This paper describes the results of monitoring wave processes in the geospheres using laser interference instruments, a weather station, a seismometer, and other measuring devices. Processing in situ data revealed general patterns in seismic events and variations in the hydrosphere and atmospheric pressure. Laser strainmeters and a seismometer were used to identify natural and anthropogenic seismic activity. A laser nanobarograph and strainmeters allowed us to detect baro-deformation interactions. Processing data from supersensitive detectors of hydrosphere pressure variations, a tide gauge, and temperature sensors revealed regional features of marine wave processes.

This work is devoted to an experiment studying the regularities of the propagation of hydroacoustic low-frequency signals in the conditions of the sea at intermediate depth and deep in terms of their transformation into vibrations in the upper layer of the Earth’s crust. This experiment belongs to the field of acoustic tomography and is aimed at solving the problems of non-contact methods for studying the geological structure of the shelf areas of the World Ocean. The novelty and uniqueness of the work lies in the use of a harmonic low-frequency hydroacoustic signal with a frequency of 22 Hz of high power, capable of creating Rayleigh surface waves at the “water–bottom” interface. The surface waves propagating at the bottom are registered by a coastal laser-interference measuring system capable of recording deformations in the upper crustal layer with an accuracy of 0.01 nm. The experimental results showed that the radiated hydroacoustic energy is not localized in the liquid half-space and propagates predominantly according to the law close to spherical divergence, even when the shelf depth is comparable to the wavelength of the radiated signal.

Based on the field data of laser interference devices obtained on the shelf of the Sea of Japan, the interaction of internal sea waves with the bottom and the transfer of energy from the sea wave to the seismic acoustic wave were studied. It has been established that when internal waves move from the depth dump to the surf zone, they transform, and their period decreases. When the energy of the internal wave is transformed into elastic bottom vibrations, the flow density is estimated to spread evenly over a shelf about 30 km wide. Taking into account the maximum amplitudes of elastic bottom vibrations caused by offshore internal waves, the density of the seismic energy flux will increase by 2–3 orders of magnitude and will be comparable to the density of the seismic energy flux caused by surface sea waves.

The article describes a hard- and software controlled complex for gas-strain monitoring, consisting of stationary laser strainmeters and a laser nanobarograph, a stationary gas analyzer, and a weather station installed at Shultz Cape in the Sea of Japan; and a mobile shipboard complex, consisting of a gas analyzer and a weather station installed in a scientific research vessel. In the course of trial methodological measurements on these systems, general patterns were identified in the dynamics of greenhouse gases and deformation of the Earth’s crust in the range of diurnal and semi-diurnal tides, and also in the range of ultra-low frequencies, caused by atmospheric wave processes and, possibly, individual tones of the Earth’s eigen oscillations.

Methodological and technical possibilities of monitoring temperature fields along a 1000-km track in the Sea of Japan using acoustic thermometry are presented. The proposed tomographic method for monitoring the dynamics and structure of waters is based on emission and reception of complex phase-shift keyed signals on a diagnosed path with determination of the propagation time along various ray trajectories with further measurement of the speed of sound and temperature. The physical prerequisites for practical use of thermometric studies at large distances are based on the acoustic “mudslide” effect: the phenomenon of the transition of acoustic energy from the bottom shelf area to an underwater sound signal of the deep ocean. A high-precision system of acoustic thermometry on the basis of tomographic schemes with mobile and stationary hydroacoustic emitters and receiving systems is proposed and tested with the example of the Sea of Japan.

The paper describes a planetary laser interferometric seismoacoustic observatory consisting of six stationary unequal arm laser strainmeters. Based on the triangulation method, the fundamentals of direction finding of various infrasound disturbances at any planetary distance have been developed. The authors show that in addition to determining locations of the occurrence of the recorded disturbance, using data from spatially separated laser strainmeters, it is possible to determine the nature of these signals’ divergence and, also, the loss of their energy in the propagation medium. The creation of the planetary laser interferometric seismoacoustic observatory, consisting of five stationary single-coordinate laser strainmeters and one two-coordinate laser strainmeter, united into a single measuring network with an accurate time clock TRIMBLE 5700 that is capable of recording displacements on their bases with an accuracy of 10 pm in the frequency range from 0 (conventionally) to 1000 Hz and two auxiliary laser strainmeters, will allow us to determine, at any planetary distance, the primary source of deformation infrasound disturbances with primary amplitudes from 100 nm.

