Image-domain wavefield tomography for tilted transversely isotropic media     

Vladimir Li  Ilya Tsvankin  Antoine Guitton  Hui Wang 《Geophysical Prospecting》2019,67(9):2358-2367

Transversely isotropic models with a tilted symmetry axis have become standard for imaging beneath dipping shale formations and in active tectonic areas. Here, we develop a methodology of wave-equation-based image-domain tomography for acoustic tilted transversely isotropic media. We obtain the gradients of the objective function using an integral wave-equation operator based on a separable dispersion relation that takes the symmetry-axis tilt into account. In contrast to the more conventional differential solutions, the integral operator produces only the P-wavefield without shear-wave artefacts, which facilitates both imaging and velocity analysis. The model is parameterized by the P-wave zero-dip normal-moveout velocity, the Thomsen parameter δ, anellipticity coefficient η and the symmetry-axis tilt θ. Assuming that the symmetry axis is orthogonal to reflectors, we study the influence of parameter errors on energy focusing in extended (space-lag) common-image gathers. Distortions in the anellipticity coefficient η introduce weak linear defocusing regardless of reflector dip, whereas δ influences both the energy focusing and depth scale of the migrated section. These results, which are consistent with the properties of the P-wave time-domain reflection moveout in tilted transversely isotropic media, provide important insights for implementation of velocity model-building in the image-domain. Then the algorithm is tested on a modified anticline section of the BP 2007 benchmark model.  相似文献   

Seismicityof the Novaya Zemlya archipelago: relocated event catalog from 1974 to 2014   总被引：1，自引：1，他引：0  

Alexey N. Morozov  Vladimir E. Asming  Natalya V. Vaganova  Yana V. Konechnaya  Yana A. Mikhaylova  Zinaida A. Evtyugina 《Journal of Seismology》2017,21(6):1439-1466

We have relocated seismic events registered in the area of the Novaya Zemlya Archipelago, which are not identified as nuclear explosions but are probably of tectonic nature. For the relocation, we collected all available seismic bulletins and waveform data. The location was performed by applying a modified method of generalized beamforming. Verification of the modified method and selection of the travel time model were performed using data on two Novaya Zemlya nuclear explosions that occurred on 02.11.1974 and 24.10.1990. The modified method and the BARENTS travel time model provide sufficient accuracy for event location in the region. The relocation procedure was applied for 9 seismic events registered in the area of the Novaya Zemlya Archipelago. As a result, the new coordinates of the five events turned out to be significantly different from those that were defined previously.  相似文献   

Role of the Rossiter-McLaughlin effect in the study of close binaries     

Galina N.Dryomova  Vladimir V.Dryomov 《天文和天体物理学研究(英文版)》2019,(3):21-30

This paper is devoted to binary stars belonging to the class of eclipsing-variable systems.Photometric and spectroscopic analysis of eclipses allows us to determine geometric parameters of the orbit and physical characteristics of stellar components as well as inclinations of stellar equators to the orbital plane. Estimations of inclinations can be obtained from measurement of the Rossiter-McLaughlin effect, which is discussed using examples of some eccentric binaries with an anomalous apsidal effect. Our task is to find the complete spectrum of solutions of the equation of apsidal motion, depending on the inclinations of the polar axes of the components to the orbital one for these systems, based on their individual spectroscopic and photometric observational data. The matrix of solutions allows us to select those pairs of polar inclinations that provide agreement with the observational apsidal period.  相似文献   

On the radiative and thermodynamic properties of the cosmic radiations using COBE FIRAS instrument data: IV. Sunyaev-Zel’dovich ($\mu$-type) distortion effect     

Anatoliy I. Fisenko  Vladimir F. Lemberg 《Astrophysics and Space Science》2018,363(11):224

