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基于大陆岩石圈塑性流动网络和塑性流动波的观念，地震迁移主要表现为塑性流动波控制下地震沿网带的迁移。中东亚网络系统存在着两种以上的塑性流动波，其中与地震中期预测有关的是“十年波”和“百年波”。它们具有不同的起波年份、起波期和波峰带，而各期波的优势传播方向和有效作用范围又有所不同。两种波的波峰带相互叠合形成双重波峰区，其中有“塑性流动－地震”网带经过的区段为地震提供必要的能量背景条件，构成能量背景区。对中国大陆１９７６年震情的检验表明，６．０～７．８级地震共１９次，约有９０％分布在相应震级范围的能量背景区内 相似文献
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岩石圈下层的网状塑性流动 ,作为包含塑性流动网络的黏塑性流动 ,控制着大陆板块内部的构造变形和动力学过程。塑性流动网络由两组网带共轭相交而成 ,而塑性流动网带是黏塑性流动过程中因剪切局部化、黏性摩擦生热和网带介质的弱化而形成的延性弱面 (弱带 )。研究表明 ,类似于断裂和节理等脆性弱面 ,延性弱面对介质强度的影响也具有条件性 ,即当应力方向改变时 ,只有在滑移角θ不超出一定限值的条件 (θ1≤θ≤θ2 )下才可能沿原有弱面滑移 ,显示其弱化效应 ;延性弱面可以用弱化度R表示其屈服限的相对降低程度 ,弱化度与滑移角下限值之间的关系为R =sin2θ1;根据亚洲中东部地区“塑性流动 -地震”网络的最大共轭角推算 ,网带的弱化度R近似于 0 81。基于延性弱面效应的认识 ,文中就网带由剪切滑移向压性褶皱的转化、网带的继承与弃置以及应力方向的允许偏角等问题进行了探讨 相似文献
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本文报道了莺歌海盆地、北部湾盆地共148个新测热导率数据,根据收集的钻井温度数据新增计算65个大地热流数据;结合前人研究成果绘制了南海北部大陆边缘沉积盆地的地温梯度图、大地热流分布图;系统归纳了南海北部大陆边缘油气勘探成果.结果表明,南海北部大陆边缘珠江口盆地、琼东南盆地、北部湾盆地、莺歌海盆地的平均热流值分别为68.7±11 mW/m2、71.1±13 mW/m2、65.7±8.9 mW/m2、74.7±10 mW/m2,属于典型的“热盆”.热流区域分布特征总体上受大地构造背景控制,随地壳厚度从北向南,由陆架到陆坡区逐渐减薄而增高,水热活动与岩浆活动等是引起局部高热流异常的原因.盆地地温场的差异控制和约束了油气分布富集规律,从研究区油气勘探成果中可以发现,该区域的气田多发育于高热流盆地（凹陷）,而中-低热流盆地（凹陷）则多孕育油田,油气田具有“北油南气”的分布特征. 相似文献
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根据先前相似模型实验的结果 ,在板块边界驱动下 ,沿岩石圈下层 (含下地壳和岩石圈地幔 )传播的塑性流动波包括“快波”和“慢波” ,二者均属于黏性重力波 ,并分别由主波和辅波叠加而成。“快波”以 10 0 ～ 10 2 km/a量级的速度传播 ,已为塑性流动波控制下地震迁移的研究所证实。文中根据 7级以上强震的条带状分布图像 ,证明在喜马拉雅弧驱动下还存在着波速仅为 10 0 ～ 10 1m/a量级的“慢波” ,其中对 7级以上强震起控制作用的主要是“慢波”的辅波 ,其平均波长为 4 45km ,波速为 0 81～ 2 80m/a ,周期为 0 .16～ 0 .5 5Ma。“慢波”的边界起波时间距今约 1.34～ 4 .6 6Ma ,相当于上新世中期至早更新世中期 ,与喜马拉雅构造运动的主要活跃期 (幕 )之一相吻合。以喜马拉雅弧西段和东段为波源所形成的2个“慢波”系统的波峰带相互重叠 ,为 7级以上强震的发生提供了必要的能量背景 相似文献
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根据“网状塑性流动”大陆动力学模型,岩石圈的变形方式由浅层脆性向深层延性的转变以及岩石圈下层网状塑性流动的控制作用,导致板块内部的多层构造变形。GPS方法或断层错动反演方法所测定的只是浅表地壳。多震层的应变速率可用“地震复发间隔法”,根据先后两次地震的复发间隔和后发地震的发震概率予以估计。基于岩石圈下层塑性流动网络共轭角与挤压变形之间的关系,可运用“共轭角法”估计该层的应变,并结合对于变形时间的估计,进一步推算网络的特征应变速率。文中给出了亚洲中东部地区岩石圈下层特征应变速率的等值线图,其数量级为10-15～10-14/s。控制多震层地震活动的主要是塑性流动网带,其应变速率大于网络的特征应变速率,除此以外,多震层的应变速率还受到驱动边界的直接作用、塑性流动波和上下层之间非连续分布软弱层的影响。根据青藏高原至华北平原11个潜在震源区所在地段多震层应变速率与岩石圈下层特征应变速率的对比分析,除临汾盆地1处偏差较大外,其余10处两者间表现出显著的线性相关,其比值β平均为1.75,分布范围为1.25～2.25。文中建议在进行中长期地震预测时,可根据岩石圈下层特征应变速率等值线图,结合比值β的引入,粗略地估计各潜在震源 相似文献
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沉积盆地现今热流特征是岩石圈构造-热演化过程的综合反映和盆地热史恢复的必要约束条件,其总体变化趋势与热岩石圈厚度密切相关.本文根据新收集的珠江口盆地19口钻井温度数据,新增计算了19个大地热流数据,其中12个数据位于深水区（水深大于300 m）,丰富了该盆地深水区钻井地热数据.结合前人研究成果,绘制了该盆地的大地热流图,并分析了其热流分布特征.在此基础上通过求解一维热传导方程,计算得到36口井位处的热岩石圈厚度,量化了盆地大地热流与热岩石圈厚度间的关系.结果显示,珠江口盆地大地热流值介于24.2~121.0 mW·m-2,平均71.8±13.6 mW·m-2,新增盆地深水区钻井平均热流值高达84.5±4.4 mW·m-2.大地热流分布整体上从陆架区到陆坡区升高,而热岩石圈厚度整体分布趋势与大地热流相反.大地热流与热岩石圈厚度间存在良好的指数相关性. 相似文献
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根据中国南方地温梯度和大地热流的数据各418个,编制了中国南方地温梯度图和中国南方大地热流图,研究了中国南方现今地温梯度分布特征和大地热流分布特征.结果显示,中国南方地温梯度介于782～1625℃/km,平均241℃/km;大地热流变化于22～220 mW/m2之间,平均值为642 mW/m2.东南沿海和滇西南地区为高地温梯度分布区,扬子地块为中－低温地温梯度区.地温梯度不仅与区域热构造背景有关,还显著地受地下水热活动、断裂以及地层热导率影响.中国南方大地热流东部、西南部高,中部低,且异常高值点主要沿板块边界缝合带、深大断裂活动带分布.大地热流与区域构造运动、最后一次热事件发生的时间、岩石圈拉张程度、地壳厚度、壳内高导层埋深等因素具有明显的相关性. 相似文献
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Umberto Tomassetti Francesco Graziotti Luigi Sorrentino Andrea Penna 《地震工程与结构动力学》2019,48(11):1277-1296
The assessment of the out-of-plane response of masonry structures has been largely investigated in literature assuming that walls respond as rigid or semi-rigid bodies, and relevant equations of motion of single-degree-of-freedom and multi-degree of freedom systems have been proposed. Therein, energy dissipation has been usually modelled resorting to the classical hypotheses of impulsive dynamics, delivering a velocity-reduction coefficient of restitution applied at impact. In fewer works, a velocity-proportional damping force has been introduced, by means of a viscous coefficient being constant or variable. A review of such models is presented, a criterion for equivalence of dissipated energy is proposed, equations predicting equivalent viscous damping ratios are derived and compared with experimental responses. Finally, predictive equations are examined in terms of incremental dynamic analyses for large sets of natural ground motions. 相似文献
