B. W. Levin

Manifestations of the tsunami on November 15, 2006, on the central Kuril Islands and results of the runup heights modeling

ISSN 1028-334X, Doklady Earth Sciences, 2008, Vol. 419, No. 2, pp. 335–338.

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 Kuril tsunamis of November 15, 2006, and January 13, 2007: Two trans-pacific events

On December 26, 2004, a catastrophic earthquake ( M w = 9.3) occurred near the northwestern coast of Sumatra Island in the Indian Ocean. The tsunami generated by this event caused unprecedented destruction (with more than 226 000 casualties) and was one of the worst natural disasters in human history [15]. Analysis of this event performed at the Institute of Oceanology, RAS immediately after this event, revealed firstly, that the source of the earthquake of December 26, 2004, was located in a large seismic gap region where strong earthquakes had not been observed for more than 150 years; and secondly, that a similar seismic gap is located in the central part of the Kuril Kamchatka Subduction Zone [1, 4].

Monitoring of the eruption of the Sarychev Peak Volcano in Matua Island in 2009 (central Kurile islands)

In June 2009, one of the greatest eruptions of the Sarychev Peak volcano in Matua Island (48°06′ N, 153°12′ E) for the recent historical period occurred. With the help of satellite sounding methods, the first signs of volcanic activity were recorded and all the stages of the explosive eruption were traced. During the expeditionary investigations in the active volcano, unique data on the character of the eruption were obtained. The volume of erupted material was 0.4 cubic km, which lead to an increased area of Matua Island by 1.4 square km. The GPS observation station set at the distance of 7 km from the volcano recorded the rapid displacement of the Earths’s surface during the first two days of the active phase of eruption. This eruption of the Sarychev Peak volcano occurred 2.5 years after the catastrophic Simushir earthquakes in the period of intensive relaxation of stresses in the middle of the central part of the Kurile island arc.

Manifestations of the Nevelsk and Gornozavodsk earthquakes of 2006–2007 in the dynamics of gryphon activity of the Yuzhno-Sakhalinsk gas-water-lithoclastic (Mud) volcano

Mud volcanism is a specific natural phenomenon, which is very interesting for geologists, geophysicists, and people who are fond of nature. It is assumed that mud volcanoes can be indicators of geodynamic processes in the Earth’s interior and serve as forerunners of tectonic earthquakes. In this work, we present the data of field observations of the Yuzhno-Sakhalinsk mud volcano during the preparation period and realization of strong seismic events in the southern part of Sakhalin Island. A possible interpretation of the distinguished anomalies in the volcano activity is suggested. Mud volcanoes are natural fluid dynamics systems, in which intense transport of energy and matter from the Earth’s interior to the surface occurs. At present there is no unambiguous concept about the existence or absence of a correlation between mud volcano activity and natural seismicity. The character of such a possible correlation is also unknown: it is a precursor of a response? This ignorance is due to a lack of the necessary empirical material that can be obtained during long-term observations.

General regularities in the distribution of seismic events on the Earth and on the Moon

