Photon Antenna "Russia-Taiwan"
Since the creation of the first laser deformograph in the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences , tremendous work has been carried out to improve their optical schemes and increase sensitivity, resulting in the creation of various laser deformographs: two-coordinate , vertical and horizontal directions , spatially separated  and portable . The use of laser deformographs of various variants allowed to study the nature of different-scale geospheric processes, the source of generation of which was in the atmosphere, hydrosphere or lithosphere. To accurately "bind" the sources of these processes to one of the geospheres with the definition of the physics of their occurrence, laser-interference complexes consisting of laser deformographs, laser nanobarographs and laser measuring instruments for variations in the pressure of the hydrosphere have been created. Currently, at the Marine Experimental Station of the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences "Schultz Cape" the complex is used to study the origin and development of infrasonic and low-frequency sound waves and waves of the geosphere transition zone. At the first stage of studying the patterns of transformation of different wave and non-wave processes at the geosphere boundary, research is conducted with artificial sources (low-frequency hydroacoustic and seismoacoustic emitters, ships, explosions, etc.), for example , which allows us to study these regularities more thoroughly, since these experiments can be carried out repeatedly under various hydrological and meteorological conditions. At the second stage, the most important one, the research is conducted on natural objects with the solution of the above problems, but with the support of the results obtained with artificial sources, which made it possible to determine the source of many oscillations and waves with an exact "binding" to one of the geospheres. For example, if it was previously thought that quasi-harmonic oscillations with a period of the order of 10–15 min recorded on the shelf by hydrophysical receiving systems belong to short-period internal waves and are generated on the shelf by the sea tide, then processing of synchronous experimental data of the facilities of the above complex allowed as to conclude, that the source of these perturbations is in the atmosphere. But the origin of many recorded oscillations and waves cannot be determined only from the data of such a laser-interference complex. It is necessary to expand the geographical distribution of such complexes over the Earth. The main installations in these complexes are laser deformographs with their unique characteristics: the operating frequency range is from 0 (conditionally) to 1000 Hz, the accuracy of measuring the microdisplacements is 0.01 nm. To solve the problem of creating these complexes in different points of the Earth, the laser deformographs were initially located at three points, two of which are in Russia (Schultz Cape, Primorskii Krai, Transbaikalia (near Krasnokamensk)) and in the south of the Taiwan. The works were carried out within the framework of the FEB of the RAS’s "Far East" program of a joint research projects competition between the Far East Branch of the RAS and the Ministry of Science and Technology of Taiwan. Two laser deformographs, oriented approximately along the "north-south" and "west-east" lines, operated on the Shultz Cape, one laser deformograph operated each in Taiwan and in Transbaikalia. All the experimental data obtained were recorded in a single database of experimental data with subsequent processing and interpretation.
At the Marine Experimental Station of the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences in the location with the coordinates 42.58°N and 131.157°E, two laser classical-type deformographs with arm lengths of 52.5 and 17.5 m, the measuring arms of which are oriented with respect to the north-south line at an angle 18° (198°) and 110° (290°), respectively, are operated for a long time, see Fig. 1. Optical schemes of laser deformographs are created on the basis of a modified Michelson interferometer using frequency-stabilized helium-neon lasers. The first laser deformograph is located at a depth of 3–5 m from the surface of the earth in a hydrothermally insulated room at a height of 67 m above sea level, and the second laser deformograph is located at a distance of 70 m from the first one at a depth of 3–4 m from the surface of the earth in a similar hydrothermally insulated room. The angle between the measuring arms of laser deformographs is 92°. The interferometry methods used allow one to record the change in the lengths of the measuring arms of each laser deformograph with an accuracy of 0.01 nm. In this case, the sensitivity of the laser deformograph with an arm length of 52.5 m is equal to Δl / l = 0.01 nm / 52.5 m ~0.2 · 10–12, and that of the laser deformograph with an arm length of 17.5 m is ~0.6 · 10–12. The obtained data from laser deformographs through cable lines enter the laboratory room where, after preliminary processing (filtration and decimation), they are recorded on solid carriers of the computer-aided complex with the subsequent organization of a database of experimental data.
