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A theoretical analysis of wave motions that arise in the ocean under the action of traveling disturbances of atmospheric pressure is presented. Formulas for a fixed-depth ocean have been obtained to describe the manifestations of traveling disturbances of atmospheric pressure in bottom pressure variations. Formulas have been obtained for estimating the amplitude of free gravity waves generated in the ocean by a traveling atmospheric disturbance in the region of a sharp change in depth. Data from IRIS ground-based barographs and DART (Deep-ocean Assessment and Reporting of Tsunami) stations recording wave disturbances in the atmosphere and ocean caused by the explosive eruption of the Hunga Tonga–Hunga Ha'apai volcano on January 15, 2022 have been used to study the atmospheric Lamb wave manifestations in bottom pressure variations. A Lamb wave was shown to be manifested in bottom pressure variations with amplification and identical waveforms recorded by ground-based barographs and bottom pressure sensors. A Lamb wave with an amplitude of 500 Pa can excite surface gravity waves with an amplitude of 0.5 m in the region of a deepwater trench. [ABSTRACT FROM AUTHOR]

The manifestations of the Hunga Tonga–Hunga Haʻapai volcano explosive eruption on January 15, 2022, in the Pacific region were investigated using the data of the DART deep ocean sea level stations and the IRIS ground-based barographs. It was found that the atmospheric Lamb wave, caused by the explosion of the volcano, was formed at 04:27 UTC ± 4 min and propagated over the Pacific Ocean at a speed of 312 ± 4 m/s. It is shown that the leading distinct pulse recorded by all DART deep ocean sea level stations is a direct manifestation of the atmospheric Lamb wave. Theoretical estimations of the amplitude manifestations of the Lamb wave in the bottom pressure variations have been made. It is shown that the amplitude of bottom pressure variations in the deep ocean is a few times larger than the amplitude of pressure variations in the Lamb wave. Theoretical estimates of the amplitude of surface gravity waves excited in the ocean by traveling atmospheric disturbance passing a depth jump are carried out. [ABSTRACT FROM AUTHOR]

A physical analysis of the generation of tsunami waves by seismic movements of the ocean floor is presented. For a set of strong underwater earthquakes, the work done against hydrostatic pressure during coseismic displacements of the ocean floor and the available potential energy, tsunami energy, are estimated. It is shown that an insignificant part of the earthquake energy (from 0.004% for Mw = 7 to 0.16 % for Mw = 9) is transferred to the tsunami waves, while the work done against the hydrostatic pressure is comparable in absolute value to the earthquake energy estimated by the Kanamori formula. [ABSTRACT FROM AUTHOR]

A method is proposed for testing pressure gauges and z-accelerometers, installed in seafloor observatories. The method is based on the linear relationship between variations of the ocean-bottom pressure and the z-acceleration, observed during seismic movements of the bottom within the frequency band of "forced oscillations". Calculation of the boundaries of this frequency band is based on the ocean depth at the observatory site making use of explicit formulae. In the case of correct calibration of the gauges calculation of the ratios of power spectra of bottom pressure variations and the z-accleration within the band of "forced oscillations" yields constant values equal to the square ratio of the total mean pressure and the gravity acceleration. The conditions for application of the proposed method are formulated. [ABSTRACT FROM AUTHOR]

This paper describes a model for the generation of waves in the ocean by seismic bottom movements. A specific feature of this model is the use of curvilinear non-orthogonal sigma-coordinates. The results of numerical experiments aimed at studying the mechanisms of the generation of gravity waves by surface seismic waves propagating over the bottom are presented. [ABSTRACT FROM AUTHOR]

The Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) is a submarine cabled real‐time seafloor observatory network for precise earthquake and tsunami monitoring. Ten DONET observatories were in operation during the 2011 Tohoku‐Oki event near the Pacific coast of Honshu Island. Each observatory was equipped with an ocean bottom pressure gauge (PG) and a three‐component ocean bottom seismometer (OBS). A comparative analysis of the PG and OBS records revealed that shortly after seismic surface waves traversed the DONET region, free gravity waves were observed within the water layer. The period of these gravity waves was approximately 170 s, the peak‐to‐peak amplitude was approximately 3.5 cm, the length was on the order of 22 km, and the phase velocity was 134 m/s. We performed numerical simulations of the observed gravity waves using a combined 2D/3D numerical model. The ground motions required for the simulation were reconstructed from records provided by the DONET OBSs and the nearest ground‐based GPS stations. The synthetic bottom pressure variations are in good agreement with the DONET PG records. The synthetic displacements of the ocean surface throughout the simulation domain showed that the observed gravity waves were excited directly above the submarine slopes. Theoretical estimates and numerical experiments revealed the generation mechanism of the observed gravity waves. Plain Language Summary: During submarine earthquakes, the ocean floor shifts from its original position. Due to this displacement, a huge volume of water is moved, which can generate a destructive tsunami wave. However, earthquakes are accompanied not only by displacement of the ocean bottom in the epicentral area but also by the emission of seismic waves. These seismic waves are also capable of exciting waves in the ocean. For our study of this phenomenon, we used unique data from the Japanese Dense Oceanfloor Network System for Earthquakes and Tsunamis (DONET) observatories that were recorded during the Great East Japan Earthquake on 11 March 2011. Based on the records of the DONET seismometers, we reconstructed the movement of the bottom during the passage of a surface seismic wave. Then, using the obtained information, we simulated the movement of the water in the entire DONET area. The results of our simulation are in good agreement with the records of the DONET pressure gauges. The results also reveal that waves are only generated directly above steep submarine slopes during the passage of seismic waves. This study can help to identify tsunami wave signals in the records of bottom pressure gauges. Key Points: During the 2011 Tohoku event, seismic surface waves generated ocean surface gravity waves that were registered by the DONET observatoriesWe simulated the observed gravity waves using a combined 2D/3D numerical modelThe generation mechanism of the observed gravity waves was revealed based on theoretical estimates and numerical experiments [ABSTRACT FROM AUTHOR]

A numerical experiment for reproducing the generation of free gravity waves in the ocean by low-frequency surface seismic waves passing across the bottom is described. The dynamics of the bottom movement is reconstructed based on the real GPS data recorded during the disastrous Tohoku earthquake of March 11, 2011. Results of the numerical simulation show that horizontal movements of underwater slopes play a key role in the generation of free gravity waves. [ABSTRACT FROM AUTHOR]

The article presents study on gravity waves formed in the ocean by surface seismic waves during the earthquake in Japan on March 11, 2011. It mentions the use of Deep-ocean Assessment and Reporting of Tsunamis (DART) system for recording of tsunami waves in the ocean. It adds the Dense Ocean floor Network System for Earthquakes and Tsunamis (DONET) system developed by the Japanese Agency for Marine-Earth Science and Technology (JAMSTEC). It discusses gravity wave generation.

We have obtained an analytical solution to the problem of determining the initial elevation at the tsunami source, which was formed by small residual deformations of a flat sloping bottom. This solution, which is newly derived, is compared with the known analytical solution of an equivalent problem over a horizontal bottom. It is shown that applying an analytical solution over a horizontal bottom for calculating the initial perturbations in the sources of realistic tsunami provides sufficient accuracy. [ABSTRACT FROM AUTHOR]