unit, an analysis unit, a control unit and power supplies, a digital GPS compass, a tiltmeter, a temperature sensor and voltmeter installed on the power source. The analysis unit is configured to detect ultra-low-frequency amplitude modulations of hydroacoustic signals - precursors of strong earthquakes, as well as to select pulse signals by amplitude, repetition frequency, duration and rate of rise of the front of seismic waves and T-waves of strong earthquakes - precursors of a tsunami.

In this case, the three-component geophone is made with active feedback.

The analysis unit is made in the form of a recorder with a recorded frequency range of 0.1 ... 240 Hz and operating in the continuous recording mode upon detection of a seismic event with the issuance of a message to the control computer about exceeding a predetermined threshold or at predetermined time intervals ("according to the calendar") with a record results on a "solid-state" memory up to 32 gigabytes and contains four or eight seismic registration channels with an instantaneous dynamic range of more than 136 dB, a highly stable crystal oscillator with a long-term instability of 10 ^-7 . The analysis unit is also configured to be controlled via the built-in "Ethernet 10/100" interface.

At the same time, the function of detecting ultra-low-frequency amplitude modulations of hydroacoustic signals - precursors of strong earthquakes, as well as the possibility of selecting pulse signals by amplitude, repetition frequency, duration and rate of rise of the front of seismic waves and T-waves of strong earthquakes - precursors of a tsunami .

An analogue of such a recorder is a digital recorder of seismic signals of the Delta 03M type, which is located vertically.

The recorder is designed for automatic recording of seismic signals from natural and artificial sources of seismic vibrations in the continuous monitoring mode with recording and displaying on the screen of the control computer seismic signals coming from the inputs of the recorder for regional seismic exploration. The control computer is installed at the regional dispatching station.

The recorder is designed for autonomous operation in the continuous recording mode, in the seismic event detection mode with the issuance of a message to the control computer about exceeding a predetermined threshold or at predetermined time intervals ("according to the calendar") with recording the results to a "solid-state" memory up to 32 gigabytes .

The recorder has four or eight seismic registration channels with an instantaneous dynamic range of more than 136 dB, a highly stable crystal oscillator with a long-term instability of 10 ^-7 . A mode of continuous adjustment of the reference oscillator using the built-in GPS receiver is provided. The recorder also has a built-in seismic receiver calibration mode.

The registrar is controlled via the built-in "Ethernet 10/100" interface, which allows it to be connected via local networks, via networks of a cellular communication system (3G, 4G, GPRS routers) to the global network "Internet".

The main technical characteristics of the recorder: the range of registered frequencies, Hz 0.1…240; per channel signal amplification (CS), dB 0, 12, 24, 36; integrated noise level, reduced to the input at KU=24 dB, not more than, µV in the band 0.1…7.5 Hz 0.05; in the band 0.1…15 Hz 0.07; in the band 0.1…30 Hz 0.09; in the band 0.1…60 Hz 0.12; in the band 0.1…120 Hz 0.15; in the band 0.1…240 Hz 0.18; coefficient of non-linear distortion, no more than, % 0.001; instantaneous dynamic range at KU=0 dB, not less than, dB:

in the band 0.1 ... 7.5 Hz 130;

in the band 0.1…15 Hz 127;

in the band 0.1…30 Hz 124;

in the band 0.1…60 Hz 121;

in the band 0.1…120 Hz 118;

in the band 0.1…240 Hz 115;

The software allows remote real-time control of the exact time clock, operating modes of recorders connected to the seismological network, as well as receiving current seismic information directly at the processing point. Seismic information is converted into CSS, MiniSEED formats.

The recorder provides the possibility of building stationary systems for operational seismological monitoring and forecasting without or with a minimum set of additional equipment.

The following cables are connected to the recorder via connectors:

- cable from seismic receiver SPV-3k;

- from the battery power cable 12 V DC;

- external GPS antenna cable;

- cable from digital compass/tiltmeter;

- Ethernet LAN cable

The 3-component geophone SPV-3k is rigidly attached to the bottom cover.

