Who Invented the Seismograph - When Was It Invented? Who and when invented the first seismograph to predict earthquakes How does a seismograph work.

head of laboratory seismometry of the Institute of Physics of the Earth RAS

The past century gave the world the discovery of B.B. Golitsyn of the galvanometric method of observing seismic phenomena. The subsequent progress of seismometry was associated with this discovery. The successors of the Golitsyn case were the Russian scientist D.P. Kirnos, Americans Wood-Andersen, Press Ewing. Russian school of seismometry under D.P. Kirnos was notable for the careful study of the equipment and methods of metrological support for seismic observations. Recordings of seismic events have become the property of seismology when solving not only kinematic, but also dynamic problems. A natural continuation of the development of seismometry was the use of electronic means for obtaining information from the test mass of seismometers, its use in oscillography and in digital methods for measuring, accumulating and processing seismic data. Seismometry has always enjoyed the fruits of scientific and technological progress of the twentieth century. In Russia in the 70-80s. electronic seismographs have been developed that cover the frequency range from ultra-low frequencies (formally from 0 Hz) to 1000 Hz.

Introduction

Earthquakes! For those who live in active seismic zones, this is not an empty phrase. People live in peace, forgetting about the previous disaster. But suddenly, most often at night, IT comes. At first, only tremors, even throwing out of bed, clinking dishes, falling furniture. Then the roar of collapsing ceilings, non-permanent walls, dust, darkness, groans. So it was in 1948 in Ashgabat. The country learned about it much later. Hot. An almost naked Employee of the Institute of Seismology in Ashgabat that night was preparing to speak at a republican conference on seismicity and was writing a report. Started around 2 o'clock. He managed to run out into the yard. On the street, in clouds of dust and dark southern night, nothing was visible. His wife, also a seismologist, managed to get into the doorway, which was immediately closed on both sides by collapsed ceilings. Her sister, who had been sleeping on the floor due to the heat, was covered by a wardrobe whose doors opened to provide a "shelter" for the body. But the legs were pinched by the top of the cabinet.

In Ashgabat, several tens of thousands of residents died due to night time and the lack of anti-seismic buildings (I heard estimates of up to 50,000 people dead. In any case, G.P. Gorshkov, head of the Department of Dynamic Geology, Moscow State University, said so. Ed.) Well survived a building for which the architect who designed it was convicted for overspending.

Now in the memory of mankind, there are dozens of historical and modern catastrophic earthquakes that claimed millions of human lives. Of the strongest earthquakes, one can list such as Lisbon 1755, Japanese 1891, Assam (India) 1897, San Francisco 1906, Messina (Sicily-Calibria) 1908, Chinese 1920 and 1976. (Already much later than Ashgabat in 1976 in China, an earthquake claimed 250,000 lives, and last year's Indian one also killed at least 20,000 Ed.), Japanese 1923, Chile 1960, Agadir (Morocco) 1960 gyu, Alaska, 1964 ., Spitak (Armenia) 1988 After the earthquake in Alaska, Benyeoff, an American specialist in the field of seismometry, obtained a record of the Earth's own vibrations as a ball that was hit. Before and especially after a strong earthquake, there is a series - hundreds and thousands - of weaker earthquakes (aftershocks). Observation of them with sensitive seismographs makes it possible to delineate the area of ​​the main shock and obtain a spatial description of the earthquake source.

There are two means of avoiding large losses from earthquakes: anti-seismic construction and early warning of a possible earthquake. But both methods remain ineffective. Anti-seismic construction is not always adequate for the vibrations caused by earthquakes. There are strange cases of unexplained destruction of reinforced concrete, as was the case in Kobe, Japan. The structure of concrete is disturbed to such an extent that the concrete crumbles into dust at the antinodes of standing waves. There are rotations of buildings, as was observed in Spitak, Leninakan, in Romania.

Earthquakes are accompanied by other phenomena. The glow of the atmosphere, the disruption of radio communications and the no less terrible phenomenon of a tsunami, the sea waves of which sometimes occur if the center (center) of an earthquake occurs in a deep-sea trench of the world ocean (not all earthquakes occurring on the slopes of a deep-sea trench are tsunamigenic, but the latter are detected using seismographs by characteristic signs of displacement in the focus). So it was in Lisbon, in Alaska, in Indonesia. They are especially dangerous because almost suddenly waves appear on the shore, on the islands. An example is the Hawaiian Islands. The wave from the Kamchatka earthquake in 1952 came unexpectedly after 22 hours. A tsunami wave is imperceptible in the open sea, but when it comes ashore, it acquires a steepness of the leading front, the speed of the wave decreases and water surge occurs, which leads to a wave growth sometimes up to 30 m, depending on the strength of the earthquake and the relief of the coast. Such a wave was completely washed away in the late autumn of 1952, the city of Severo-Kurilsk, which is located on the shore of the strait between about. Paramushir and about. Shumshu. The impact of the wave and its movement back were so strong that the tanks that were in the port were simply washed away and disappeared "in an unknown direction." An eyewitness said that he woke up from the vibrations of a strong earthquake and could not fall asleep quickly. Suddenly, he heard a strong low-frequency rumble from the port side. Looking out the window and not thinking for a second what he was in, he jumped out onto the snow and ran to the hill, having managed to overtake the advancing wave.

The above map shows the most seismically active Pacific tectonic belt. The dots indicate the epicenters of strong earthquakes only for the 20th century. The map gives an idea of ​​the active life of our planet, and its data says a lot about the possible causes of earthquakes in general. There are many hypotheses about the causes of tectonic manifestations on the face of the Earth, but there is still no reliable theory of global tectonics that unambiguously defines the theory of the phenomenon.

What are seismographs for?

First of all, to study the phenomenon itself, then it is necessary to determine in an instrumental way the strength of the earthquake, its place of occurrence and the frequency of occurrence of these phenomena in a given place and the predominant places of their occurrence. The elastic vibrations excited by an earthquake, like a beam of light from a searchlight, are capable of illuminating the details of the Earth's structure.

