Based on experimental data on earthquakes under the oceans recorded with a 52.5-m laser deformograph, perspectives of the application of this device for determining the tsunami potential of earthquakes are substantiated. Since the velocity of propagation of tsunamigenic deformation anomalies is much greater than the velocity of these waves, the deformation method for determining the tsunami potential of earthquakes is the most promising technique for the tsunami warning services. The tsunamigenic deformation anomalies appear during different geodynamic processes. In general, these anomalies are related to earthquakes. The oscillations that appear during earthquakes in their focus cannot generate a tsunami. They only shake the bottom in the frequency range corresponding to a period of n ‐10 n s. The deformation anomalies are located in the extreme left frequency range and cannot be recorded by any (even broadband) seismographs. The hydrological installations used to record tsunamis are inefficient because the distance from the point of recording of a tsunami to its spreading on the shelf is virtually always small and there is not enough time for the efficient accomplishment of corresponding actions. Installations that can record deformation motions leading to tsunami generation are most promising for these goals because the velocity of deformation motion spreading in an elastic medium is more than one order of magnitude greater than the velocity of a tsunami. Laser deformographs of the horizontal and vertical types are the best devices for their recording and direction finding because of their main characteristics: the higher accuracy and wider frequency range of measurement of microdisplacement of the Earth’s crust using the deformographs (0.1 nm and 0‐1000 Hz, respectively). The dynamic range for measuring natural processes of the infrasound range is practically unlimited [1]. Currently, variations in the deformation rate of the Earth’s crust are monitored at the Cape Shultz station of the Pacific Institute of Oceanology using a 52.5-m horizontal laser deformograph with the characteristics listed above [2]. In this article, we analyze the records of the laser deformograph of the signals related to the tsunami

In the paper, we discuss the results of processing and analysis of field data obtained from a laser-based supersensitive detector during the registering of hydrosphere pressure variations on the seabed at various points of the Sea of Japan shelf. The main focus is the study of physical mechanisms of the occurrence of nonlinear hydrophysical disturbances in the range of gravity and infragravity sea waves classed as rogue waves, the amplitudes of which are more than twice the amplitudes of the bordering signals in this range of periods. It has been established that in the range of gravity/wind sea wave periods (2–20 s), similar disturbances were registered by the supersensitive detector of hydrosphere pressure variations. The paper explains the appearance of such nonlinear disturbances. In addition to single large-amplitude nonlinear perturbations, classical nonlinear disturbances, related to the “one sister”, “two sisters”, and “three sisters” rogue wave types were discovered. Their occurrence is associated with the interaction of gravity and infragravity sea waves in the zone of the recording equipment location. In the course of spectral processing of the obtained field data, the main modes of wind waves and infragravity sea waves responsible for the formation of the observed rogue waves were identified. The intermodal energy transfer in the observed wave packet resembles in its behavior the modified Fermi–Past–Ulam recurrence. In the lower frequency range, non-linear hydrophysical disturbances of the “sea hole” and “crest” type were found; the origin of which is associated with atmospheric processes.

In research into various hydrophysical and hydroacoustic wave processes, it is extremely important to know the regularities of their propagation in the sea at decreasing depths, especially in the shelf areas, and also to know the regularities of their transformation into seismoacoustic processes in the earth crust. In the course of the processing and analysis of the experimental data of our complex experiment, in this paper we investigate these regularities. In our experiment, we used a low-frequency hydroacoustic transmitter that generated harmonic oscillations at the frequency of 22 Hz and received hydroacoustic systems with a shore laser strainmeter. It was established that hydroacoustic waves, propagating at the shelf of decreasing depth, transform into seismoacoustic waves at the depth of the sea equal to or less than a half-length of the hydroacoustic wave. A comparison of the results of this work with earlier-obtained results allows us to state that such regularities should be inherent to all hydrophysical and hydroacoustic processes.

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.