The SPV-3k velocimeter has small dimensions and is a capacitive seismometer with active feedback (Mishin A.V. et al., Compact seismic receiver SPV-3K, // Instruments and systems of exploration geophysics, No 1, 2013, pp. 35-38 ). The mechanical design of the device is made according to modern technologies and is mass-produced with minimal use of imported components. The design of the seismic receiver provides the ability to work with it in a wide range of climatic conditions with its high reliability and ease of operation, including by untrained personnel. It has a low level of intrinsic noise, as a result of which it has an extended area of recorded signals. Main characteristics:

- number of components 3 (one vertical, two horizontal);

- frequency range by level -3 dB, Hz - 0.5 ... 65;

- frequency response unevenness no more than 1 dB in the frequency range, Hz - 0.6 ... 45;

- dynamic range, not less, dB - 120;

- conversion factor V*s/m, 500;

- maximum signal amplitude at balanced outputs, V ±3.5;

- constant component at the output, not more than, mV - ±10;

- allowable deviation of SPV-3k from the vertical, degrees ± 15;

- supply voltage (options):

unipolar unstabilized, V 6 ... 25;

- power consumption, W 0.65;

- operating temperature range, degrees С - -30…+55;

A cable with 12 V power supply and 3 information channels is connected to a digital seismic signal recorder.

A digital compass/tiltmeter is placed under the top cover of the container and provides a record of the station's magnetic declination and tilt. The compass/tiltmeter is connected by a cable to the registrar. This data is transmitted to the registrar and is available for download via the network.

Structurally, the proposed device contains a container with equipment, a power source (battery), a mast with an antenna connection, a modem and a GPS antenna, a hydrophone. A cable with a hydrophone is lowered into the water through a metal pipe with a diameter of 80 mm. Cable length 10 m. Weighted hydrophone at the end. The 3-component geophone SPV-3k is rigidly attached to the bottom cover of the container.

The station components are housed in a stainless steel container with an outer diameter of 290 mm. The size of the container allows it to be installed inside the ice floe in a 300 mm hole, which is drilled with a standard mechanical drill. The ice temperature does not fall below -30 degrees. The closer the container is to the bottom of the ice floe, the higher the temperature. The water temperature is not lower than -4 degrees.

The cover of the container contains connectors for the following cables:

- 12 V supply

-LAN

- hydrophone

- GPS antenna cable.

The proposed device can be used as a string of hydrophones, and one hydrophone.

When equipping the station, as in the prototype, a vertical 8-element equidistant garland of hydrophones (the distance between hydrophones is 25 m) installed in an underwater sound channel (the total signal is recorded, i.e., a linear antenna is formed with a radiation pattern oriented along the horizon). The frequency range is 0.5-2000 Hz, although it can be considered as a garland antenna in the frequency range 30-2000 Hz.). A weight is used to align the string of hydrophones into a line.

The power supply is located in a plastic sealed container. The capacity is 180 a/h and is made of rechargeable batteries made of lithium-titanate, providing operation in the temperature range of -50, 60 degrees.

The subscriber station of the satellite communication system, using an antenna, transmits hydrophysical and service information to the data processing center (control station), and the GLONASS satellite navigation system (GPS) determines the location. With the help of a radio antenna, radio exchange is carried out between the station and the dispatching station. At the same time, the radio antenna plays the role of an active radar transponder. The communication antenna, radio modem and GPS antenna are mounted on the mast. The mast is made remote and is a metal pipe 2 m high, which is frozen into the ice and strengthened with guy wires. A GPS antenna is attached to the top of the mast. The cable to the antenna is fed inside the mast. A vertical sector antenna with a modem is attached below. The LAN cable from the equipment container is connected to the modem inside the mast. The 12V power cable is connected from the battery to the radio modem inside the mast.