Four main types of waves are excited: longitudinal, having a maximum propagation speed and coming to the observer in the first place, then transverse oscillations and the slowest - surface waves with oscillations along an ellipse in the vertical plane (Rayleigh) and in the horizontal plane (Love) in the direction of propagation. The difference in the time of the first wave arrivals is used to determine the distance to the epicenter, the position of the hypocenter, and to determine the internal structure of the Earth and the location of the source of earthquakes. By recording seismic waves that passed through the Earth's core, it was possible to determine its structure. The outer core was in a liquid state. Only longitudinal waves propagate in a liquid. The solid inner core is detected using transverse waves, which are excited by longitudinal waves that hit the liquid-hardness interface. From the picture of the recorded oscillations and types of waves, from the times of the arrival of seismic waves by seismographs on the Earth's surface, it was possible to determine the dimensions of the constituent parts of the core, their densities.

Other problems are being solved to determine the energy and earthquakes (magnitudes on the Richter scale, zero magnitude corresponds to energy and 10(+5) Joules, the maximum observed magnitude corresponds to energy and 10(+20-+21) J), spectral composition for solving the problem of seismic resistance construction, for the detection and control of underground tests of nuclear weapons, seismic control and emergency shutdown at such hazardous facilities as nuclear power plants, railway transport and even elevators in high-rise buildings, control of hydraulic structures. The role of seismic instruments in the seismic exploration of minerals and, in particular, for the search for "reservoirs" with oil is invaluable. They were also used in the investigation of the causes of the death of Kursk, it was with the help of these devices that the time and power of the first and second explosions were established.

Mechanical seismic instruments

The principle of operation of seismic sensors - seismometers - forming a seismograph system, which includes such nodes - a seismometer, a converter of its mechanical signal into electrical voltage and a recorder - an information storage device, is based immediately on Newton's first and third laws - the property of masses to inertia and gravity. The main element of the device of any seismometer is the mass, which has a certain suspension to the base of the device. Ideally, the mass should not have any mechanical or electromagnetic connections with the body. Just hang in space! However, this is still unrealizable under the conditions of the Earth's attraction. There are vertical and horizontal seismometers. First, the mass has the ability to move only in a vertical plane and is usually hung out with a spring to counteract the force of gravity of the Earth. In horizontal seismometers, the mass has a degree of freedom only in the horizontal plane. The equilibrium position of the mass is maintained both by a much weaker suspension spring (usually flat plates) and, especially, by the Earth's gravitational restoring force, which is greatly weakened by the reaction of the almost vertical suspension axis and acts in the almost horizontal plane of mass movement.

The most ancient devices for recording earthquake acts were discovered and restored in China [Savarensky E.F., Kirnos D.P., 1955] . The device had no means of recording, but only helped to determine the strength of the earthquake and the direction to its epicenter. Such instruments are called seismoscopes. The ancient Chinese seismoscope dates back to 123 AD and is a work of art and engineering. Inside the artistically designed vessel was an astatic pendulum. The mass of such a pendulum is located above the elastic element, which supports the pendulum in a vertical position. In the vessel, along the azimuths, there are the mouths of dragons, in which metal balls are placed. During a strong earthquake, the pendulum hit the balls and they fell into small vessels in the form of frogs with open mouths. Naturally, the maximum impacts of the pendulum fell along the azimuth on the earthquake source. From the balls found in the frogs, it was possible to determine where the earthquake waves came from. Such instruments are called seismoscopes. They are widely used today, providing valuable information about large earthquakes on a massive scale over a large area. In California (USA) there are thousands of seismoscopes recording with astatic pendulums on spherical glass covered with soot. Usually, a complex picture of the movement of the tip of the pendulum on the glass is visible, in which oscillations of longitudinal waves can be distinguished, indicating the direction to the source. And the maximum amplitudes of the recording trajectories give an idea of ​​the strength of the earthquake. The period of oscillation of the pendulum and its damping are set in such a way as to model the behavior of typical buildings and, thus, to estimate the intensity of earthquakes. The magnitude of earthquakes is determined by the external characteristics of the impact of vibrations on humans, animals, trees, typical buildings, furniture, utensils, etc. There are different scoring scales. In the media, "Richter scale" is used. This definition is designed for a mass inhabitant and does not correspond to scientific terminology. It is correct to say - the magnitude of the earthquake on the Richter scale. It is determined by instrumental measurements with the help of seismographs and conditionally denotes the logarithm of the maximum recording rate, related to the earthquake source. This value conditionally shows the released energy of elastic vibrations in the earthquake source.

A similar seismoscope was made in 1848 by the Italian Cacciatore, in which the pendulum and balls were replaced by mercury. During ground vibrations, mercury was poured into vessels spaced evenly along azimuths. In Russia seismoscopes of S.V. Medvedev are used, in Armenia seismoscopes of AIS of A.G. Nazarov are developed, in which several pendulums with different frequencies are used. They make it possible to roughly obtain vibration spectra, i.e. dependence of the amplitude of the records on the vibration frequencies during an earthquake. This is valuable information for designers of anti-seismic buildings.

The first seismograph of scientific importance was built in 1879 in Japan by Ewing. The weight for the pendulum was a cast-iron ring weighing 25 kg, suspended on a steel wire. The total length of the pendulum was almost 7 meters. Due to the length, a moment of inertia of 1156 kg was obtainedּ m 2. The relative movements of the pendulum and the ground were recorded on smoked glass rotating around a vertical axis. A large moment of inertia contributed to reducing the effect of friction of the pendulum tip on the glass. In 1889, a Japanese seismologist published a description of a horizontal seismograph, which served as the prototype for a large number of seismographs. Similar seismographs were made in Germany in 1902-1915. When creating mechanical seismographs, the problem of increasing sensitivity could only be solved with the help of Archimedes' magnifying levers. The force of friction during the recording of oscillations was overcome due to the huge mass of the pendulum. So Wiechert's seismograph had a pendulum with a mass of 1000 kg. In this case, an increase of only 200 was achieved for the periods of recorded oscillations not exceeding the pendulum's own period of 12 sec. Wiechert's vertical seismograph, whose pendulum weight was 1300 kg, had the largest mass, suspended on powerful helical springs made of 8 mm steel wire. The sensitivity was 200 for periods of seismic waves no higher than 5 sec. Wiechert was a great inventor and designer of mechanical seismographs and built several different and ingenious instruments. The recording of the relative motion of the inertial mass of the pendulums and the ground was carried out on smoked paper, rotated by a continuous tape by a clock mechanism.

