Dynamics of interaction between fields of seismicity and surface deformations (Bishkek geodynamic test area)   总被引：1，自引：0，他引：1  

G. A. Sobolev  N. A. Zakrzhevskaya  K. N. Akatova  V. G. Gitis  A. B. Derendyaev  V. D. Bragin  N. A. Sycheva  S. I. Kuzikov 《Izvestiya Physics of the Solid Earth》2010,46(10):817-838

The spatial-temporal dynamics of surface crustal movements revealed from GPS data is compared with seismicity in the Bishkek geodynamic test area documented in the regional KNET catalog. The geological information system (GIS) GeoTaim 2.0 is substantially improved, which allowed variations in seismicity and deformation fields to be analyzed in the 3D raster. It is shown that seismicity and surface deformations are correlative in the test area. The periods with extreme values of contraction and the extension rates of the Earth’s surface areas are accompanied by enhanced seismicity and strong earthquakes. The increase in the spatial gradient of surface crustal movements coincides with changes in the azimuths of compression axes indicated by mechanisms of earthquakes that occurred at depths of up to 25 km. For a better geological—geophysical interpretation of interactions between deformation and seismicity fields in the Bishkek geodynamic test area, the spatial system GPS stations and measurement frequency need substantial improvement.  相似文献   

Quasi-stationary striations in basin-scale oceanic circulation: vorticity balance from observations and eddy-resolving model     

Oleg V. Melnichenko  Nikolai A. Maximenko  Niklas Schneider  Hideharu Sasaki 《Ocean Dynamics》2010,60(3):653-666

Recently, prominent jet-like features of the ocean circulation, called striations, with a meridional scale of O(300–500 ;km) and extending for thousands of kilometers in length, have been detected in satellite and in situ observations and in high-resolution numerical models. In this paper, we study quasi-stationary striations, which are best seen in the multi-year time-averaged velocity fields. Using 1993–2002 mean dynamic ocean topography, satellite altimeter observations, and output of the Ocean General Circulation Model for the Earth Simulator, the dynamics of the quasi-stationary striations in the eastern parts of the subtropical North and South Pacific are examined by assessing individual terms in the time-averaged equations of relative and potential vorticity. While non-linear effects are found to be essential in the dynamics of the striations, rejecting some linear hypotheses forwarded in the earlier studies, the relevance of the Rhines mechanism is not confirmed. Eddy flux does not act as a relative vorticity source for the striations. Using the potential vorticity (PV) diagnostics, we show that the time-mean PV is not conserved along the time-mean streamlines, and on the scale of the striations these changes in PV are largely induced by the eddy flux of layer thickness. The fact that eddy fluxes contribute to the striations’ time-mean PV budget suggests that the striations are not a kinematical artifact of time-averaging of westward-propagating eddies.  相似文献   

Initiation of unstable slips–microearthquakes by elastic impulses     

G. A. Sobolev  A. V. Ponomarev  Yu. Ya. Maibuk 《Izvestiya Physics of the Solid Earth》2016,52(5):674-691

A series of laboratory experiments have been carried out with a model of two granite blocks under biaxial compression loading. The experiments are mainly intended for assessing the possibilities of partially releasing the accumulated potential energy. The model was subjected to calibrated mechanical impacts (strokes) which induced elastic impulses. The mechanical stresses, strains, and acoustic emission were recorded. The strokes caused both large slips releasing the stresses down to their initial level and small slips which reduced the stresses by 5–8%. The small slips mostly occurred after the precursory emergence of the low frequency oscillations having low amplitudes. Before the large slips, the stages of speeding-up of the relative motion of the sides of the block contact was observed, similar to those emerging before the natural slips unrelated to the strokes. This feature was not universal: in some cases, the model recovered to the stationary state of the block contact without a large slip. All the slips occurred with a time delay after the stroke. The time delay was shorter when the energy of the blow was higher. With the shorter time delays, the small slip is more likely to occur. The energy of the impacts was by three orders of magnitude lower than the energy accumulated by the model, which points to the triggering mechanism of slip initiation. The series of strokes resulting in the small displacements partially reduced the accumulated energy and prevented the emergence of large motions such as the stick-slip events. If after a series of such blows a large sliding event still occurred, its energy was higher than in the slips unrelated to the impacts. The experiments revealed the difficulties in solving the problem of earthquake hazard reduction by elastic impacts.  相似文献   

Preface: Contribution of Vladimir S. Sobolev to the study of petrology of the lithosphere and diamond genesis     

N.V. Sobolev 《Russian Geology and Geophysics》2009,50(12):995-998

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Editorial     

N.V. Sobolev 《Russian Geology and Geophysics》2009,50(5):395

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Pyrope–knorringite garnets: overview of experimental data and natural parageneses     

A.I. Turkin  N.V. Sobolev 《Russian Geology and Geophysics》2009,50(12):1169-1182

This paper gives an analytical overview of the experimental data obtained by different authors at high P and T in the model system MgO–Al₂O₃–SiO₂–Cr₂O₃ (MASCr). A set of four simple polynomial equations is proposed for the temperature and pressure dependence of chromium content in garnet and spinel in the assemblage Gar + Opx + Es and Gar + Fo + Opx + Sp.From the first equation, one can estimate the minimum pressure at a given temperature which is required for the formation of peridotite garnets of uncertain paragenesis with a known knorringite content. A combination of the second and third equations helps estimate P and T from the chromium content of garnet and spinel from assemblages containing both minerals. If the spinel composition is unknown, but there is reason to assign garnet to a spinel-bearing paragenesis, the fourth equation is applicable for estimating pressure at given temperature.Originally, the proposed garnet–spinel geothermobarometer was developed for a harzburgite paragenesis. However, it is applicable to garnets with CaO/Cr₂O₃ < 0.903 (including lherzolitic ones), that is, those within the Pyr–Kn–Uv triangle of the reciprocal quaternary diagram Pyr–Cros–Uv–Kn.Using the above equations and an empirical P_CG geobarometer (Grütter et al., 2006), comparative geothermobarometric estimates were obtained for a set of garnet and garnet–spinel inclusions in diamonds and intergrowths with diamond, as well as garnet inclusions in spinel. If garnet has CaO/Cr₂O₃ = 0.35–0.40, the results are in good accord. For Cr-richest and Ca-poorest garnets, the P_CG barometer shows pressures 10–15% higher compared with our estimates.  相似文献   