The control unit is a microcontroller that controls all station devices according to a given program or by a command received over the air from the central computer of the dispatching station.

In the earthquake and tsunami forecasting system, it is supposed to use simultaneously at least 4 spatially separated and synchronously operating stations installed both on drifting ice fields and multi-year ice.

The possibility of using seismic sensors with their installation on drifting ice fields is shown in the work “Seismoacoustic evidence of volcanic activity on the ultra-slowly propagating Gakkel Ridge, Arctic Ocean”, Geophys. Res. Lett., 32, L18306, DOI: 10.1029/2005GL023767. In this case, seismological installations with a small aperture were used.

Unlike the prototype, the registration of seismological data is carried out not only on a low-frequency hydrophone, which is less susceptible to interference from cracking ice, but also on a 3-component geophone. In addition, post-processing of the hydrophone data (pure P-wave) and the vertical Z component of the geophone makes it possible to clean the data from noise.

Processing of the recorded seismological data is performed according to well-known conventional methods.

A prototype of the proposed station in the version with one hydrophone has passed full-scale tests and is recommended for industrial production.

Information sources

1. Oceanology. Geophysics of the ocean, vol. 1. Geophysics of the ocean floor. M., Nauka, 1979.

2. US patent No. 4139074, 1979.

3. Copyright certificate SU No. 18355938 A1, 04/10/1995.

4. JP patent No. 2003232865 A, 22.08.2003.

5. Patent RU No. 61245 U1, February 27, 2007.

6. Krasny M.L., Malashenko A.E. Marine research and instrumentation on Sakhalin. Bulletin of the Far Eastern Branch of the Russian Academy of Sciences, 2004, No. 1, p. 3-10.

7. Wu Ton Il et al. Methodical developments in forecasting strong earthquakes by hydroacoustic methods. Marine research and technology for studying the nature of the World Ocean, 2005, no. one.

8. Patent RU No. 2405176 C2, November 27, 2010.

Claims (7)

1. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover, equipped with a vertical string of hydrophones, including a container in the form of a sealed cylindrical hardware module, consisting of a control unit, a power source, a satellite communication and navigation system unit, characterized in that the station additionally contains a three-component geophone, an analysis unit, a digital GPS compass-inclinometer, a temperature sensor and a voltmeter, which is installed on a power source, located in a container, moreover, a digital GPS compass-inclinometer is placed under the top cover of the container and is connected by a cable with an analysis unit, and a three-component geophone is rigidly attached to the bottom cover of the container, while the analysis unit is made in the form of a recorder with a recorded frequency range of 0.1 ... 240 Hz and contains four or eight seismic registration channels with an instantaneous dynamic range of more than 136 dB and operating in the continuous recording mode with the ability to detect ultra-low-frequency amplitude modulations of hydroacoustic signals-harbingers of strong earthquakes, as well as with the possibility of selecting impulse signals by amplitude, repetition frequency, duration and rate of rise of the front of seismic waves and T-waves of strong earthquakes-harbingers of a tsunami. 2. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover according to claim 1, characterized in that the three-component geophone is made with active feedback. 3. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover according to claim 1, characterized in that the registrar issues messages to the control computer about exceeding a predetermined threshold or at predetermined time intervals with recording the results on solid-state memory with a volume up to 32 gigabytes. 4. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover according to claim 1, characterized in that the recorder includes a highly stable quartz oscillator with a long-term instability of 10 ^-7 . 5. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in ice-covered waters according to claim 1, characterized in that the recorder is controlled via the built-in "Ethernet 10/100" interface. 6. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover according to claim 1, characterized in that the built-in interface "Ethernet 10/100" allows you to connect the recorder via local networks, via cellular networks 3G, 4G, GPRS routers to the global network "Internet". 7. Drifting buoy hydroacoustic station for determining the precursors of strong earthquakes and tsunamis in water areas with ice cover according to claim 1, characterized in that seismic information is converted in GSS, MiniSEED formats.