In 2012–2013, in the underground mine of PJSC "Priargunskoe Production Mining and Chemical Association" in the location with the coordinates 50° 4.726’ N and 118° 5.726’ E, see Fig. 1, at a depth of about 300 m a laser deformograph with a measuring arm length of 50 m, optical part of which is assembled according to the scheme of a modified Michelson interferometer and a frequency-stabilized helium-neon laser was installed and mounted on two concrete blocks rigidly connected to the main reservoir of the mine. A corner reflector is mounted on one of the concrete blocks, and a central assembly of the Michelson interferometer consisting of a frequency-stabilized helium-neon laser (MellesGriot), which provides frequency stability in the tenth digit, an extreme control system (recording system and resonant amplifier), and other structural and optical elements of a laser deformograph were mounted on the other block. Between the two concrete blocks, the laser beam was propagated along the sealed beamguide consisting of docked pipes with an internal diameter of 9 cm. After the instrument was installed for several days, test measurements of variations in the level of deformation of the earth’s crust were made. The obtained experimental data were accumulated on a solid carrier with a sampling rate varying depending on the experimental tasks in the range of 1–2500 Hz, and further processed to determine the technical characteristics of the laser deformograph, which were reduced to the following: the accuracy of the displacement measurement is at background level and is the value of the order of 0.01–0.1 nm, and the sensitivity threshold is ~ 1.2 · 10–12. At the end of the experimental tests, the laser deformograph was subjected to preventive maintenance and then launched into a mode of continuous measurements of variations in the deformations of the earth’s crust with technical interruptions associated with the preventive and repair work of individual units of the instrument. In real time, the experimental data were continuously fed to the data collection center located on the surface of the Earth and recorded on a hard drive of the computer into serial data files lasting 1 hour with a sampling frequency of 1000 Hz with reference to the exact time with an accuracy of 1 ms. After the file was saved on the computer, it became available via telecommunication lines to the employees of institutes located in Khabarovsk and Vladivostok.
At the end of 2013, a laser deformograph of the classical type with a measuring arm length of 6 m was constructed in accordance with the scheme of the modified Michelson interferometer in Taiwan in the location with coordinates 22° 52.534’ N and 120° 12.603’ E (see Fig. 1) and using a frequency-stabilized helium-neon laser. The measuring arm of the instrument is oriented with a deviation of 1.50 from the east-west axis. The applied electron-optical recording system makes it possible to measure the change in the distance between two support cabinets with an accuracy of 0.1 nm, which, with a measuring arm length of 6 m, provides the sensitivity of the laser deformograph about 2 · 10–11. Measurements of variations in the deformations of the earth’s crust at the location of the instrument were carried out for two weeks, with the experimental data recorded on hard computer carriers, which were then placed in a database of experimental data at the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences (Vladivostok).
As it was mentioned above, the experimental data from all measuring instruments were placed in the experimental data base of the Pacific Oceanological Institute of the Far-Eastern Branch of the Russian Academy of Sciences (Vladivostok), which were later processed using a specially created package of DEFORMOGRAF application software consisting of a full range of spectral and statistical estimation programs. When processing the experimental data obtained on the described laser deformographs in December 2013, we are going to analyze the results obtained from the point of view of studying the features of the manifestation of regional and planetary processes on the readings of these instruments in the infrasonic range, beginning with tidal components up to oscillations with a period of 1 s.
ANALYSIS OF THE RECEIVED EXPERIMENTAL DATA
Given that the laser deformograph operated at Taiwan’s testing site for about two weeks (from December 05 to December 14, 2013), and even with its adjustment and debugging, we processed and analyzed the data of all laser deformographs only during this period of observation. In this part of the article, we will focus on the results of a regional nature that were obtained by processing the data of specific laser deformographs, and also outline general patterns in the behavior of signals of different frequency ranges of those natural processes that characterize the planet as a whole. Table 1 shows some processing results, namely: the results of processing over the tidal range (24–1 h), the results of processing on the range of natural oscillations of the Earth (it can also be said about the sea processes of the seismic range, etc., 1 h – 1 min), the processing results for the range of "Infra-gravitational noise of the Earth" (10–0.5 min), the results of processing on the microseismic range (30–2 s). When comparing the amplitudes of diurnal and semidiurnal harmonics on all three polygons, we can state as follows:
1) for laser deformographs located near the sea (Schultz Cape and Taiwan), relative amplitudes, i. e., deformation ε, for diurnal harmonics are comparable 0.68 · 10–6 and 0.47 · 10–6, as well as for semidiurnal harmonics – 0.39 · 10–6 and 0.20 · 10–6;
2) for a laser deformograph located in Transbaikalia, these relative deformations are almost an order of magnitude smaller. The first laser deformographs were near the sea, and the third laser deformograph was on the continent. Large deformation amplitudes indicate the loading effect of the sea tide on the level of microdeformations of the earth’s crust in this frequency range.
In the higher frequency range (1 hour – 1 minute) the following can be noted. In the range of periods from the values corresponding to one spheroidal mode 0S2, up to the values corresponding to the other spheroidal mode 0S0, there are no general regularities, i. e. in this range of periods there are no spheroidal and torsional tones recorded and the overtone of the Earth’s natural oscillations due to the fact that during this period of observations on the Earth there were no earthquakes of sufficient power that could excite the modes of a sufficiently high amplitude necessary for recording by all the laser deformographs indicated above.