The Sunyaev-Zel’dovich (SZ) effect represents a small spectral distortion to the cosmic microwave background (CMB) radiation, caused by the Compton scattering of CMB photons by the hot gas of galaxy clusters. In an early stage of universe, the SZ effect generates \(\mu\)-type of distortions for the CMB spectrum. A \(\mu\)-type distortion is created between the double Compton scattering decoupling (\(z \sim 10^{6}\)) and the thermalization decoupling by the Compton scattering (\(z \sim 10^{5}\)). In this case, to describe the small spectral distortion of the CMB spectrum, we use the Bose-Einstein (\(\mu\)-type) distribution with a non-zero chemical potential. At present, it is interesting to investigate the effect of this spectral distortion on the integral characteristics of the Bose-Einstein (\(\mu\)-type) spectrum. The thermal radiative and thermodynamic functions are such integral characteristics. These functions are as follows: a) the total radiation power per unit area; b) total energy density; c) number density of photons; d) grand potential density; e) Helmholtz free energy density; f) entropy density; g) heat capacity at constant volume; h) enthalpy density; and i) pressure. Precise analytical expressions are obtained for the temperature dependences of these functions. Using the observational data obtained by the COBE FIRAS, PIXIE, PRISM, and Planck missions, the thermal radiative and thermodynamic functions are calculated. A comparative analysis of the results obtained with the results for the same functions of the CMB spectrum at \(T = 2.72548~\mbox{K}\) is carried out. Very small distortions are observed for the thermal radiative and thermodynamic functions. In the redshift range \(10^{5} < z < 3 \times10^{6}\), these functions are calculated. The expressions are obtained for new astrophysical parameters, such as the entropy density/Boltzmann constant and number density, created by the Bose-Einstein (\(\mu\)-type) spectrum.  相似文献   

Ultramafic Zoned Complexes of the Urals and Siberia:New Geochemical Evidence of Magmatic Origin     

Vladimir SHMELEV  Maria CHERVYAKOVSKAYA 《《地质学报》英文版》2020,94(Z1):58-59

  相似文献   

Correction to: Zeolite containing rocks of kudurs and reasons of geophagy within the territory of Sikhote-Alin Nature Zapovednik,Far East of Russia     

Panichev  Aleksander  Seryodkin  Ivan  Popov  Vladimir  Chekryzhov  Igor  Makarevich  Raisa  Lutsenko  Tatiana  Stolyarova  Tatiana  Sergievich  Aleksander  Khoroshikh  Pavel  Maksimova  Darya  Petrunenko  Yury 《Arabian Journal of Geosciences》2020,13(4):1-11

This paper establishes a mechanical model of the stress distribution in front of the driving face during coal roadway excavation. Theoretical research shows that the stress state in the plastic zone of the driving face is consistent with the limit equilibrium equation, and the elastic zone is in accordance with the equilibrium equation based on elasticity mechanics. Based on this improved mechanical state solution model, different coal material constitutive hypotheses are used for the analysis. The width of the plastic zone calculated under the brittle-perfectly elastic model can reach 2–5 times the height of the roadway, and the stress concentration coefficient can reach two or more times. 3DEC numerical simulation software was used to simulate the stress distribution of the heading face. The results of the simulation are similar to those of the theoretical analysis. Compared with the elastic-perfectly plastic model, the calculated results of the brittle-perfectly elastic model are more consistent with the numerical simulation results. The heading face coal during roadway excavation shows obvious damage, and the strength characteristics of the coal decrease.  相似文献   

Clay-mineral and grain-size distributions in surface sediments of the White Sea (Arctic Ocean): indicators of sediment sources and transport processes   总被引：1，自引：1，他引：0  

Cornelia Saukel  Rüdiger Stein  Christoph Vogt  Vladimir P. Shevchenko 《Geo-Marine Letters》2010,30(6):605-616

In this study, the grain-size and clay-mineral compositions of 73 surface sediment samples collected in a variety of environmental settings in the White Sea are presented to characterize recent sedimentation processes, reconstruct transport pathways, and identify potential source areas of the terrigenous components. Areas >100 m deep are invariably characterized by silty clay, whereas areas <100 m deep exhibit more heterogeneous grain-size compositions plausibly explained by coastal erosion and (re-)distribution mechanisms, particularly tidal currents. The dominance of sand in the estuarine areas of the Onega and Dvina rivers as well as toward the Gorlo Strait connecting the White Sea with the Barents Sea is attributed to increased current speeds. Illite and smectite are the dominant clay minerals in recent sediments of the southwestern and eastern White Sea sectors, respectively. Their distribution patterns largely depend on the geology of the source areas, and mirror surface circulation patterns, especially in Dvina Bay. Smectite is a key clay mineral in White Sea surface sediments, as it reveals the dominating influence of the Northern Dvina’s runoff on sedimentation and water circulation throughout the basin. In comparison to other Eurasian shelf seas, the White Sea is characterized by a greater diversity of clay-mineral assemblages, which range from illite- to smectite-dominated sectors containing variable amounts of chlorite and kaolinite.  相似文献   

