Vol 53, No 6 (2017)

The most general approach to studying the recurrence law in the area of the rare largest events is associated with the use of limit law theorems of the theory of extreme values. In this paper, we use the Generalized Pareto Distribution (GPD). The unknown GPD parameters are typically determined by the method of maximal likelihood (ML). However, the ML estimation is only optimal for the case of fairly large samples (>200–300), whereas in many practical important cases, there are only dozens of large events. It is shown that in the case of a small number of events, the highest accuracy in the case of using the GPD is provided by the method of quantiles (MQs). In order to illustrate the obtained methodical results, we have formed the compiled data sets characterizing the tails of the distributions for typical subduction zones, regions of intracontinental seismicity, and for the zones of midoceanic (MO) ridges. This approach paves the way for designing a new method for seismic risk assessment. Here, instead of the unstable characteristics—the uppermost possible magnitude M_max—it is recommended to use the quantiles of the distribution of random maxima for a future time interval. The results of calculating such quantiles are presented.

The comparative analysis of the Earth’s surface deformations measured by ground-based and satellite geodetic methods on the regional and zonal measurement scales is carried out. The displacement velocities and strain rates are compared in the active regions such as Turkmenian–Iranian zone of interaction of the Arabian and Eurasian lithospheric plates and the Kamchatka segment of the subduction of the Pacific Plate beneath the Okotsk Plate. The comparison yields a paradoxical result. With the qualitatively identical kinematics of the motion, the quantitative characteristics of the displacement velocities and rates of strain revealed by the observations using the global navigational satellite system (GNSS) are by 1–2 orders of magnitude higher than those estimated by the more accurate methods of ground-based geodesy. For resolving the revealed paradoxes, it is required to set up special studies on the joint analysis of ground-based and satellite geodetic data from the combined observation sites.

The results of laboratory experiments on studying the electrical conductivity σ of a clay mineral montmorillonite from different sedimentary mineral deposits of Dagestan in the temperature interval from 100 to 1000°C are presented. The general regularities in the dependence of the electrical conductivity σ of the studied samples on the absolute temperature T are accounted for by the existence of the associated complexes of elementary defects of the crystal lattice. These complexes play important role in a variety of kinetic processes under the conditions of the Earth’s interior, and their existence is demonstrated by the experiments. The activation energy of the electrical conductivity and the preexponential factors are determined for all the temperature zones. The relationship between the pattern of temperature variations in electrical conductivity and the processes of releasing interlayer water and hydroxyls from different energy sites is established. It is concluded that the anomalous change in electrical conductivity in some samples reflects the postsedimentation changes of montmorillonite manifesting themselves by the emergence of a hydromuscovite component.

By monitoring the variations in the subsoil radon concentration in one of the geodynamically active zones of the Moscow syneclise, the effects are detected of changes in the stress-strain state of the Earth’s crust which predetermined the development of the processes that caused the deep-focus earthquake in the Sea of Okhotsk on May 24, 2013. The joint analysis of subsoil radon variations and neutrino flow variations measured in the same structural–geodynamical conditions support the previous data on the global character of the processes contributing to the preparation of strong and catastrophic earthquakes.

Typical publications concerning the study of geomagnetic excursions in the interval of the Brunhes chron are analyzed. The prolonged controversy on the number, age limits, and possibilities of using the geological sections for chronostratigraphic correlation is noted. The objective and subjective causes of this controversy are revealed, and a program of studies aimed at resolving the disagreements is suggested.

A hydromagnetic dynamo is only possible at a sufficiently powerful convection. In the Earth’s core, it is probably the nonthermal convection very much in excess of its critical level with the molecular transporr coefficients. However, in the case of medium- or large-scale fields, the critical energy level caused by the turbulent tranport coefficients is likely to be slightly below the actual level. This probably explains both the 22-year success of this type of simplified geodynamo models and the energy scaling laws for hydromagnetic fields, which generalize these models. Also the review of energy-dependent analytical and observational estimates of vortex fields, hydromagnetic scale sizes, and velocities in the core is presented. These typical parameters are partly in a new way linked to the observed and more ancient magnetic variations. New, albeit, simplified and self-evident, substantiation is given to the paleomagnetic hypothesis about the predominance of the axial dipole under a certain time averaging. In (Pozzo et al., 2012) and more recent works, it is shown that the adiabatic heat flow and electrical conductivity in the Earth’s core are severalfold higher than the generally accepted estimates. Here, the dynamo supporting Braginsky’s convection (Braginsky, 1963) (under the crystallization of the heavy fraction of a liquid onto the solid core) started less than 1 Ga ago, whereas the more ancient geodynamo was supported by the compositional convection of another type. The known mechanisms implementing this convection, which differ by the scenarios of magnetic evolution, are reviewed. This may help identify the sought mechanism through the most ancient paleomagnetic estimates of the field’s intensity and through the numerical models. The probable mechanisms of generation and their absence for the primordial and recent magnetic field of the studied terrestrial planets are discussed.