Seismographs with galvanometric registration

A revolution in the technique of seismometry was made by a brilliant scientist in the field of optics and mathematics, Prince B.B. Golitsyn. He invented a method of galvanometric recording of earthquakes. Russia is the founder of seismographs with galvanometric registration in the world. For the first time in the world, he developed the theory of a seismograph in 1902, created a seismograph and organized the first seismic stations at which new instruments were installed. Germany had experience in the production of seismographs and the first Golitsyn seismometers were manufactured there. However, the recording apparatus was designed and manufactured in the workshops of the Russian Academy of Sciences in St. Petersburg. And until now, this device has all the characteristic features of the first registrar. The drum, on which photographic paper, almost 1 m long and 28 cm wide, was fixed, was put into rotational motion with a displacement at each revolution by a distance chosen and changed according to the observation task along the axis of the drum. The separation of the seismometer and the means of recording the relative movements of the inertial mass of the device was so progressive and successful that such seismographs received worldwide recognition for many decades to come. B.B. Golitsyn singled out the following advantages of the new method of registration.

1. The possibility of a simple technique to get more at that time sensitivity .

2. Carrying out registration for distance from the location of the seismometers. Remoteness, dry room, accessibility to seismic records for their further processing gave a new quality to the process of seismic observations and the exclusion of undesirable effects on seismometers by the personnel of the seismic station.

3. Independence of recording quality from drift zero seismometers.

These main advantages determined the development and use of galvanometric registration throughout the world for many decades.

The weight of the pendulum no longer played such a role as in mechanical seismographs. There was only one phenomenon that had to be taken into account - the magnetoelectric reaction of the galvanometer frame, located in the air gap of a permanent magnet, to the seismometer pendulum. As a rule, this reaction reduced the damping of the pendulum, which led to the excitation of its extra own oscillations, which distorted the wave pattern of the recorded waves from earthquakes. Therefore, B.B. Golitsyn used a mass of pendulums of the order of 20 kg in order to neglect the back reaction of the galvanometer to the seismometer.

The catastrophic earthquake of 1948 in Ashgabat stimulated the financing of the expansion of the network of seismic observations in the USSR. To equip new and old seismic stations, Professor D.P. Kirnos, together with engineer V.N. Soloviev, developed galvanometric seismographs of the general type SGK and SVK together with a GK-VI galvanometer. The work was started within the walls of the Seismological Institute of the USSR Academy of Sciences and its instrumental workshops. Kirnos' devices were distinguished by their thorough scientific and technical study. The technique of calibration and operation has been brought to perfection, which ensured high accuracy (about 5%) of the amplitude and phase frequency response (AFC) when recording events. This allowed seismologists to set and solve not only kinematic, but also dynamic problems when interpreting records. In this way, the school of D.P. Kirnos favorably differed from the American school of similar instruments. D.P. Kirnos improved the theory of seismographs with galvanometric registration by introducing the coupling coefficient of a seismometer and a galvanometer, which made it possible to construct the amplitude frequency response of a seismograph to record ground displacement, first in the band of 0.08 - 5 Hz, and then in the band of 0.05 - 10 Hz using newly developed seismometers of the SKD type. In this case, we are talking about the introduction of broadband frequency response into seismometry.

Russian mechanical seismographs

After the catastrophe in Severo-Kurilsk, a Government Decree was issued on the establishment of a tsunami warning service in Kamchatka, Sakhalin and the Kuril Islands. The implementation of the Decree was entrusted to the Academy of Sciences, the USSR Hydrometeorological Service and the Ministry of Communications. In 1959, a commission was sent to this region to clarify the situation on the ground. Petropavlovsk Kamchatsky, Severo-Kurilsk, Yuzhno-Kurilsk, Sakhalin. Means of transportation - LI-2 aircraft (former Douglas), a steamer raised from the bottom of the sea and restored, boats. The first flight is scheduled for 6 am. The commission reached the airport "Khalatyrka" (Petropavlovsk-Kamchatsky) on time. But the plane took off earlier - the sky over Shumshu opened up. A couple of hours later, a cargo LI-2 was found and a safe landing took place on the base strip with underground airfields, built by the Japanese. Shumshu is the northernmost island in the Kuril chain. Only in the northwest from the waters of the Sea of ​​​​Okhotsk rises the beautiful cone of the Adelaide volcano. The island looks completely flat, like a thick pancake among sea waters. On the island, mostly border guards. The commission arrived at the southwestern pier. A naval boat was waiting there, which rushed at high speed to the port of Severo-Kurilsk. On the deck, in addition to the commission, there are several passengers. At the side, a sailor and a girl are talking enthusiastically. The boat at full speed flies into the water area of ​​the port. The helmsman on the manual telegraph gives a signal to the engine room: "Ding-ding", and another "Ding-ding" - no effect! Suddenly a sailor at the side flies head over heels down. Somewhat late - the boat cuts quite strongly into the wooden railings of the fishing schooner. Chips fly, people almost fall. The sailors silently, without any emotion, moored the boat. Such is the specificity of service in the Far East.

There was everything on the trip: light rain, the drops of which flew almost parallel to the ground, small and hard bamboo - the habitat of bears, and a huge "string bag" into which passengers were loaded (a woman with a child in the center) and lifted by a steam winch to the deck of the restored ship due to a large storm wave, and the GAZ-51 truck, in the open body of which the commission crossed Kunashir Island from the Pacific Ocean to the Okhotsk coast and which turned around many times in a huge puddle halfway - the front wheels in one glue, the rear wheels in another - until then until the rut was corrected with an ordinary shovel, and the surf line at the entrance to the spawning stream, marked by a continuous strip of red salmon caviar.

