Two simple methods for the determination of the resonance frequencies of magnetic field lines

It has previously been shown that application of the “gradient method” to simultaneous recordings of geomagnetic pulsation fields at two stations on a meridian can determine the resonant frequency of a magnetic field line, and that the distribution of resonant frequencies along the meridian can be calculated from three stations. It is shown here that if the D-component spectrum of the pulsations is taken to be a representation of the driving wave, the same information can be derived from one and two station measurements, respectively, albeit with some slight loss of accuracy. It is also suggested that the empirical method of inferring the intensity of the interplanetary magnetic field from the measurement of the period of ground magnetic pulsations would be more accurate if D-component observations only were used.     

Experimental Studies of the Dynamic Interaction between Model Channel Forms and Flow

Interaction between water flow and ridge bedforms has been studied. The results of experimental studies of velocity distribution over ridge bedforms in a hydraulic laboratory flume are given. The distribution of pressure along the contour of a rigid model ridge, determined in an aerodynamic canal, is also given.     

Properties of fine technogenic sediments and their effect on channel process and self-purification of river water

The role of fine sediments of technogenic origin in channel process is analyzed. The specific features of sedimentation of particles with different density and shape and the issues of flocculation and consolidation of sediments in the bottom part of flow are discussed. Experimental data on the adhesion of particles are given and a relationship for its assessment is proposed. The class of sediments for which the adhesion determines the critical erosion velocity is determined. The processes of river water self-purification and precipitation of fine sediments were compared to show that sedimentation processes play an important role in river water self-purification.     

A Stochastic Two-node Stress Transfer Model Reproducing Omori's Law

— We present an alternative to the epidemic type aftershock sequence (ETAS) model of Ogata (1988). The continuous time two-node network stress release/transfer Markov model is able to reproduce the (modified) Omori law for aftershock frequencies. One node (denoted by A) is loaded by external tectonic forces at a constant rate, with `events' (main shocks) occurring at random instances with risk given by a function of the `stress level' at the node. Each event is a random (negative) jump of the stress level, and adds (or removes) a random amount of stress to the second node (B), which experiences `events' in a similar way, but with another risk function (of the stress level at that node only). When that risk function satisfies certain simple conditions (it may, in particular, be exponential), the frequency of jumps (aftershocks) at node B, in the absence of any new events at node A, follows Omori's law \((\prpto (c + t)^{-1})\) for aftershock squences. When node B is allowed tectonic input, which may be negative, i.e., aseismic slip, the frequency of events takes on a decay form that parallels the constitutive law derived by Dieterich (1994), which fits very well to the modified Omori law. We illustrate the model by fitting it to aftershock data from California post-1973, and from the Valparaiso earthquake of March 3 1985.     

Depleted and enriched matter in the upper mantle of Spitsbergen: Evidence from the study of mantle xenoliths

Doklady Earth Sciences -     

Reconstruction of the Neoproterozoic–Cambrian Orogenesis in Princess Elisabeth Land (East Antarctica) from a Study of Granitic Rocks

Abundant Cambrian granitic rocks in Princess Elizabeth Land and adjacent regions of Antarctica occupy various positions (from syn- to postkinematic) in the structure of the crust. Their mineral and isotopic composition reflects both the character and age of the parental substrate and geodynamic formation conditions of the region. The study of Cambrian processes is important for this region, because almost all known models of the formation of the Gondwana supercontinent suggest the Neoproterozoic–Cambrian amalgamation of two or three continental blocks, parts of which can be distinguished in this sector. The paper presents geological data on granitic rocks, as well as their mineral and Nd isotopic composition. Field observations and analytical data indicate a different structure and petrographic composition of Cambrian granitic rocks in Princess Elizabeth Land, which are related to their different formation conditions. Synkinematic biotite or garnet–biotite peraluminous S-type granites mostly occur in the eastern Princess Elizabeth Land. Mostly late and postkinematic biotite and amphibole–biotite (±orthopyroxene) granites or granodiorites are typical of its western part. Their compositions are similar to that of A-type granites. In comparison with coeval granites in adjacent areas, the character of Cambrian granites in Princess Elizabeth Land substantiates the presence of structural zones identified from geological data and indicates the presence of a Cambrian orogen probably with a collisional nature, as well as the location of its hinterland in intracontinental Antarctica.     

Analysis of the Impact of Hydrotechnical Construction on the Amur River near Blagoveshchensk and Heihe Cities Using a Two-Dimensional Hydrodynamic Model

Water flow and sediment transport under the effect of hydrotechnical constructions on the Amur River near Blagoveshchensk and Heihe cities was analyzed based on two-dimensional hydrodynamic modeling using STREAM_2D software (the authors V. Belikov et al., Russia). Three modeling scenarios were considered: without constructions, with the embankment of Blagoveshchensk, with the embankment of Blagoveshchensk and a system of dams near the Chinese island of Big Heihe. Modeling results have shown that the embankment has only a local effect on the part of the Amur R. upstream from confluence with the Zeya R. The construction of dams in the side channels near the island of Big Heihe can lead to significant flow redistribution, providing the flow concentration in the main river channel and reduction of the water flow, entering the island system. An increase in erosion in the main channel downstream of the confluence near the left bank and a simultaneous increase in accumulation near the right bank of the Amur R. below the island system can take place as the result of side channels shutting by dams from the right bank.     

High resolution method of direct measurement of the magnetic field lines'' eigen frequencies

The simultaneous observations of Pc4 geomagnetic pulsations at the two temporary stations, located along the geomagnetic meridian 50 km to the North and South from the observatory Borok (L = 2.8), have been used for the investigation of amplitude gradients of both H- and D-components of these pulsations. It has been discovered that the direction of a meridional component of the gradient H (grad_MH) depends on the frequency ƒ of a spectral component of pulsations. The grad_MD is directed more or less permanently northward independently from the frequency ƒ These results are the consequence of a local amplification of geomagnetic pulsations due to Alfvén waves resonance along the magnetic field lines. It has been demonstrated that the frequencies ƒ_R for which the northward direction of grad_MH is replaced by the southward one (with increasing ƒ) can be interpreted as the eigen frequencies of the field line which intersects the meridian in the middle between two temporary stations, i.e. in Borok.

The possible applications of a gradient method of measurement of the magnetic field lines' eigen frequencies are discussed.