The Volcanogenic Tsunami on January 15, 2022, Based on the Records of Deep-Ocean DART Stations

Doklady Earth Sciences - 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...     

Contribution of horizontal deformation of the seafloor into tsunami generation near the coast of Japan on March 11, 2011

Based on the USGS slip distribution data (Finite Fault Model), the vector field of the seafloor deformation in the source of the tsunami that occurred on March 11, 2011, was calculated. The field of seafloor deformation and distribution of depths in the area of the source were used for reconstruction of the initial elevation of the water surface in the tsunami source. It was found that the contribution of horizontal deformations into the amplitude of the initial elevation, into the displaced water volume, and into the potential energy of the initial elevation is at about 20–25%. Within the framework of the linear theory of long waves, numerical simulation of evolution of the initial elevation was made. The simulation results were compared to the signals recorded by the four deep water stations DART which were the nearest to the source. It was shown that account of the horizontal deformation of the seafloor provides a more precise coincidence between the model and real data. Insignificant differences in arrival times of the model and real signals were interpreted as manifestation of phase dispersion and finite duration for the seafloor deformation to form.     

The role of bottom friction in models of nonbreaking tsunami wave runup on the shore

The role of bottom friction in the runup of nonbreaking long waves on the shore is analyzed. The case of the normal incidence of monochromatic waves is considered. The relief of the model region consists of an even horizontal bottom area conjugated with a flat slope. The energy dissipation is estimated as the work of bottom friction forces over the wave field obtained using the known analytical solution based on the Carrier-Greenspan transforms. Estimates of energy losses for waves whose periods are typical for tsunami waves have been obtained. The energy dissipation is shown to be not concentrated in the shore line area as a rule. The question about the practicability of using partially reflecting boundary conditions on the coast to take into account the bottom friction in large-scale models of tsunami propagation is considered.     

Verification of the multi-chamber model of radioactivity migration in reservoirs

A multi-chamber model of radioactivity migration in reservoirs was developed. It describes transport of radioactive substances in water and in bed sediments taking into account sorbtion of radionuclides on suspended particles. The model provides higher resolution than simplified chamber models do. At the same time, unlike complex two- or three-dimensional dynamic models, it does not require hard-to-obtain data such as detailed data on bathymetry, currents and winds. The model was included into the Sybilla program code that was developed in the framework of the Rosatom project called PRORYV. The model was verified against the observed data on the contamination of the Kiev Reservoir with ¹³⁷Cs in 1986.     

Horizontal Motions of Water in the Vicinity of a Tsunami Source

Because it is based on an initial seismic analysis and preset criteria, tsunami forecast often fails in assessment of tsunami danger. The level of danger can be determined more or less reliably only when observed sea level data became available. Along with the sea level data, i.e., vertical motions of free water surface, we suggest considering horizontal motions of water that accompany the formation and the propagation of a tsunami. The amplitude of horizontal motions is normally much higher than the amplitude of the vertical motions. Detection of the horizontal motions may provide tsunami warning centers with additional in situ data that can be used for estimation of tsunami strength. In this study, taking the 2011 Tohoku-Oki event as an example, horizontal motions of water in the vicinity of the tsunami source are theoretically examined by means of dynamic and static numerical models developed within the framework of linear shallow-water approximation. It is shown that in the vicinity of the tsunami source within a wide area of about 0.5 million square kilometers, the amplitude of horizontal motions exceeded 10 m, whereas in some shallow-water areas the amplitude amounted to hundreds of meters. Possible methods of in situ detection of the horizontal motions are discussed.     

Biological Research in the Siberian Arctic Seas in Summer–Autumn 2019 (Cruise of the R/V Professor Levanidov)

Oceanology - The article presents the results of hydrobiological, ichthyological, trophological, acoustic, and genetic research aboard the R/V Professor Levanidov in the Chukchi, East Siberian,...     

Residual hydrodynamic fields after tsunami generation by an earthquake

The linear theory of long waves was applied to study horizontal motions of the water layer in a rotating ocean which appear after tsunami generation by an earthquake. The structures of residual potential and eddy fields are analyzed on the basis of the analytical solution of a model axisymmetric problem for an ocean of constant depth. The estimates of the horizontal displacements of water particles, velocity of the eddy current, and energy of the geostrophic eddy are calculated for typical conditions of the tsunami source. Particular features of the residual fields related to the existence of stable stratification are considered. Static and dynamic numerical models are described that allow us to calculate the residual potential field and its evolution related to the realistic events. The field of residual horizontal displacements of water particles for the catastrophic earthquake near the coasts of Japan on March 11, 2011, is calculated and analyzed.     

Gravity and Displacement Variations in the Areas of Strong Earthquakes in the East of Russia

The modern gravimetry methods are capable of measuring gravity with an accuracy of up to 10^–10 of the normal value, which is commensurate with the accuracy of the up-to-date methods of displacement measurements by satellite geodesy. Significant changes, e.g., in the coseismic displacements of the Earth’s surface are recorded in the zones of large earthquakes. These changes should manifest themselves in the variations of gravity. Absolute measurements have been conducted by various modifications of absolute ballistic gravimeters GABL since the mid-1970s at the Klyuchi point (Novosibirsk) in the south of the West Siberian plate. Monitoring observations have been taking place in the seismically active regions since the 1990s. In this paper we consider the results of the long-term measurements of the variations in gravity and recent crustal displacements for different types of earthquakes (the zones of shear, extension, and compression). In the seismically active areas in the east of Russia, the longest annual series of absolute measurements starting from 1992 was recorded in the southeastern segment of Baikal region. In this area, the Kultuk earthquake with magnitude 6.5 occurred on August 27, 2008, at a distance of 25 km from the observation point of the Talaya seismic station. The measurements in Gornyi (Mountainous) Altai have been conducted since 2000. A strikeslip earthquake with magnitude 7.5 took place in the southern segment of the region on September 27, 2003. The effects of the catastrophic M = 9.0 Tohoku, Japan, earthquake of March 11, 2011 were identified in Primor’e in the far zone of the event. The empirical data are consistent with the results of modeling based on the seismological data. The coseismic variations in gravity are caused by the combined effect of the changes in the elevation of the observation point and crustal deformation.     

Determination of the Parameters of a Submerged Source by Perturbations of the Liquid Surface Based on Machine Learning Methods

Doklady Earth Sciences - The inverse problem of generating surface waves in a liquid is to determine the parameters of the source of perturbations from the waves it creates on the liquid surface. A...