The Commission found that so far the only seismic instrument capable of fulfilling the task of a tsunami warning service can only be a mechanical seismograph with registration on sooty paper. The seismographs were developed in the seismometric laboratory of the Institute of Physics of the Earth, Academy of Sciences. A seismograph with a low magnification of 7 and a seismograph with a magnification of 42 were supplied to equip specially built tsunami stations. The smoked paper drums were driven by spring clock mechanisms. The weight of the mass of the seismograph with a magnification of 42 was collected from iron disks and amounted to 100 kg. This ended the era of mechanical seismographs.

A meeting of the Presidium of the Academy of Sciences dedicated to the implementation of the Government Decree was held. Chairman Academician Nesmeyanov with a large, imposing, tanned face, short Academician-Secretary Topchiev, members of the Presidium. The well-known seismologist E.F.Savarensky reported, demonstrating a full-length photo of a mechanical seismograph [Kirnos D.P., Rykov A.V., 1961] . Academician Artsimovich took part in the discussion: "The tsunami problem is easily solved by transferring all objects on the coast to heights above 30 meters!" . Economically, this is impossible and the issue of units of the Pacific Fleet is not being resolved.

In the second half of the 20th century, the era of electronic seismographs began. Parametric transducers are placed on the pendulums of seismometers in electronic seismographs. They got their name from the term - parameter. The capacitance of an air capacitor, the inductive reactance of a high-frequency transformer, the resistance of a photoresistor, the conductivity of a photodiode under an LED beam, a Hall sensor, and everything that came to hand to the inventors of an electronic seismograph can serve as a variable parameter. Among the selection criteria, the main ones turned out to be the simplicity of the device, linearity, low level of intrinsic noise, efficiency in power supply. The main advantages of electronic seismographs over seismographs with galvanometric registration are that a) the decrease in the frequency response towards low frequencies occurs, depending on the signal frequency f, not as f^3, but as f^2 - much slower, b) it is possible to use the electrical output of a seismograph in modern recorders, and, most importantly, in the use of digital technology for measuring, accumulating and processing information, c) the ability to influence all seismometer parameters using the well-known automatic feedback control (OS ) [Rykov A.V., 1963] . However, point c) has its own specific application in seismometry. With the help of the OS, the frequency response, sensitivity, accuracy and stability of the seismometer are formed. A method has been discovered to increase the own period of oscillation of the pendulum with the help of a negative feedback, which is unknown either in automatic regulation or in seismometry existing in the world [Rykov A.V.,].

In Russia, the phenomenon of a smooth transition of the inertial sensitivity of a vertical and horizontal seismometer into its gravitational sensitivity as the signal frequency decreases [Rykov AV, 1979] is clearly formulated. At a high signal frequency, the inertial behavior of the pendulum predominates; at a very low frequency, the inertial effect is reduced so much that the gravitational signal becomes dominant. What does it mean? For example, during vertical oscillations of the ground, both inertial forces arise, forcing the pendulum to maintain its position in space, and a change in gravitational forces due to a change in the distance of the device from the center of the Earth. As the distance between the mass and the center of the Earth increases, the force of gravity decreases and the mass receives an additional force that lifts the pendulum up. And, conversely, when lowering the device - the mass receives an additional force, lowering it down.

For high frequencies of ground vibrations, the inertial effect is many times greater than the gravitational one. At low frequencies, the opposite is true - accelerations are extremely small and the inertial effect is practically very small, and the effect of a change in gravity for the seismometer pendulum will be many times greater. For a horizontal seismometer, these phenomena will manifest themselves when the swing axis of the pendulum deviates from the plumb line, which is determined by the same gravitational force. For clarity, the amplitude frequency response of the vertical seismometer is shown in Fig.1. It is clearly shown how, with decreasing signal frequency, the sensitivity of the seismometer changes from inertial to gravitational. Without taking this transition into account, it is impossible to explain the fact that gravimeters and seismometers are capable of recording lunisolar tides. According to tradition, it would be necessary to extend the "velocity" line to such a low sensitivity that tides with periods of up to 25 hours and an amplitude of 0.3 m in Moscow could not would be discovered. An example of recording tide and tilt in a tidal wave is shown in Fig.2. Here Z is a record of the displacement of the Earth's surface in Moscow for 45 hours, H is a record of the tilt in a tidal wave. It is clearly seen that the maximum slope does not fall on the tide hump, but on the slope of the tidal wave.

Thus, the characteristic features of modern electronic seismographs are a broadband frequency response from 0 to 10 Hz of oscillations of the Earth's surface and a digital method for measuring these oscillations. The fact that Bennioff in 1964 observed the natural vibrations of the Earth after a strong earthquake using strainmeters (strainmeters) is now available to an ordinary electronic seismograph (The largest recorded earthquake in the United Stateswas a magnitude 9.2 that struck Prince William Sound, Alaska on Good Friday, March 28, 1964 The consequences of that earthquake are still clearly visible, including in the vast areas of the extinct forest, since part of the land was lowered over a distance of 500 km, in some cases up to 16 m, and in many places sea water went into the groundwater, the forest died. Note Ed.).

Figure 3 shows the radial (vertical) oscillation of the Earth on the fundamental tone in 3580 sec. after the earthquake.

Fig.3. Vertical Z and horizontal H components of the vibration record after the earthquake in Iran, March 14, 1998, M = 6.9. It can be seen that radial vibrations prevail over torsional vibrations having a horizontal orientation.

Let's show in figure 4 what a three-component record of a strong earthquake looks like after converting a digital file into a visual one.

Fig.4. A sample of digital recording of an earthquake in India, M=7.9, 01/26/2001, received at a permanent broadband station KSESH-R.

The first arrivals of two longitudinal waves are clearly visible up to 25 minutes, then on horizontal seismographs a transverse wave enters at about 28 minutes and a Love wave at 33 minutes. On the middle vertical component, there is no Love wave (it is horizontal), and in time, the Rayleigh wave begins (38 minutes), which is visible on both horizontal and vertical traces.