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Timothy Buscheck Douglas Mackay Charles Paradis Radomir Schmidt Nicholas de Sieyes 《Ground Water Monitoring & Remediation》2019,39(3):48-60
At a service station closed in 1993, groundwater contained benzene that persisted above the cleanup goal of 1 mg/L in zones depleted of background sulfate. The benzene and other petroleum hydrocarbons (PHCs) were present as much as 36 feet (11 m) below the water table and therefore remediation of a thick saturated zone interval was required. Microcosms using site sediments demonstrated that anaerobic benzene biodegradation occurred only if sulfate was added, suggesting sulfate addition as a remediation approach. Twenty-four boreholes (9.1″ diameter and 56′ deep) were drilled around four monitoring wells, in which benzene concentrations exceeded 1 mg/L. The boreholes were backfilled with a mixture of gravel and 15,000 pounds of gypsum (which releases sulfate as it dissolves) to create “Permeable Filled Borings” (PFBs). Concurrently, nine high pressure injections (HPIs) of gypsum slurry were conducted in other site locations (312 pounds of gypsum total). PFBs were expected to release sulfate for up to 20 years, whereas HPIs were expected to produce a short-lived plume of sulfate. Concentrations of benzene and sulfate in groundwater were monitored over a 3-year period in six monitoring wells. In two wells near PFBs, benzene concentrations dropped below the cleanup goal by two to three orders of magnitude; in one well, sulfate concentrations exceeded 500 mg/L for the most recent 18 months. Benzene concentrations in two other PFB monitoring wells declined by a factor of 2 to 4, but remained above 1 mg/L, presumably due to high-dissolved PHC concentrations and possibly greater residual PHC mass in adjacent sediments, and therefore greater sulfate demand. However, hydrogen and sulfur isotopic enrichment in benzene and sulfate, respectively, confirmed biodegradation of benzene and stimulation of sulfate-reducing conditions. Thus, it is hypothesized that the PHC mass in adjacent sediments will decline over time, as will dissolved PHC concentrations, and eventually benzene concentrations will decrease below the cleanup goal. Benzene in two HPI monitoring wells was below the cleanup goal for all but one sampling event before HPIs were conducted and remained below the cleanup goal after HPIs; there was no stimulation of sulfate-reducing conditions. It is concluded that sulfate released from PFBs contributed to declining benzene concentrations. 相似文献
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S. K. Kao 《Pure and Applied Geophysics》1980,119(1):9-15
In this paper, the Lagrangian equations of motion, thermodynamics, continuity and diffusion of a rotating, compressible, viscous atmosphere are derived. It is shown that the pressure force and Laplacian terms involving velocity, temperature and concentration in the Eulerian system become nonlinear in the Lagrangian system. In the case that these Laplacian terms can be neglected, the governing equations in the Lagrangian system can be greatly simplified, and particle dynamics and dispersion can be investigated. 相似文献
