B. V. Levin

Bimodal character of latitudinal earthquake distributions in the pacific region as a manifestation of global seismicity

Quantitative presentation of seismicity as the energy released per square unit during a time unit was for the first time introduced by M. Bath [1]. Application of this characteristic with a clear physical sense allows us not only to compare the seismic activity in different parts of the world but also to form concepts about the nature of the seismic process. The influence of external tidal forces on activation of the seismic process and magmatism has recently attracted the attention of geophysicists and geologists [2].

The tsunami on Sakhalin on August 2, 2007: Mareograph evidence and numerical simulation

Instrumental data on the tsunami registration on Sakhalin and Hokkaido islands are presented. The numerical simulation of the tsunami propagation in the Tatar Strait was performed. The results of the calculations are in satisfactory agreement with the observed data.

A mathematical model of unsteady flows of geofluids in mud volcanic processes

Mud volcanoes are widely spread throughout the world. They are located, for example, in Sakhalin, Krasnodar region, and Azerbaijan. In this work, we consider a mathematical model describing the motion and process of eruption of geofluids in a mud volcano. A method for obtaining unique solutions of the nonstationary inverse problem to determine the depth of the location of a volcano root and gas source was suggested for the first time on the basis of this model. The time period between two volcano eruptions and physicomechanical properties of geofluids, water-clayey breccia, and permeability of the supplying pipe are assumed known. Multidisciplinary investigations of mud volcanism allows us to estimate the possibility of existence of gas deposits and its resources in the given region as well as to study the dynamics of the fluid regime in the Earth’s crust. In addition, quantitative and qualitative analysis of the products and periodicities of mud volcano eruptions make it possible to study their influence on the ratio of greenhouse gases in the atmosphere. It is also important to determine the correlation between the seismicity and the manifestation of mud volcanism in a region. Few works exist on the construction of full models of mud volcanism. For example, the authors of [1] give an estimate of the gas source depth for a mud volcano based on the known solution for steady gas motion in a borehole. The authors of [2] present the supplying pipe of a mud volcano as a vertical cylindrical pipe, which is filled with a mud mixture moving in isothermal conditions. The solution of the direct problem is given on the basis of a system of compaction equations. The authors of [3] use a number of relations known from fluid and gas mechanics to estimate gas migration in mud volcano pipes. In this work we assume that mud volcanism is caused by the formation of tectonic fractures. According to the mechanism of descending filtration, a plug of water-clayey breccia is formed from the covering sedimentary layers in the region of fractures, which is supported from below by natural gas flowing from the gas source supplying the mud volcano. The supplying pipe of the volcano is considered a fissured porous medium filled with breccia and gas. In the course of time, unstable balance is established between the water-clayey plug and the gas, which is broken when the gas pressure increases and forces the breccia out. The depths of the location of the volcano root and gas source are determined from the condition of balance, thus we find the solution of the inverse problem. The process of forcing water-clayey breccia out by the gas is considered up to the moment of its eruption, when the gas pressure drops. Then, again the supplying pipe is filled, and the access to the deep gas in the pipe is stopped. Thus, a new eruption is being prepared. The gas that remained in the region of the mixture of breccia and gas would be released to the Earth’s surface through the system of gryphons of the mud volcano.

The Gornozavodsk earthquake of August 17(18), 2006, in the south of Sakhalin Island

The August 17 (18), 2006, Gornozavodsk earthquake (Mw = 5.6) in the southwestern part of Sakhalin was preceded by a number of anomalous seismological and geophysical phenomena. The extensive data recorded by a network of digital seismic stations make it possible to track the aftershock dynamics of the process within 24 hours after the main event. The paper describes various manifestations of the earthquake.

New data on the material composition of mud volcano products on Kerch Peninsula

The results of recent studies of the isotope and chemical composition of the waters and breccias that erupted from mud volcanoes of Kerch Peninsula are presented. It was found that the waters of the volcanoes considered were characterized by low salinity, a chloride–hydrocarbonate–sodium composition, and an increased 18O content. The breccias were enriched in organic matter and some microelements (Li, Se, Hg, etc.). As for petrogenic elements, depletion of Ca in the breccias is noted.

Modeling of the temperature regime of mud volcano gryphons

This paper is devoted to modeling of the dynamics of the temperature regime of mud volcano gryphons. The model is elaborated on the basis of a nonstationary equation of thermal conductivity with a convective component and describes well the observed regularities of thermal regime of South Sakhalin mud volcano gryphons. It is shown that anomalous changes in the temperature of the water-mud mixture after the Gornozavodsk and Nevelsk earthquakes in 2006–2007 are caused by variations in motion velocity of the mixture in the supply pipes of gryphons. It also has been shown that influx of deep geofluids cannot be considered as the main reason for thermal anomalies.

Change of Landscape Structure of Matua Island after the Sarichev Volcano Peak Eruption June 12-15, 2009

Due to the Sarichev volcano peak eruption June 12–15, 2009, the landscape of Matua Island was modified greatly. On the basis of field data, the spatial structure of the island landscape before and after eruption was analyzed. Scale maps 1: 200 000 reflecting the landscape structure of the island before June 12 and on June 30 are presented. It was established that the landscape on the slope of the volcano cone was essentially restructured by the influence of pyroclastic flows and volcanic ash fall-out. Complication of the island structure was noted after the volcanic eruption.

Relationship between variations in the rotation velocity of the Earth and its seismic activity

It is shown that, for the low-frequency component of the time series in the angular velocity of the Earth’s rotation, the maximums of seismic activity correspond to the final stages of decrease in the angular velocity of rotation (deceleration) and the local minimums coincide with maximums of seismic activity. The minimums of seismic activity correspond to the stages of increase in the angular velocity (acceleration).

Hydrodynamic instability at mid-latitudes of the earth caused by the rotation of the planet

641 For almost 100 years the scientific community has been trying to solve the intriguing problem of the “crit ical latitudes” [11]. According to the theoretical stud ies in the field of precession, nutation, and the exact form of the Earth, a stressed state of the planet exists in the zone of the 35th latitude (in the Northern and Southern hemispheres). In these zones (±35°) the main tensions lead to the formation of the deep frac ture system and folding in the crust layer [3, 4]. How ever, the problem about the reasons and physical mechanism that cause the fact that the critical lati tudes play a special role in the formation of the Earth’s topography and manifestation of the seismic activity remains open. The objective of this work is to present a model describing the development of two symmetric zones of hydrodynamic instability with respect to the equator and to show the manifestations of this insta bility on the basis of the recent geophysical observa tions. These zones are caused by the rotation of the planet. They are located at mid latitudes.

Unusual Eruption of the Main Pugachevo Gas-Water-Lithoclastic Volcano of Sakhalin in Winter 2005

Volcanologists are well aware of periodicity in the activity of virtually all present-day volcanoes: relatively short-term vigorous eruptions are separated by longer periods of relative calm or repose right up to complete cessation of any visible or perceptible activity. This scenario refers in full measure not only to genuine active volcanoes (gas‐lava‐pyroclastic), but also to so-called mud (gas‐water‐lithoclastic) volcanoes