In photo No. 3 .4 you can see a modern electronic vertical seismometer, which shows examples of tide records, natural oscillations of the Earth and records of a strong earthquake. The main structural elements of the vertical pendulum are clearly visible: two disks of mass with a total weight of 2 kg, two cylindrical springs to compensate for the Earth's gravity and hold the mass of the pendulum in a horizontal position. Between the masses on the base of the device there is a cylindrical magnet, in the air gap of which a coil of wire enters. The coil is included in the design of the pendulum. In the middle "looks out" the electronic board of the capacitive converter. The air condenser is located behind the magnet and is small in size. The area of ​​the capacitor is only 2 cm (+2). A magnet with a coil is used to force the pendulum with the help of the feedback on the displacement, speed and integral of the displacement. OS provide frequency response shown in figure 1, the stability of the seismometer over time and high accuracy of measuring ground vibrations of the order of a hundredth of a percent.

Photo No. 34. Vertical seismometer of the KSESH-R installation with the case removed.

In international practice, Wieland-Strekaizen seismographs have gained recognition and wide distribution. These instruments are adopted as the basis for the World Network of Digital Seismic Observations (IRIS) . The frequency response of the IRIS seismometers is similar to the frequency response shown in Fig.1. The difference is that for frequencies less than 0.0001 Hz, the Wieland seismometers are more "clamped" by the integrated feedback, which led to greater temporal stability, but reduced sensitivity at ultra-low frequencies compared to KSESh seismographs by about 3 times.

Electronic seismometers are capable of discovering exotic wonders that may yet be contested. Professor E. M. Linkov at the University of Peterhof, using a magnetron vertical seismograph, interpreted oscillations with periods of 5 - 20 days as "float" oscillations of the Earth in orbit around the Sun. The distance between the Earth and the Sun remains traditional, and the Earth oscillates somewhat as if on a leash on the surface of an ellipsoid with a double amplitude up to 400 microns. There was a connection between these fluctuations and solar activity [see additionally Ref. 22].

Thus, seismographs have been actively improved over the 20th century. The beginning of the revolutionary beginning of this process was laid by Prince Boris Borisovich Golitsyn, a Russian scientist. Next in line, we can expect new technologies in inertial and gravitational measurement methods. It is possible that it is electronic seismographs that will finally be able to detect gravitational waves in the Universe.

Literature

1. Golitzin B. Izv. Permanent Seismic Commission AN 2, c. 2, 1906.

2. Golitsyn B.B. Izv. Permanent Seismic Commission AN 3, c. 1, 1907.

3. Golitsyn B.B. Izv. Permanent Seismic Commission AN 4, c. 2, 1911.

4. Golitsyn B., Lectures on seismometry, ed. AN, St. Petersburg, 1912.

5. E.F.Savarensky, D.P.Kirnos, Elements of seismology and seismometry. Ed. Second, revised, State. Ed. Techn.-theor. Lit., M.1955

6. Equipment and methods of seismometric observations in the USSR. Publishing house "Science", M. 1974

7. D.P. Kirnos. Proceedings of Geophys. Institute of the Academy of Sciences of the USSR, No. 27 (154), 1955

8. D.P.Kirnos and A.V.Rykov. Special high-speed seismic equipment for tsunami warning. Bull. Council for Seismology, "Tsunami Problems", No. 9, 1961

9. A.V. Rykov. Influence of feedback on the parameters of the pendulum. Izv. USSR Academy of Sciences, ser. Geofiz., No. 7, 1963

10. A.V. Rykov. On the problem of observing the oscillations of the Earth. Equipment, methods and results of seismometric observations. M., "Science", Sat. "Seismic Instruments", no. 12, 1979

11. A.V. Rykov. Seismometer and Earth vibrations. Izv. Russian Academy of Sciences, ser. Physics of the Earth, M., "Science", 1992

12. Wieland E.., Streckeisen G. The leaf-spring seismometer - design and performance // Bull.Seismol..Soc. Amer., 1982. Vol. 72. P.2349-2367.

13. Wieland E., Stein J.M. A digital very-broad-band seismograph // Ann.Geophys. Ser. B. 1986. Vol. 4, No. 3. P. 227 - 232.

14. A.V. Rykov, I.P. Bashilov. Ultra-wideband digital set of seismometers. Sat. "Seismic Instruments", no. 27, M., Publishing House of the OIPH RAS, 1997

15. K. Krylov Strong earthquake in Seattle February 28, 2001 http://www.pereplet.ru/nauka/1977.html

16. K. Krylov Catastrophic earthquake in India http://www.pereplet.ru/cgi/nauka.cgi?id=1549#1549

17. http://earthquake.usgs.gov/ 21. http://neic.usgs.gov/neis/eqlists/10maps_world.html These are the strongest earthquakes in the world.

22. http://www.pereplet.ru/cgi/nauka.cgi?id=1580#1580 Earthquake harbingers in near-Earth space - A new article has appeared in Urania magazine (in Russian and English). The work of MEPhI employees is devoted to earthquake prediction based on satellite observations.

Seismograph- a device that registers ground vibrations during an earthquake. Nowadays, these are complex electronic devices. Modern seismographs had their predecessors. The first seismograph was invented in 132 in China, and real seismographs appeared in the 1890s. The modern seismograph uses the property of inertia (the property to maintain the original state of rest or uniform motion). For the first time, instrumental observations appeared in China, where in 132 Chang-Khen invented a seismoscope, which was a skillfully made vessel. On the outer side of the vessel with a pendulum placed inside, the heads of dragons holding balls in their mouths were engraved in a circle. During the swing of the pendulum from the earthquake, one or more balls fell into the open mouths of the frogs, placed at the base of the vessels in such a way that the frogs could swallow them. A modern seismograph is a set of instruments that register ground vibrations during an earthquake and convert them into an electrical signal recorded on seismograms in analog and digital form. However, as before, the main sensitive element is a pendulum with a load.

Seismic waves pass inside the globe in places that are inaccessible to observation. Everything that they meet on the way changes them in one way or another. Therefore, the analysis of seismic waves helps to elucidate the internal structure of the Earth.