In the records of all laser deformographs, the areas with powerful quasi-harmonic oscillations corresponding to periods of about 11 min of 22.7 s are identified (see Fig. 2). One can also identify some powerful general oscillations in the range of periods from 1.5 to 4.5 min. Thus, Fig. 3 shows the spectra of the sections of the records of the laser deformographs of Krasnokamensk, Schultz Cape, Taiwan, from which peaks can be distinguished in the periods of 4 min 16 s (Krasnokamensk), 2 min 50.7 s (Krasnokamensk), 1 min 53.8 min (Krasnokamensk), 2 min 50.7 s (Schulz Cape), 2 min 16.5 s (Taiwan). Furthermore, for the pair of deformographs of Krasnokamensk-Taiwan, a common powerful peaks in periods of 8 min 32 s, 3 min 24.8 s, 3 min 47.6 s can be found. With more careful analysis, it can be asserted that the periods of the allocated oscillations vary in a certain interval. For the considered range of periods (1.5–4.5 min):
1) Krasnokamensk – from 3 min 24.8 s to 4 min 16.0 s, from 2 min 50.7 s to 3 min 06.2 s, from 1 min 37.5 s to 2 min 16.5 s;
2) Schultz Cape – peaks with periods of about 2 min 50.7 s and 1 min 25.3 s;
3) Taiwan – from 3 min 24.8 s to 4 min 16.0 s, from 1 min 50.7 s to 2 min 16.5 s.
On the basis of the latter, it is possible to single out general perturbation groups in the period range of 3 min 24.8 s – 4 min 16.0 s (Krasnokamensk, Taiwan), 2 min 50.7 s – 3 min 06.2 s (Krasnokamensk, Schultz Cape), 1 min 25. 3 s – 2 min 16.5 s (Krasnokamensk, Schultz Cape, Taiwan).
It is very difficult to explain the existence of such powerful perturbations, and even with periods that vary within fairly wide limits. The only reasonable source of perturbations can be associated with atmospheric processes, possibly with edge atmospheric waves, the surface layers of the atmosphere that arise. This assumption can be confirmed by the results shown in Fig. 4, obtained by processing the data of the Taiwan laser deformograph. As can be seen from the figure, the powerful perturbation almost along the arc has changed from a period approximately equal to 9 minutes to a powerful perturbation with a period of about 3 minutes 40 seconds for 6 hours, and then almost symmetrically within 6 hours has changed along an arc from a period equal to 3 min 40 s up to a powerful perturbation with a period of about 9 minutes. It is clear that this perturbation can only be connected, at first glance, with atmospheric processes, possibly with orographic waves. With a more complete analysis of the data of the Taiwan laser deformograph, it was found that such changes in the periods from smaller to larger and backward were observed repeatedly. Even more incomprehensible perturbation is isolated from the records of the Krasnokamensk laser deformograph. Fig. 5 gives an example of one of the selected perturbations. The duration of these perturbations is about 22 minutes, 3 hours, 8 hours and 24 hours, which, apparently, is due to technogenic deformation perturbations caused by human production activity in the mine. The amplitude of these perturbations is comparable or even greater than the amplitude of the tidal components.
Next, we will concentrate on the microseismic range (2–30 s). The main source of perturbations is associated with sea surface waves (wind waves or swell). The Schulz Cape is washed by the waters of the Sea of Japan. Therefore, in this range of periods, the main source of perturbation of microseisms is the sea wind waves or swell. With a relatively calm sea, characteristic sea surface waves for the observation point have periods of 5–6 s, which are transformed into elastic oscillations of the bottom at the appropriate periods in the shallow and swampy zones. In the storm conditions, the period of these waves can reach 12–13 s. Fig. 6 shows an example of the recording spectrum of a laser deformograph installed at the Schultz Cape, where a strong perturbation with a period of about 10–11 s, related to the microseismic range, is evolved and caused by swell waves. Spectral processing of records of the Krasnokamensk laser deformograph in the microseismic range distinguishes peaks in the range of periods of 6–6.5 s, 3–3.2 s, 4–4.2 s (see Fig. 7), which can be caused by various wave sources, primarily associated with wind waves of the Baikal Lake, as well as the nearby Umykai Lake. Apparently, oscillations with periods of about 6 and 3 s are associated with the wind waves of the Baikal Lake, and about 4 s – with the wind waves of the Umykai Lake. In Taiwan, the measurements were made in the period of almost complete absence of wind waves, so the spectral processing revealed maxima of the microseismic range with a period of about 3.5 seconds, which are caused by local wind waves. Almost in this range of periods, one can single out a powerful perturbation having a quality factor of the order of 350 at frequencies corresponding to the periods 21.18 and 10.6 s, which are clearly not related to wind waves.
On the basis of classical-type laser deformographs, a photonic antenna "Russia-Taiwan" was created, designed to study the nature of deformation processes in the frequency range from 0 (conditionally) to 1000 Hz with accuracy of 10–11 to 10–12. The short-term measurements of variations in the level of deformation of the earth’s crust confirmed its great prospects in studying the nature of deformation processes in the tidal range, in the range of natural oscillations of the Earth and in the microseismic range. One of the most important directions of the use of this photonic antenna is connected with the tasks of dividing the registered processes into regional and planetary ones, as well as the processes related to the interaction of geospheres in the transition zone of the atmosphere-hydrosphere-lithosphere system.
The research was carried out with partial financial support of the FEB of RAS, "Far East" program, a joint research projects competition of the Far East Branch of the Russian Academy of Sciences and the Ministry of Science and Technology of Taiwan.