RU133946U1 - BOTTOM LASER SEISMOGRAPH - Google Patents

Abstract

1. The bottom seismograph, consisting of two sealed chambers made with the possibility of opening and interconnected by a fiber, equipped with a flat base and optical benches, on one of which an optical system is installed, made according to the scheme of a non-equal Michelson interferometer, including a semiconductor laser, a collimator, a dividing plate , two quotation mirrors on piezoceramic cylinders, rotary mirrors and a photo detector, and on the other a corner reflector, while the seismograph contains a p recording is the coupled to the photodetector and disposed in one of the chambers, and the optical bench are rigidly attached with bases cameras equipped gruntozatsepami.2. A bottom seismograph according to claim 1, characterized in that the chambers are made in the form of vertical cylinders provided with covers. A bottom seismograph according to claim 1, characterized in that a laser with a wavelength of 532 nm is used as a semiconductor laser.

Description

The utility model relates to the field of geophysics and can be used to measure microdeformations of the earth's crust at the bottom of the seas and oceans and study the spatiotemporal structure of geophysical fields in the infrasound and sound ranges.

Known autonomous bottom station for seismic observations (p. RU 2438149 C2, IPC G01V 1/38) designed for seismological monitoring, studying the fields of microseisms and hydroacoustic noise, as well as measuring and recording in a wide frequency range of seismic phenomena from local and remote earthquakes at the bottom seas and oceans. In this station, seismic and seismic acoustic sensors are used to record seismic signals. Seismic sensors are cycle meters and have three components: two horizontal and one vertical, and are designed to convert the speed of soil vibrations into an electrical signal in the corresponding dynamic and frequency range. The technical characteristics of the sensors are as follows: the frequency range of the recorded signals from 0.03 to 40 Hz. A three-component seismic-acoustic sensor is designed to convert the third derivative of soil vibrations into an electrical signal in the corresponding dynamic and frequency ranges. The main technical characteristics of the sensor: the number of seismic channels 3, the frequency range of 20-1000 Hz, the dynamic range in the 1/3 octave band and the center frequency of 30 Hz.

Known fiber-optic bottom seismograph (p. CN 101799555 (A), IPC G01V 1/18; G01V 1/38) consisting of a spherical chamber, in which there is a central load with fiber-optic accelerometers attached to it. The load is held in the center of the main spherical chamber by means of elastic suspensions. The main camera is installed in a metal frame, which serves to transmit vibrations from the bottom to the seismograph. Signals from the seismograph are transmitted to the recording device using a fiber optic cable.

Closest to the claimed one is a broadband bottom seismograph (VZ CN No. 101672927 (A), IPC G01V 1/18; G01V 1/38) consisting of two sealed spherical cameras, interconnected by a platform that provides communication between both cameras with the bottom. In one of the cameras there is a battery compartment and an acoustic signal processing board, in another camera there is a pendulum-type seismograph and an information storage device on which data obtained from the seismograph are recorded. The horizontal position of the seismograph is provided by a gimbal located in the same sealed chamber as the seismograph. Switching between cameras is provided by electric cables. This seismograph can record seismic vibrations in the frequency range from 0.025 to 40 Hz of both natural and artificial origin. However, the need to ensure the horizontalness of the seismograph assembly greatly complicates its design; in addition, it should be noted that it is impossible to monitor the seismic situation in real time.

A common drawback of all of the above seismographs is: the limited frequency and dynamic range, which do not allow measurements of variations in the Earth’s crust micro displacements in the infrasonic range, starting from a frequency of 0 Hz (conditionally) and, accordingly, are not able to record slow processes that can be harbingers of dangerous geodynamic phenomena.

The objective of the claimed utility model is the development of a bottom seismograph for measuring the micro displacements of the earth's crust in the infrasonic range.

The technical result is the expansion of the frequency and dynamic range of measurements of micro displacements of the earth's crust in the infrasound range.