A seismograph can be used to estimate the energy of an earthquake. Relatively weak earthquakes release energy on the order of 10,000 kg/m, i.e. sufficient to lift a load weighing 10 tons to a height of 1 m. This energy level is taken as zero, an earthquake with 100 times more energy corresponds to 1, another 100 times more powerful corresponds to 2 units of the scale. Such a scale is called the Richter scale in honor of the famous American seismologist from California C. Richter. The number in such a scale is called magnitude and is denoted by M. In the scale itself, there is no upper limit, for this reason the Richter scale is called open. In reality, the Earth itself creates a practical upper limit. The strongest recorded earthquake had a magnitude of 8.9. Two such earthquakes have been recorded since the beginning of instrumental observations, both under the ocean. One happened in 1933 off the coast of Japan, the other in 1906 off the coast of Ecuador. Thus, the magnitude of an earthquake characterizes the amount of energy released by the source in all directions. This value does not depend on the depth of the source, nor on the distance to the observation point. The strength of an earthquake manifestation depends not only on the magnitude, but also on the depth of the source (the closer the source to the surface, the greater the strength of its manifestation), on the quality of soils (the more loose and unstable the soil, the greater the strength of manifestation). Of course, the quality of ground buildings also matters. The strength of the manifestation of an earthquake on the earth's surface is determined by the Mercalli scale in points. Points are marked with numbers from I to XII.

A device for recording vibrations of the earth's surface during earthquakes or explosions

Animation

Description

Seismographs (SF) are used to detect and record all types of seismic waves. The principle of operation of modern SF is based on the property of inertia. Any SF consists of a seismic receiver or seismometer and a recording (recording) device. The main part of the SF is an inertial body - a load suspended on a spring from a bracket, which is rigidly attached to the body (Fig. 1).

General view of the simplest seismograph for recording vertical oscillations

Rice. one

The body of the SF is fixed in solid rock and therefore sets in motion during an earthquake, and due to the property of inertia, the pendulum lags behind the movement of the soil. To obtain a record of seismic vibrations (seismograms), a recorder drum with a paper tape rotating at a constant speed, attached to the body of the SF, and a pen connected to the pendulum (see Fig. 1) are used. The displacement vector of the earth's surface is determined by the horizontal and vertical components; Accordingly, any system for seismic observations consists of horizontal (for recording displacements along the X, Y axes) and vertical (for recording displacements along the Z axis) seismometers.

For seismometers, pendulums are most often used, the swing center of which remains relatively calm or lags behind the movement of the oscillating earth's surface and the suspension axis associated with it. The degree of rest of the geophone swing center characterizes its operation and is determined by the ratio of the period T p of the soil oscillations to the period T of natural oscillations of the geophone pendulum. If T p ¤ T is small, then the center of the oscillations is practically immobile and the oscillations of the soil are reproduced without distortion. At T p ¤ T close to 1, distortions due to resonance are possible. At large values ​​of T p ¤ T , when soil movements are very slow, the properties of inertia do not appear, the swing center moves almost as a whole with the soil, and the seismic receiver stops recording soil vibrations. When registering oscillations in seismic exploration, the period of natural oscillations is several hundredths or tenths of a second. When registering vibrations from local earthquakes, the period can be ~ 1 sec, and for earthquakes remote at a thousand km, it should be on the order of 10 sec.

The principle of operation of the SF can be explained by the following equations. Let a body of mass M be suspended on a spring, the other end of which and the scale are fastened to the soil. When the soil moves up by the Z value along the Z axis (translational movement), the mass M lags behind due to inertia and shifts down the Z axis by the z value (relative movement), which generates a tensile force in the spring - cz (c is the spring stiffness). This force during movement must be balanced by the inertia force of the absolute movement:

M d 2 z¤ dt 2 = - cz,

where z = Z - z.

From this follows the equation:

d 2 z ¤ dt 2 + cz ¤ M = d 2 Z ¤ dt 2 ,

whose solution relates the true soil displacement Z to the observed z.

Timing

Initiation time (log to -3 to -1);

Lifetime (log tc from -1 to 3);

Degradation time (log td -3 to -1);

Optimal development time (log tk from -1 to 1).

Diagram:

Technical realizations of the effect

Horizontal seismometer type SKGD

A general view of a horizontal seismometer of the SKGD type is shown in fig. 2.

Scheme of the horizontal seismometer SKGD

Rice. 2

Designations:

2 - magnetic system;

3 - converter coil;

4 - suspension clamp;

5 - suspension spring.

The device consists of a pendulum 1 suspended on a clamp 4 to a stand fixed on the base of the device. The total weight of the pendulum is about 2 kg; the given length is about 50 cm. The leaf spring is under tension. In the frame fixed on the pendulum there is a flat induction coil 3 having three windings of insulated copper wire. One winding serves to register the movement of the pendulum, and a galvanometer circuit is connected to it. The second winding serves to adjust the attenuation of the seismometer, and a damping resistance is connected to it. In addition, there is a third winding for supplying a control pulse (the same for vertical seismometers). A permanent magnet 2 is fixed on the base of the device, in the air gap of which there are the middle parts of the windings. The magnetic system is equipped with a magnetic shunt, which consists of two soft iron plates, the movement of which causes a change in the strength of the magnetic field in the air gap of the magnet and, consequently, a change in the attenuation constant.

At the end of the pendulum, a flat arrow is fixed, under which there is a scale with millimeter divisions and a magnifying lens through which the scale and arrow are viewed. The position of the pointer can be read on a scale with an accuracy of 0.1 mm. The pendulum base is provided with three set screws. Two side ones serve to set the pendulum to the zero position. The front set screw is used to adjust the natural period of the pendulum. To protect the pendulum from various interferences, the device is placed in a protective metal case.