Chemodynamical evolution of gas near an expanding HII region     

M. S. Kirsanova  D. S. Wiebe  A. M. Sobolev 《Astronomy Reports》2009,53(7):611-633

A self-consistent model for the chemical-dynamical evolution of a region of ionized hydrogen around a massive young star and of the surrounding molecular gas is presented. The model includes all main chemical and physical processes, namely the photoionization of atomic hydrogen, photodissociation of molecular hydrogen and other molecules, and the evaporation of molecules from the mantles of dust particles. Heating and cooling processes are taken into account in the temperature calculations, including cooling in molecular and atomic lines. The hydrodynamical equations were solved using the Zeus2D hydrodynamical software package. This model is used to analyze the expansion of a region of ionized hydrogen around massive stars (effective temperature of 30 000 and 40 000 K) in a medium with various initial density distributions. The competition between evaporation from dust mantles and the photodissociation of molecules results in the formation of a transition layer between the hot HII region and cool quiescent medium, characterized by high abundances of molecules in the gas phase. The thickness of the transition layer is different for different molecules. Since there is a velocity gradient along the transition layer, and the maxima in the distributions of different molecules are at different distances from the star, observations of molecular emission lines should reveal distinction in shifts of lines of different molecules relative to the velocity of the quiescent gas. Such shifts have indeed been detected during molecular observations of the region of ionized hydrogen Sh2-235. For an initial gas density of 10³ cm^?3, the increase in the abundances of H₂O and H₂CO in the transition layer after desorption from dust occurs gradually rather than in a jump-like fashion; therefore, the concept of a “evaporation front” can be used only formally. In addition, the distances between the evaporation fronts for different molecules are significant. At higher initial gas densities (10⁴ cm^?3), sharp evaporation fronts are formed for the different molecules, which are close to each other and to the shock front. In this case, it is possible to speak of a single evaporation front for CO, H₂O, and H₂CO.  相似文献   

Study of the surface of natural diamonds by the method of atomic force microscopy     

V. M. Sonin  A. A. Chepurov  D. V. Shcheglov  S. S. Kosolobov  A. M. Logvinova  A. I. Chepurov  A. V. Latyshev  N. V. Sobolev 《Doklady Earth Sciences》2012,447(2):1314-1316

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Introduction to a special issue of Izvestiya,Physics of the Solid Earth Journal     

G. A. Sobolev  V. S. Kuksenko  A. D. Zavyalov 《Izvestiya Physics of the Solid Earth》2011,47(10):857-858

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Effect of leaf litter degradation and seasonality on D/H isotope ratios of n-alkane biomarkers     

Michael Zech  Nikolai Pedentchouk  Katharina Leiber  Slobodan B. Markovi? 《Geochimica et cosmochimica acta》2011,75(17):4917-4928

During the last decade, compound-specific hydrogen isotope analysis of plant leaf-wax and sedimentary n-alkyl lipids has become a promising tool for paleohydrological reconstructions. However, with the exception of several previous studies, there is a lack of knowledge regarding possible effects of early diagenesis on the δD values of n-alkanes. We therefore investigated the n-alkane patterns and δD values of long-chain n-alkanes from three different C3 higher plant species (Acer pseudoplatanus L., Fagus sylvatica L. and Sorbus aucuparia L.) that have been degraded in a field leaf litterbag experiment for 27 months.We found that after an initial increase of long-chain n-alkane masses (up to ∼50%), decomposition took place with mean turnover times of 11.7 months. Intermittently, the masses of mid-chain n-alkanes increased significantly during periods of highest total mass losses. Furthermore, initially high odd-over-even predominances (OEP) declined and long-chain n-alkane ratios like n-C₃₁/C₂₇ and n-C₃₁/C₂₉ started to converge to the value of 1. While bulk leaf litter became systematically D-enriched especially during summer seasons (by ∼8‰ on average over 27 months), the δD values of long-chain n-alkanes reveal no systematic overall shifts, but seasonal variations of up to 25‰ (Fagus, n-C₂₇, average ∼13‰).Although a partly contribution by leaf-wax n-alkanes by throughfall cannot be excluded, these findings suggest that a microbial n-alkane pool sensitive to seasonal variations of soil water δD rapidly builds up. We propose a conceptual model based on an isotope mass balance calculation that accounts for the decomposition of plant-derived n-alkanes and the build-up of microbial n-alkanes. Model results are in good agreement with measured n-alkane δD results. Since microbial ‘contamination’ is not necessarily discernible from n-alkane concentration patterns alone, care may have to be taken not to over-interpret δD values of sedimentary n-alkanes. Furthermore, since leaf-water is generally D-enriched compared to soil and lake waters, soil and water microbial n-alkane pools may help explain why soil and sediment n-alkanes are D-depleted compared to leaves.  相似文献