In this work, characteristic features of seismic event distribution by latitudes and depth are compared for the Earth and the Moon. It is shown that earthquakes and moonquakes are distributed similarly by latitudi� nal belts. The problem of earthquake epicenter distribution by latitudinal belts of the Earth was stated in the 1960s. Firstly, only the distribution of strong earthquakes ( M > 7) was studied. In the early works [5, 8], hetero� geneity in events distribution by latitudes was noted. A substantial progress was achieved in [9]. On the basis of a Chinese catalogue of strong earthquakes in 1897– 1980 (1165 events), it was noted that the energy released after seismic events is almost zero for high lat� itudes and the two main peaks of seismic activity are located in middle latitudes and are divided by a zone of less activity near the equator. The papers of the authors of the present communi� cation contain the results of the analysis of earthquake latitudinal and depth distributions [2, 3]; however, comparative analysis of earthquake and moonquake distributions taking into account latitude, depth, and energy of events has not yet been undertaken. The aim of the present work is to present the results of such analysis and to comment on the possible relationship of the seismic process with exogenous effects on both the Earth and the Moon. Analysis of a wide spectrum of seismic events was carried out on the material of the ISC catalogue [6] (more than 200 000 events with M ≥ 4) on the basis of the approached elaborated in [2]. It was stated that seismic activity of the planet is almost absent in the poles and in polar caps of the Earth and reveals clearly expressed maximums in middle latitudes of the North� ern and Southern Hemispheres and the stable local minimus near the equator. These distributions by lati� tudinal belts of the Earth are characteristic for a num� ber of seismic events and for released energy as well. Because of the fact that most earthquakes are concen� trated in the boundaries of lithospheric plates, in [2] normalizing of earthquake number and released energy by length of the lithospheric plate boundaries in every single latitudinal belt was used. Such a nor� malizing gives us a power of this area of a plate bound� ary (average number of earthquakes generated per every 100 km of plate boundary). Using of this charac� teristic, the physical sense of which is clear, allows us to compare seismic activity of latitudinal belts in vari� ous parts of the world. The total number of studied events was subdivided into several subgroups by values of magnitude ranges (MRs: 4.0 ≤ Mb < 4.5; 4.5 ≤ Mb < 5.0; 5.0 ≤ M b < 5.5; 5.5 ≤ M b < 6.0; 6.0 ≤ M b ).

Depth distribution of earthquakes through latitudinal belts of the Pacific region: General trends

The geological sciences have recently demonstrated a tendency to move away from considering the Earth as an immobile system and from explaining global seismic processes only by endogenic interrelationships. Nowadays, some geologists take into consideration external forces and irregularities in the orbital parameters of the Earth in the Earth‐Sun‐Moon system when analyzing seismic processes [2]. The study of global regularities in the latitudinal distribution of earthquake foci revealed their distinct irregularity. It has been shown [3, 4, 6] that seismic activity is practically absent at polar and near-polar latitudes and rapidly increases in the middle latitudes to reach a maximum at 40 ° ‐50 ° N and 20 ° ‐30 ° S with a stable local minimum along the equator. The quantitative distribution of seismic events through different latitudes with account for hypocenter depths at four depths intervals is considered in [7], although its authors performed no quantitative analysis of their two-dimensional distribution (through depths and latitudes) and two-dimensional distribution of released energy.

Cyclic variations in the Earth’s flattening and questions of seismotectonics

For more than a decade, the global network of GPS stations whose measurements are part of the International GPS Service (IGS) have been recording cyclic variations in the radius vector of the geodetic ellipsoid with a period of one year and amplitude of ~10 mm. The analysis of the figure of the Earth carried out by us shows that the observed variations in the vertical component of the Earth’s surface displacements can induce small changes in the flattening of the Earth’s figure which are, in turn, caused by the instability of the Earth’s rotation. The variations in the angular velocity and flattening of the Earth change the kinetic energy of the Earth’s rotation. The additional energy is ~1021 J. The emerging variations in the flattening of the Earth’s ellipsoid lead to changes in the surface area of the Earth’s figure, cause the development of deformations in rocks, accumulation of damage, activation of seismotectonic processes, and preparation of earthquakes. It is shown that earthquakes can be caused by the instability of the Earth’s rotation which induces pulsations in the shape of the Earth and leads to the development of alternating-sign deformations in the Earth’s solid shell.

Effect of the Earth’s rotation on subduction processes

The role played by the Earth’s rotation is very important in problems of physics of the atmosphere and ocean. The importance of inertia forces is traditionally estimated by the value of the Rossby number: if this parameter is small, the Coriolis force considerably affects the character of movements. In the case of convection in the Earth’s mantle and movements of lithospheric plates, the Rossby number is quite small; therefore, the effect of the Coriolis force is reflected in the character of movements of the lithospheric plates. Analysis of statistical data on subduction zones verifies this suggestion.

The first identification of hydrogeochemical indicators of mud volcanic activity

Hydrogeochemical monitoring has been implemented at a mud volcano for the first time in the world. Measurements were carried out during the field season of 2015 at five gryphons of the South Sakhalin mud volcano with various degrees of activity. Statistically significant differences in the chemical compositions of mud-volcano waters from different gryphons are established. These differences are determined by the activity of the gryphons.