Applying an effect

SFs used to register ground vibrations during earthquakes or explosions are part of both permanent and mobile seismic stations. The existence of a global network of seismic stations makes it possible to determine with high accuracy the parameters of almost any earthquake occurring in different regions of the globe, as well as to study the internal structure of the Earth based on the characteristics of the propagation of seismic waves of various types. The main parameters of an earthquake primarily include: the coordinates of the epicenter, the depth of the focus, intensity, magnitude (energy characteristic). In particular, to calculate the coordinates of a seismic event, data on the arrival times of seismic waves at least three seismic stations located at a sufficient distance from each other are required.

Seismograph(from other Greek σεισμός - earthquake and other Greek γράφω - to write) or seismometer- a measuring device that is used in seismology to detect and record all types of seismic waves. An instrument for determining the strength and direction of an earthquake.

The first known attempt to make an earthquake predictor belongs to the Chinese philosopher and astronomer Zhang Heng.

ZhangHeng invented the device, which he named Houfeng " ” and which could record the vibrations of the earth's surface and the direction of their propagation.

Houfeng and became the world's first seismograph. The device consisted of a large bronze vessel with a diameter of 2 m, on the walls of which eight dragon heads were located. The jaws of the dragons opened, and each had a ball in its mouth.

Inside the vessel was a pendulum with rods attached to the heads. As a result of an underground shock, the pendulum began to move, acted on the heads, and the ball fell out of the dragon's mouth into the open mouth of one of the eight toads sitting at the base of the vessel. The device picked up tremors at a distance of 600 km from it.

1.2. Modern seismographs

First seismograph modern design was invented by a Russian scientist, prince B. Golitsyn, which used the conversion of mechanical vibration energy into electrical current.

The design is quite simple: the weight is suspended on a vertically or horizontally located spring, and a recorder pen is attached to the other end of the weight.

A rotating paper tape is used to record the vibrations of the load. The stronger the push, the further the feather deviates and the longer the spring oscillates.

The vertical weight allows you to record horizontally directed shocks, and vice versa, the horizontal recorder records shocks in the vertical plane.

As a rule, horizontal recording is carried out in two directions: north-south and west-east.

In seismology, depending on the tasks to be solved, various types of seismographs are used: mechanical, optical or electric with different types of amplification and signal processing methods. A mechanical seismograph includes a sensitive element (usually a pendulum and a damper) and a recorder.

The base of the seismograph is rigidly connected with the object under study, during the vibrations of which the movement of the load occurs relative to the base. The signal is recorded in analog form on recorders with mechanical recording.

1.3. Building a seismograph

Materials: Cardboard box; awl; ribbon; plasticine; pencil; felt-tip pen; twine or strong thread; a piece of thin cardboard.

The frame for the seismograph will serve as a cardboard box. It needs to be made of a fairly rigid material. Its open side will be the front of the device.

It is necessary to make a hole in the top cover of the future seismograph with an awl. If the stiffness for " frames» is not enough, it is necessary to glue the corners and edges of the box with adhesive tape, strengthening it, as shown in the photo.

Roll up a ball of plasticine and make a hole in it with a pencil. Push the felt-tip pen into the hole so that its tip protrudes slightly from the opposite side of the plasticine ball.

This is a seismograph pointer designed to draw lines of earth vibrations.

Pass the end of the thread through the hole in the top of the box. Place the box on the bottom side and tighten the thread so that the felt-tip pen is hanging freely.

Tie the top end of the thread to the pencil and rotate the pencil around the axis until you take out the slack in the thread. When the marker is hanging at the correct height (that is, just lightly touching the bottom of the box), secure the pencil in place with tape.

Slide a sheet of cardboard under the tip of the felt-tip pen to the bottom of the box. Adjust everything so that the tip of the felt-tip pen easily touches the cardboard and can leave lines.

The seismograph is ready to go. It uses the same operating principle as real equipment. A weighted suspension, or pendulum, will be more inertial in relation to shaking than a frame.

To test the device in practice, there is no need to wait for an earthquake. You just have to shake the frame. The gimbal will stay in place, but will begin to draw lines on the cardboard, just like a real one.

It's hard to imagine, but every year on our planet there are about a million earthquakes! Of course, these are mostly weak tremors. Earthquakes of destructive power occur much less frequently, on average, once every two weeks. Fortunately, most of them occur at the bottom of the oceans and do not bring any trouble to mankind, unless a tsunami occurs as a result of seismic displacements.

Everyone knows about the catastrophic consequences of earthquakes: tectonic activity awakens volcanoes, giant tidal waves wash entire cities into the ocean, faults and landslides destroy buildings, cause fires and floods and claim hundreds and thousands of human lives.

Therefore, people at all times sought to study earthquakes and prevent their consequences. So, Aristotle in the IV century. to i. e. believed that atmospheric vortices penetrate into the earth, in which there are many voids and cracks. The whirlwinds are intensified by fire and look for a way out, causing earthquakes and volcanic eruptions. Aristotle also observed the movements of the soil during earthquakes and tried to classify them, identifying six types of movements: up and down, from side to side, etc.

The first known attempt to make an earthquake predictor was by the Chinese philosopher and astronomer Zhang Heng. In China, these natural disasters have happened and happen extremely often, moreover, three of the four largest earthquakes in human history occurred in China. And in 132, Zhang Heng invented a device to which he gave the name Houfeng "earthquake weather vane" and which could record the vibrations of the earth's surface and the direction of their propagation. Houfeng became the world's first seismograph (from the Greek seismos "fluctuation" and grapho "I write") a device for detecting and recording seismic waves.

Aftermath of the 1906 San Francisco earthquake

Strictly speaking, the device was more like a seismoscope (from the Greek skopeo "I look"), because its readings were recorded not automatically, but by the observer's hand.

Houfeng was made of copper in the shape of a wine vessel with a diameter of 180 cm and thin walls. Outside the vessel were eight dragons. The dragon heads pointed in eight directions: east, south, west, north, northeast, southeast, northwest, and southwest. Each dragon held a copper ball in its mouth, and under its head sat an open-mouthed toad. It is assumed that a pendulum with rods was installed vertically inside the vessel, which were attached to the heads of dragons. When, as a result of an earthquake, the pendulum was set in motion, a rod connected to the head facing the shock opened the dragon's mouth, and the ball rolled out of it into the mouth of the corresponding toad. If two balls rolled out, one could assume the strength of the earthquake. If the device was at the epicenter, then all the balls rolled out. Instrument observers could immediately record the time and direction of the earthquake. The device was very sensitive: it caught even weak tremors, the epicenter of which was 600 km away from it. In 138, this seismograph accurately indicated an earthquake that occurred in the Lunxi region.

