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We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are shear deformation bands that developed under shallow burial conditions via strain hardening in dm-wide zones. The edges of the polygons are 1–5 m long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain <0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes. 相似文献
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Abstract This paper experimentally investigates the convective planform near critical in a fluid layer whose temperature-dependent viscosity varies from top to bottom by up to a factor of 1500. Convection occurs in three different planforms: rolls, hexagons and squares. The square planform, which appears only for fluids with viscosity variation greater than about 50, replaces the hexagonal convection pattern as the Rayleigh number increases much above critical. The large amplitude of hexagonal convection with strong viscosity variation precludes studying the hexagon-square transition with perturbation methods of the type used to study the hexagon-roll transitions at smaller viscosity variations. 相似文献
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本文阐述了空间大地网联合处理中的地壳运动模型的建立方法，并在此基础上提出了非均匀形变，均匀形变，体应变和刚体转动的识别方法，文中以我国现有空间大地网的模拟数据，结合中国大陆地壳构造进行了试算。 相似文献
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Abstract A model of a homogeneous isotropic turbulent flow is presented. The model provides different realizations of the random velocity field component with given correlation latitudinal and lateral functions and a spatial structure which obeys the Kolmogorov theory of homogeneous and isotropic turbulence. For the generation of the turbulent flow the structural function of the flow in the form suggested by Batchelor (Monin and Yaglom, 1975) was used. This function describes the spectrum of turbulence both in the viscous and inertial ranges. The isotropy and homogeneity of the velocity field of the model are demonstrated. The model is aimed at simulating the ‘‘fine'’ features of drop's (aerosol particles') motion, such as the deviations of drops’ velocity from the velocity of the flow, detailed structures of drops’ tracks, related to drops’ (particles') inertia. The model is intended also for the purpose of studying cloud drops’ and aerosol particles’ motion and their diffusional spreading utilizing the Monte Carlo methods. Some examples of drop tracks for drops of different size are presented. Drops’ tracks are very sophisticated, so that the relative position of drops falling initially from the same point can vary drastically. In some cases drops’ tracks diverge very quickly, in other cases all drops move within a turbulent eddy along nearly the same closed tracks, but with different speed. The concentration of drop tracks along isolated paths is found in spite of the existence of a large number of velocity harmonics. It is shown that drops (aerosol particles) tend to leave some areas of the turbulent flow apparently due to their inertia. These effects can possibly contribute to inhomogeneity of drops’ concentration in clouds at different spatial scales. 相似文献
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Growth of homogeneously nucleated water droplets: a quantitative comparison of experiment and theory
The formation of aerosols proceeds through nucleation, growth and aging stages. The understanding of nucleation and droplet growth is essential for handling the more complex atmospheric condensation processes. To achieve this goal, measurements of the nucleation rate of various systems are performed in an expansion chamber. In this manner nucleation and growth are decoupled by applying a short nucleation pulse of about 1 ms during which the nuclei are formed. The subsequent droplet growth is quantitatively monitored by Mie-scattering. To this end, the Mie-maxima and -minima are detected as a function of time and compared to theoretical Mie-scattering calculations for increasing radii. In this fashion, a wealth of growth curves for pure water depending on supersaturations, number densities of droplets, and temperatures were obtained. Following the approach of Fuchs and Sutugin [Fuchs, N.A., Sutugin, A.G., 1970. Highly Dispersed Aerosols. Ann Arbor Science Publishers, Ann Arbor; Fuchs, N.A., Sutugin, A.G., 1971. In: Hidy, G.M., Brock, J.R. (Eds.), International Reviews in Aerosol Physics and Chemistry: Topics in Current Aerosol Research (Part 2), Pergamon, New York, p. 1], we calculated theoretical growth curves taking into account the depletion of water vapor, the increase of droplet- and system-temperature, temperature-dependent functions of the diffusion coefficient, surface tension, liquid density and latent heat of condensation. The calculated growth curves and experimental data for 230, 240 and 250 K with number densities of droplets between 5×102 and 2×106 droplets/cm3 yield quantitative agreement between theory and experiment. This is remarkable in so far as the theory contains no adjustable parameters and assumes the sticking probability of the vapor molecules to be unity. Using a sticking probability smaller than 0.8 in the calculation leads to growth functions already outside the experimental error. 相似文献
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在吸收并修正部分前人工作的基础上，给出了电导率分块均匀的瞬变电磁25维有限单元法正演算法. 在该算法中，（1）采用在矩形网格中进一步三角细化的剖分方式，同时考虑到矩形单元中心节点的性质，求解线性方程组前用高斯消元法消除矩形网格中心节点上的待求未知量，这样一方面较准确地模拟出任意二维复杂地电断面，另一方面又大大地节省了计算量；（2） 采用计算二次场的算法，事先仅需获得电场和磁场沿地电构造走向方向两个分量的一次场，故而不但计算精度较高，而且不明显增加计算量. 最后，对几例典型模型进行正演，并与解析解对比，验证了本文方法的有效性. 相似文献
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Asymptotic theory for calculating deformations caused by dislocations buried in a spherical earth: geoid change 总被引：2，自引：0，他引：2
W. Sun 《Journal of Geodesy》2003,77(7-8):381-387
An asymptotic theory is presented for calculating co-seismic potential and geoid changes, as an approximation of the dislocation theory for a spherical Earth. This theory is given by a closed-form mathematical expression, so that it is mathematically simple and can be applied easily. Moreover, since the asymptotic theory includes sphericity and vertical structure effects, it is physically more reasonable than the flat-Earth theory. A comparison between results calculated by three dislocation theories (the flat-Earth theory, the theory for a spherical Earth and its asymptotic solution) shows that the true co-seismic geoid changes are approximated better by the asymptotic results than by those of a flat Earth. Numerical results indicate that the sphericity effect is obvious large, especially for a tensile source on a vertical fault plane.
AcknowledgementsThe author is grateful to Dr S. Okubo for his helpful suggestions and discussions. Comments by anonymous reviewers are also greatly acknowledged. This research was financially supported by JSPS research grants (C13640420) and Basic design and feasibility studies for the future missions for monitoring Earths environment. 相似文献
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This work is a continuation of Musuuza et al. [37] in which a stability criterion for density-driven flow in a saturated homogeneous medium was derived. The criterion predicted the stability of a system as a function of the density and viscosity contrasts, the magnitude of the flow velocity and the concentration gradients for flow aligned orthogonal to gravity. It could not accurately predict stability transition with increasing velocity, a failure we attributed to dispersion effects that were not included. Small-scale dispersion and molecular diffusion, the main stabilising mechanisms in homogeneous media can stabilise flow if the instability wavelengths are below a certain cutoff. The width of the mixing zone is also central in controlling the range of wavelengths that persist into fingers. We propose a method of quantifying the cutoff wavelength and the width of the mixing zone, which are incorporated into the earlier criterion as constituents of the dispersive part. The earlier criterion is reformulated in terms of the Rayleigh number and with the dispersive part added, we attempt to predict the number of fingers formed which is directly related to the physical stability of the system. The inclusion of the Rayleigh number and dispersion into a single stability criterion provides new insight in the way dispersion affects vertical flow systems. Stability numbers computed with the new criterion are in reasonable agreement with numerical simulations for a range of physical variables. The numerical computations are performed with the software package d3f, which uses the cell-centred finite volume and the implicit Euler methods for the spatial and temporal discretisations, respectively. The admission of the density and dispersivities as inputs into the criterion makes it usable in practical problems. 相似文献