Borehole temperatures, climate change and the pre-observational surface air temperature mean: allowance for hydraulic conditions   总被引：1，自引：0，他引：1  

Louise Bodri  Vladimir Cermak 《Global and Planetary Change》2005,45(4):265-276

Joint analysis of surface air temperature series recorded at weather stations together with the inversion of the temperature-depth profiles logged in the near-by boreholes enables an estimate of the conditions existing prior to the beginning of the meteorological observation, the so-called pre-observational mean (POM) temperature.Such analysis is based on the presumption of pure diffusive conditions in the underground. However, in real cases a certain subsurface fluid movement cannot be excluded and the measured temperature logs may contain an advective component. The paper addresses the correction for the hydraulic conditions, which may have perturbed the climate signal penetrating from the surface into the underground. The method accounts for vertical conductive and vertical advective heat transport in a 1-D horizontally layered stratum and provides a simultaneous evaluation of the POM-temperature together with the estimate of the Darcy fluid velocity. The correction strategy is illustrated on a synthetic example and its use is demonstrated on temperature logs measured in four closely spaced boreholes drilled near Tachlovice (located about 15 km SW of Prague, Czech Republic). The results revealed that in a case of moderately advectively affected subsurface conditions (fluid velocities about 10⁻⁹ m/s), the difference between POM-values assessed for a pure conductive approach and for combined vertical conductive/advective approach may amount up to 0.3–0.5 K, the value comparable with the amount usually ascribed to the 20th century climate warming.  相似文献   

The cooling function of HD molecule revisited     

Anton Lipovka  Ramona Núñez-López  Vladimir Avila-Reese 《Monthly notices of the Royal Astronomical Society》2005,361(3):850-854

We report new calculations of the cooling rate of primordial gas by the HD molecule, taking into account its ro-vibrational structure. The HD cooling function is calculated including radiative and collisional transitions for   J ≤ 8  rotational levels, and for the vibrational levels v = 0, 1, 2 and 3. The ro-vibrational level population is calculated from the balance equation assuming steady state. The cooling function is evaluated in the ranges of the kinetic temperatures, T _k, from 10² to  2 × 10⁴ K  and the number densities, n _H, from 1 to  10⁸ cm⁻³  . We find that the inclusion of collisional ro-vibrational transitions increases significantly the HD cooling efficiency, in particular for high densities and temperatures. For   n _H≳ 10⁵  and   T _k∼ 10⁴ K  the cooling function becomes more than an order of magnitude higher than previously reported. We give also the HD cooling rate in the presence of the cosmic microwave radiation field for radiation temperatures of 30, 85 and 276 K (redshifts of 10, 30 and 100). The tabulated cooling functions are available at http://www.cifus.uson.mx/Personal_Pages/anton/DATA/HD_cooling/HD_cool.html . We discuss the relevance to explore the effects of including our results into models and simulations of galaxy formation, especially in the regime when gas cools down from temperatures above ∼3000 K.  相似文献   

Shipboard sunphotometer measurements of aerosol optical depth spectra and columnar water vapor during ACE‐2, and comparison with selected land, ship, aircraft, and satellite measurements     

John M. Livingston  Vladimir N. Kapustin  Beat Schmid  Philip B. Russell  Patricia K. Quinn  Timothy S. Bates  Philip A. Durkee  Peter J. Smith  Volker Freudenthaler  Matthias Wiegner  Dave S. Covert  Santiago Gassó  Dean Hegg  Donald R. Collins  Richard C. Flagan  John H. Seinfeld  Vito Vitale  Claudio Tomasi 《Tellus. Series B, Chemical and physical meteorology》2000,52(2):594-619

  相似文献