In Europe, earthquakes began to be seriously studied much later. In 1862, the book of the Irish engineer Robert Malet "The Great Neapolitan Earthquake of 1857: Basic Principles of Seismological Observations" was published. Malet made an expedition to Italy and made a map of the affected territory, dividing it into four zones. The zones introduced by Malet represent the first, rather primitive scale of shaking intensity.

But seismology as a science began to develop only with the widespread appearance and introduction into practice of instruments for recording soil vibrations, that is, with the advent of scientific seismometry.

In 1855, the Italian Luigi Palmieri invented a seismograph capable of recording distant earthquakes. He acted according to the following principle: during an earthquake, mercury spilled from a spherical volume into a special container, depending on the direction of vibrations. The container contact indicator stopped the clock, indicating the exact time, and started recording the earth's vibrations on the drum.

In 1875, another Italian scientist, Filippo Sechi, designed a seismograph that turned on the clock at the time of the first shock and recorded the first oscillation. The first seismic record that has come down to us was made using this device in 1887. After that, rapid progress began in the field of creating instruments for recording soil vibrations. In 1892, a group of English scientists working in Japan created the first fairly easy-to-use instrument, John Milne's seismograph. Already in 1900, a worldwide network of 40 seismic stations equipped with Milne instruments was functioning.

A seismograph consists of a pendulum of one design or another and a system for recording its oscillations. According to the method of recording pendulum oscillations, seismographs can be divided into devices with direct registration, transducers of mechanical vibrations and seismographs with feedback.

Direct recording seismographs use a mechanical or optical recording method. Initially, with a mechanical recording method, a pen was placed at the end of the pendulum, scratching a line on smoked paper, which was then covered with a fixing composition. But the pendulum of a seismograph with mechanical registration is strongly influenced by the friction of the pen on the paper. To reduce this influence, a very large mass of the pendulum is needed.

With the optical method of recording, a mirror was fixed on the axis of rotation, which was illuminated through the lens, and the reflected beam fell on photographic paper wound on a rotating drum.

The direct recording method is still used in seismically active zones, where soil movements are quite large. But to register weak earthquakes and at large distances from the sources, it is necessary to amplify the oscillations of the pendulum. This is carried out by various converters of mechanical displacements into electric current.

A diagram of the propagation of seismic waves from the source of an earthquake, or hypocenter (bottom) and epicenter (top).

The transformation of mechanical vibrations was first proposed by the Russian scientist Boris Borisovich Golitsyn in 1902. It was a galvanometric registration based on the electrodynamic method. An induction coil rigidly fastened to the pendulum was placed in the field of a permanent magnet. When the pendulum oscillated, the magnetic flux changed, an electromotive force arose in the coil, and the current was recorded by a mirror galvanometer. A beam of light was directed to the mirror of the galvanometer, and the reflected beam, as in the optical method, fell on photographic paper. Such seismographs won worldwide recognition for many decades to come.

Recently, the so-called parametric converters have become widespread. In these transducers, mechanical movement (movement of the mass of the pendulum) causes a change in some parameter of the electrical circuit (for example, electrical resistance, capacitance, inductance, luminous flux, etc.).

B. Golitsyn.

Seismological station adit. The equipment installed there captures even the slightest vibrations of the soil.

Mobile installation for geophysical and seismological studies.

A change in this parameter leads to a change in the current in the circuit, and in this case it is the displacement of the pendulum (and not its speed) that determines the magnitude of the electrical signal. Of the various parametric transducers in seismometry, two are mainly used photoelectric and capacitive. The most popular is the Benioff capacitive transducer. Among the selection criteria, the main ones turned out to be the simplicity of the device, linearity, low level of intrinsic noise, efficiency in power supply.

Seismographs are sensitive to vertical vibrations of the earth or to horizontal ones. To observe the movement of the soil in all directions, three seismographs are usually used: one with a vertical pendulum and two with horizontal ones oriented east and north. Vertical and horizontal pendulums differ in their design, so it turns out to be quite difficult to achieve complete identity of their frequency characteristics.

With the advent of computers and analog-to-digital converters, the functionality of seismic equipment has increased dramatically. It became possible to simultaneously record and analyze signals from several seismic sensors in real time, take into account the spectra of signals. This provided a fundamental leap in the information content of seismic measurements.

Seismographs are used primarily to study the earthquake phenomenon itself. With their help, it is possible to determine in an instrumental way the strength of an earthquake, the place of its occurrence, the frequency of occurrence in a given place, and the predominant places of occurrence of earthquakes.

Seismological station equipment in New Zealand.

Basic information about the internal structure of the Earth was also obtained from seismic data by interpreting the fields of seismic waves caused by earthquakes and powerful explosions and observed on the Earth's surface.

With the help of recording seismic waves, studies of the structure of the earth's crust are also being carried out. For example, studies in the 1950s show that the thickness of the crustal layers, as well as the wave speeds in them, vary from place to place. In Central Asia, the thickness of the crust reaches 50 km, and in Japan -15 km. A map of the thickness of the earth's crust has been created.

It can be expected that new technologies in inertial and gravitational measurement methods will soon appear. It is possible that it is the seismographs of the new generation that will be able to detect gravitational waves in the Universe.

Seismograph recording

Scientists around the world are developing projects to create satellite earthquake warning systems. One such project is the Interferometric-Synthetic Aperture Radar (InSAR). This radar, or rather radars, monitors the displacement of tectonic plates in a certain area, and thanks to the data they receive, even subtle displacements can be recorded. Scientists believe that due to this sensitivity, it is possible to more accurately determine areas of high voltage seismically hazardous zones.