The results of analyzing the in-situ data of shear stratified flow measurements on the shelf of the Sea of Japan are presented. Study of critical zones and layers is performed in terms of the dimensionless Froude and Richardson numbers. It is shown that during the propagation of high-intensity internal bores, sufficiently long (up to several hours) time intervals occur, which are characterized by a supercritical Froude regime, when active generation of short-period internal waves of large amplitude is predicted and takes place. The statistics of the Richardson numbers shows that with the lower bound on the probability in the layer of flow measurements during the observation period, shear instability can occur in 15

By processing satellite data on the total electron content on a track between GLONASS, GPS, and ground receiving stations located in Primorsky Krai of Russia, disturbances of an electron layer with periods from 5 to 45 min, which are caused by natural atmospheric fluctuations, were identified. They affect the sea surface and are responsible for aquatic fluctuations with periods from 5 to 40 min.

During the propagation of the Hinnamnor typhoon from September 5 to 6, 2022, swell waves were recorded that arrived at the recording point 20 h before the typhoon entered the Sea of Japan. While analyzing the field data of the laser meter of fluid pressure variation, it was possible to calculate the area of the formation of the main group of swell waves generated by the propagating typhoon and to localize the region of generation of forerunner waves and also to describe the mechanisms of their formation and propagation.

We propose interpreting the vertical structure of waters not only in space but also over time, taking into account the continuous variability of the ocean and the independence of temperature and salinity parameters. This approach allows us to consider, in real conditions, the entire spectrum of short- and long-term extrema of both characteristics, either separately or together at the same depth. Vertical distributions of temperature and salinity transform separately and independently of each other under the influence of heat and freshwater budgets, which change at different time scales. Each of the parameters has its own active layers with corresponding time scales. Changes in the signs of heat and freshwater budgets and subsequent changes in the characteristics of the surface layer cause the appearance and disappearance of separate extrema of temperature and salinity in the water column. Using a salinity field as an example, we have shown that each of the extrema, in their vertical distribution from the near-surface to the intermediate depths, is a temporary phenomenon with various lifetime scales and is located at the lower boundary of the corresponding active layers. In some areas of the ocean, temperature and salinity extrema exist together at the same depth. Volumes of water with such characteristics and explicit boundaries should be considered water masses.

In this paper, the authors present and analyze the geoacoustic digital seabed model they developed, which is a digital description of the water column characteristics, seabed topography, and information about sediments and rocks (their composition and elastic properties) for Peter the Great Bay, the Sea of Japan. The model consists of four relief layers, a foundation and three layers of bottom sediments, and also contains the velocities of longitudinal waves in rocks and statistical characteristics of the sound velocity distribution in the water layer for three seasons. Acoustic characteristics of geological structures are based on seismoacoustic studies, sediment lithology, and laboratory measurements of rock samples collected onshore. The velocities of longitudinal and transversal waves and also the density of the sediments were calculated from their empirical dependencies on the granulometric composition of bottom sediment samples over an area of about 800 km2. In a limited area of the shelf (approximately 130 km2), high-frequency acoustic studies were carried out using echo sounders, and the longitudinal wave velocities of the top sedimentary layer were determined. Porosity, density, longitudinal, and transverse wave velocities in bottom sediments were calculated using empirical models with a normal coefficient of reflection from the seabed. A comparison was made of the results of calculating the elastic properties of the seabed using various methods.

The explosive eruption of the Hunga Tonga-Hunga Haapai volcano occured on January 15, 2022 at 04:02 UTC led to generation of covolcanic ionospheric disturbances that spread over long distances. Using GNSS data obtained at permanent stations of the IGS network and sites located on the territory of Primorsky Krai, the search and analysis of ionospheric disturbances over the territory of Primorsky Krai and adjacent areas was performed. The velocity of the covolcanic ionospheric disturbances recorded over the Primorsky Krai reached about 340 m/s, and the average amplitude was equal to 1.0 TECU. The results obtained from GNSS-data were also compared with the results of observation data obtained by a laser strainmeters (oriented in the directions "north – south" and "east – west") and a laser nanobarograph located at the Schultz Cape (the south of Primorsky Krai). As a comparison result, time delays between the moments of fixation of disturbances in the troposphere and ionosphere were found. The delay between the first peaks of disturbances was equal to ~50 min.

This paper describes the possibility of using a laser interference device as a hydroacoustic signal receiver. A supersensitive detector of hydrosphere pressure variations, created based on the equal-arm Michelson interferometer, was used in hydroacoustic studies. These experimental studies were conducted using hydroacoustic and seismoacoustic radiators as a signal source. A hypersensitive sensor of hydrosphere pressure variations was used as a signal radiator. The device received a signal from both hydroacoustic and seismoacoustic radiators.

