The electromagnetic field produced by oscillations of a magnetized incompressible infinitely long cylinder

The oscillations of a magnetized incompressible cylinder with a uniform magnetic field along its axis and the resulting electromagnetic field are studied. Two types of characteristic oscillations, torsional and Alfvén, are found to exist in the linear approximation. In the case of an infinite cylinder with torsional oscillations, no electromagnetic field is generated. In the case of Alfvén oscillations, an electromagnetic field develops around the cylinder with a local flux density that falls off exponentially with radial distance from the axis of the cylinder and has a time average of zero. The results are interpreted physically.     

Determining the Double Couple Moment Tensor for Kamchatka Earthquakes from Regional Seismic Waveforms

Izvestiya, Physics of the Solid Earth - Abstract—The digital seismic network in Kamchatka deployed in 2006–2010 provided a fundamental possibility for calculating seismic moment tensor...     

Slope Failure Initiation by Seismic Loading from Different Sources

Izvestiya, Physics of the Solid Earth - Abstract—We present the results of laboratory studies of slope failure criteria by dynamic impulse loading in the range of peak ground velocities (PGV)...     

Algorithm for calculating synthetic seismograms in a layered half-space with application of matrix impedance

A new algorithm is proposed for calculating the complete synthetic seismograms from a point source in the form of the sum of a single force and a dipole with an arbitrary seismic moment tensor in a plane layered medium composed of homogenous elastic isotropic layers. Following the idea of (Alekseev and Mikhailenko, 1978), an artificial cylindrical boundary is introduced, on which the boundary conditions are specified. For this modified problem, the exact solution (in terms of the displacements and stresses on the horizontal plane areal element) in the frequency domain is derived and substantiated. The unknown depth-dependent coefficients form the motion-stress vector, whose components satisfy the known system of ordinary differential equations. This system is solved by the method that involves the matrix impedance and propagator for the vector of motion, as previously suggested by the author in (Pavlov, 2009). In relation to the initial problem, the reflections from the artificial boundary are noise, which, to a certain degree, can be suppressed by selecting a long enough distance to this boundary and owing to the presence of a purely imaginary addition to the frequency. The algorithm is not constrained by the thickness of the layers, is applicable for any frequency range, and is suitable for computing the static offset.     

New paleomagnetic data on the Anabar Uplift and the Uchur-Maya region and their implications for the paleogeography and geological correlation of the Riphean of the Siberian Platform

The results of paleomagnetic studies of the reference sections of the Riphean and Late Proterozoic intrusive bodies of two remote areas of the Siberian Platform are presented. Within the limits of the Uchur-Maya region the sedimentary rocks of the Gonam, Omakhta, Ennin and Konder formations were studied; and the Riphean sedimentary rocks of the Burdur and Kotuykan formations on the northern and western slopes of the Anabar Uplift and, also, the Late Proterozoic intrusive complexes, located in the basins of the Fomich, Magan, Dzhogdzho and Kotuykan Rivers were studied. The paleomagnetic poles obtained in the course of this work and the present-day geochronological data give grounds to assume that: (1) the accumulation of the Riphean of the Anabar Uplift occurred after the formation of the Uchurskaya series of the Uchur-Maya region and was completed in approximately 1.5 Ga; (2) the Konder layers, compared according to the correlation pattern accepted at the present time [Semikhatov and Serebryakov, 1983] with the bottoms of the Totta formation, can be related to the appreciably more ancient stratigraphic level; (3) the intrusion of the studied intrusive bodies of the northern and western slopes of the Anabar Uplift occurred nonsimultaneously, although within close time intervals of approximately 1.5 Ga. The estimates of the kinematic parameters of the drift of the Siberian Platform within an interval of 1.7–1.0 Ga is carried out.     

Subduction of the Pacific plate under Kamchatka: Seismic velocity of underthrust

The results of studying the process of underthrusting in the Pacific plate under Kamchatka are presented, and the phenomena associated with this process are described. The seismic component of the velocity of the plate underthrust is estimated on the basis of (1) data from the CMT (Centroid Moment Tensor) catalog and (2) the sequence of the strongest Kamchatka earthquakes. A flat site with a strike azimuth of 217° and a dip angle of 25° located at depths of 30–70 km is assumed to be the interface between the plunging plate and Kamchatka. From CMT focal mechanisms, the underthrust velocity is estimated at V = 0.7 cm/yr for the southern zone (located south of Cape Shipunski) and at V = 1.1 cm/yr for the central zone (from Cape Shipunski to Cape Kronotski). From pairs of the strongest earthquakes that have occurred successively since 1737, the underthrust velocity for the southern zone is estimated at V = 6.6–7.1 cm/yr (from two pairs) and for the central zone, at V = 6.6 cm/yr. The creep portion of the underthrust amounts to 5–15% of the total velocity (the velocity of motion of the Pacific plate is 8 cm/yr).     

Some questions of geomechanics of the faults in the continental crust

We present the results of laboratory experiments on studying the formation of different slip modes on the interfaces in a rock massif such as aseismic creep, stick-slip, and periodic slow-slip events. It is shown that the way of releasing the accumulated elastic energy is determined by the mesoscale structure of the gouge rather than by its macroscopic strength characteristics. The evolution of the stress chains which are formed and broken during the displacement on the fracture, as well as the length and number of these chains, completely determines the regularities of the deformation. The role of these load-bearing elements in nature can be played, e.g., by the “contact spots,” which determine the regularities of stress concentration near the interblock boundary. We consider the effects of low-amplitude vibrations on stressed fractures. It is shown that, depending on the mode of deformation, the vibration impact can either reduce or boost the amplitude of separate events and the fraction of energy that is released dynamically. In the conclusion of the paper, we discuss the possibility of using the shear strength of the fault zone as a geomechanical parameter controlling the mode of deformation.     

Effect of solar radiation refraction on the zenith angle and times of the sunrise and sunset in the atmosphere

The analytical formulas for the solar radiation refraction angle and the times of the sunrise and sunset at altitudes of the atmosphere, which make it possible to take into account the dependence of these parameters on the temperature, density, and temperature vertical gradient in the atmosphere specified at the ground level, have been obtained. It has been indicated that solar radiation refraction pronouncedly affects the times of the sunrise and sunset at altitudes of the atmosphere.     

The main fault zone of East Sayan

Based on the structural and tectonophysical studies of the East Sayan fault zone (the stress fields determined from the slipping planes; and strain fields from dykes), we were able to describe more definitely the character of this regional fault. The right-lateral strike-slip on the rupture at the main stages of its development is established.