The problem is solved by a bottom seismograph, consisting of two sealed chambers made with the possibility of opening and interconnected by a light guide, equipped with a flat base and optical benches, one of which has an optical system made according to the scheme of the Michelson non-uniform interferometer. including a semiconductor laser, a collimator, a dividing plate.

two alignment mirrors on piezoceramic cylinders, rotary mirrors and a photodetector, and another angle reflector, while the seismograph contains a recording system connected to the photodetector and located in one of the cameras, and the optical benches are rigidly attached to the bases of the cameras equipped with lugs.

The proposed design of the bottom seismograph based on a laser-interference optical system allows you to measure the micro displacement of the earth's crust in the frequency range from 0 to 1000 Hz with an accuracy of 0.03 nm.

Figure 1 shows a General view of the bottom seismograph: a - top view, b - side view, where 1 and 2 - sealed cameras, 3 - light guide, 4 - camera bases, 5 - lugs, 6 - optical bench with an optical system, 7 - optical bench with a sensible reflector - 8.

Figure 2 - schematically shows an optical system mounted on bench 6, where 9 is a laser, 10 is a collimator, 11 are two alignment mirrors mounted on piezoceramic bases (not shown in the diagram), 12 is a dividing plate, 13 is a rotary mirror , 14 - photodetector.

The cameras and the light guide of the bottom seismograph can be made of either metal or any suitable polymeric material. The chambers can be made in the form of vertical cylinders, which are equipped with caps or cylinders are made with the possibility of disconnecting them from the base of the chambers. To the base of the chambers are grousers, the specific implementation of which and their number depends on the nature of the soil. The sealing of the chambers is achieved using, for example, gaskets located in special grooves between the housing and the cover, or between the housing and the base.

A seismograph works as follows.

The beam of a stabilized semiconductor laser (9), passing through the collimator (10) and alignment mirrors (11), enters a translucent dividing plate (12), which is divided into two beams. The first beam, passing through the swing and compensation mirrors (13) and the translucent dividing plate (12), fall on the photodetector (14). The second beam, passing through the light guide (3) and reflected from the corner reflector (8) located on the optical bench (7), and passing through the translucent dividing plate (12), enters the photodetector (14). An interference pattern is configured on the photodetector (14) based on both beams, a change in which is associated with a change in the distance between the optical bench (6) and the reflector (8). A change in the interference pattern is detected by a photodetector (14) and converted into an electrical signal by a registration system (not shown in Fig. 2) located in one of the sealed chambers. Further, the electrical signal is transmitted using a signal cable connected to the registration system to the coastal post, where real-time recording is made to the storage medium. The measurement accuracy is determined by the accuracy of the measurement of the fraction of the interference band.

A seismograph makes it possible to measure variations in the interference pattern with an accuracy of 10 ^-4 × λ / 2, where λ is the laser wavelength. A prototype of the bottom seismograph was made in which chambers in the form of vertical cylinders with a height of 400 mm and a diameter of 400 mm and a light guide in the form of a pipe with a diameter of 150 mm and a length of 1500 mm were made of polymer material. When using a green semiconductor laser (532 nm) in the bottom laser interference seismograph, the measurement accuracy is approximately 0.03 nm in the frequency range from 0 to 1000 Hz.

Claims (3)

1. The bottom seismograph, consisting of two sealed chambers made with the possibility of opening and interconnected by a fiber, equipped with a flat base and optical benches, on one of which an optical system is installed, made according to the scheme of a non-equal Michelson interferometer, including a semiconductor laser, a collimator, a dividing plate , two quotation mirrors on piezoceramic cylinders, rotary mirrors and a photo detector, and on the other a corner reflector, while the seismograph contains a p recording is the coupled to the photodetector and disposed in one of the chambers, and the optical bench are rigidly attached with bases cameras equipped with lugs. 2. The bottom seismograph according to claim 1, characterized in that the cameras are made in the form of vertical cylinders provided with covers. 3. The bottom seismograph according to claim 1, characterized in that a laser with a wavelength of 532 nm is used as a semiconductor laser.

Images