This paper presents a discussion on observations of nonlinear internal waves (NLIWs) in the coastal zone of the Sea of Japan, based on the mooring of thermostring clusters in different seasons of 2022. For statistical evaluation of the frequency of event occurrence and determination of NLIW movement direction, we use our observations of the past 12 years. We present the NLIW structures, observed in spring, summer, and autumn of 2022, which are typical for this shelf area. Two types of nonlinear waves are described—solitary and undular bores, with or without strong vertical mixing behind the front. We demonstrate spatial transformation of an undular bore as it moves over the shelf. A mathematical model based on the second-order shallow water approximation is proposed for numerical simulation. To simplify calculations, the authors limit themselves to two- and three-layer shallow water models. We investigate the possibility of spatiotemporal reconstruction of internal nonlinear structures between thermostrings using experimental data and proposed models. The authors show that at distances of up to several kilometers between thermostrings, the wave fields of strongly nonlinear and nonstationary structures can be successfully reconstructed. Water flow induced by NLIWs can be reconstructed from the data of even one thermostring.

Transformations of bottom pressure variations generated by infragravity waves into displacements of the upper layer of the Earth’s crust have been quantitatively assessed based on the experimental data obtained with a laser meter for hydrospheric pressure variations and two laser strainmeters. The relationship between the coefficient of bottom pressure transformation into elastic vibrations of the Earth’s crust and the infragravity wave period has been determined.

This paper describes the design and principle of operation of a 20 m laser strainmeter of unequal-arm type created on the basis of a Michelson interferometer and frequency-stabilized helium–neon laser. The interferometry methods used allow the measurement of the displacement of an Earth’s crust section on the base of the laser strainmeter with an accuracy of 30 pm in the frequency range from 0 (conventionally) to 1000 Hz. This laser strainmeter, when connected to an accurate time system providing an accuracy of 1 μs, should structurally become a part of the laser interferometric seismoacoustic observatory, consisting of spatially separated laser strainmeters installed in various regions of Russia.

This article explores the features of using hydroacoustic methods to measure and monitor climate-induced temperature variations along acoustic paths in the Sea of Japan. It delves into effective techniques for controlling and positioning of deep-sea autonomous measuring systems (DSAMS) for diverse applications. Theoretical and experimental findings from research conducted in the Sea of Japan in August 2023 along a 144.4 km acoustic route under summer–autumn hydrological conditions, including the aftermath of the powerful typhoon “Khanun”, are presented. The main hydrological regime characteristics for this period are compared with data obtained in 2022. This study explores the transmission of pulsed pseudorandom signals from a broad shelf into the deep area of the sea, with receptions occurring at depths of 69, 126, 680, and 914 m. An experiment was conducted to receive broadband pulse signals centered at a frequency of 400 Hz, located 144.4 km from the source of navigation signals (SNS), which is positioned on the shelf at a depth of 30 m in waters that are 45 m deep. A system of hydrophones, deployed to depths of up to 1000 m, was utilized to capture signal data, allowing for prolonged recording at fixed depths or during descent. An analysis of the experimentally acquired impulse characteristics revealed a series of ray arrivals lasting approximately 0.5 s, with a peak consistently observed across all depths. Findings from both full-scale and numerical experiments enabled the assessment of impulse characteristics within an acoustic waveguide, the calculation of effective signal propagation speeds at varying depths, and the development of conclusions regarding the viability of tackling control and positioning challenges for DSAMS at depths reaching up to 1000 m and distances spanning hundreds of kilometers from control stations.

In the paper, we analyze laser strainmeter data for the period from 2014 to 2022 to identify deformation anomalies that led to the generation of tsunamis in the area of the Japanese Islands. It is impossible to determine the main characteristics of a tsunami from the deformation anomaly registered by the laser strainmeter, but it is possible to calculate the seabed displacement in the epicenter of a tsunami formation, which causes the tsunami. We have established that the relationship between the registered deformation anomalies and the seabed displacement in the tsunami source in the area of the Japanese Islands is similar to the same relationships found in other regions of the Earth (Indonesia, Latin America, and the West Coast of North America). This result allows us to assert that such a relationship should be typical of any region of the Earth. The obtained results are aimed at solving the problem of reliable short-term tsunami forecasting, which allows for the avoidance of false alarms that lead to significant socio-economic damage.

When processing satellite data of total electron content on the route between GLONASS satellites, GPS and receiving stations located on earth in the Primorsky Territory of Russia, infragravity disturbances caused by their own fluctuations of the atmospheric layers of the Jap-Sea region, which have a loading effect on the Earth’s crust and the sea/ocean surface, generating fluctuations in them for the corresponding periods, were identified.

On the basis of experimental data from laser strainmeters, a laser nanobarograph, and a laser meter of hydrosphere pressure variations, we studied inter-geosphere interaction in microseismic range (2–20 s) and in minute range (4–17 min). We established general patterns of transformation of the Earth’s crust upper layer oscillations into atmospheric oscillations, and atmospheric oscillations—into oscillations of the Earth’s crust upper layer in the specified ranges. Besides, we show that transformation coefficient has seasonal dependence, associated with different elastic characteristics of the Earth’s crust upper layer in winter and summer due to negative winter temperatures and high positive summer temperatures, and also different moisture saturation of the soils.