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PD Dr. Kolumban Hutter 《Aquatic Sciences - Research Across Boundaries》1983,45(1):101-144
Density distribution and temperature and current data which were measured in Lake of Zürich and Lake of Lugano in two summer field programs are scrutinized and interpreted by means of hydrodynamic models. Barotropic surface seiches and baroclinic internal seiches are studied using a one-and two-layer model and measured data permit identification of the respective resonant periods. Wind induced barotropic and baroclinic circulation dynamics is also studied by means of three-dimensional finite difference models of the hydrodynamic viscous equations on the rotating earth. In general the predictions of these models agree favorably with observed data. 相似文献
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For a high-velocity stable flow through a periodic corrugated channel representing an element of porous medium, we suggest splitting the overall nonlinear macroscopic effects into two kinds of different physical origin: a pure inertia effect produced by the convective term of Navier–Stokes equations and an inertia–viscous cross effect representing a variation of the viscous dissipation due to a streamline deformation by inertia forces. We will show that the inertia–viscous cross effects may be revealed by simulating a periodic flow, whilst the pure inertia effects are produced by the microscale flow nonperiodicity. We will reveal the individual flow law for each nonlinear component and analyze the relative role of both components numerically by using the finite element method applied to the Navier–Stokes equations. Both the pure inertia and the inertia–viscous cross effects are revealed to be exponential prior to quadratic or cubic ones. The influence of the dead volume is analyzed. The inertia–viscous cross phenomena are shown to be negligible when the flow structure is clearly nonperiodic. 相似文献
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本文在小扰动条件下,从粘性可压缩流体的运动方程、状态方程以及连续性方程导出了它的波动方程,从而表明粘性可压缩流体中能够存在有耗损的纵波与横波。文中还针对自由界面、刚性界面、粘性流体内部分界面、粘性流体与弹性固体分界面等,求出了平面波的反射系数和透射系数。 相似文献
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The numerical model of convection in magma sills is developed. The model is based on a full system of equations of fluid dynamics and includes heat transfer, buoyancy effects and diffusion of some minor component (marker). Solidification is treated as a phase transition. The results indicate that there are some qualitative differences between very thin sills with Rayleigh number Ra = 105 and thin sills with Ra = 106. For a basaltic magma the first case corresponds to the thickness of the sills of approximately 30 cm and the second case corresponds to the thickness of 60 cm. In the first case mixing is inefficient and conduction is the dominant form of heat transfer. In the second case mixing is efficient and convection is the dominant form of heat transfer. Some of the results can be scaled for the more viscous magmas in thicker sills. 相似文献
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Beatriz Quintal Eva Caspari Klaus Holliger Holger Steeb 《Geophysical Prospecting》2019,67(8):2196-2212
In interconnected microcracks, or in microcracks connected to spherical pores, the deformation associated with the passage of mechanical waves can induce fluid flow parallel to the crack walls, which is known as squirt flow. This phenomenon can also occur at larger scales in hydraulically interconnected mesoscopic cracks or fractures. The associated viscous friction causes the waves to experience attenuation and velocity dispersion. We present a simple hydromechanical numerical scheme, based on the interface-coupled Lamé–Navier and Navier–Stokes equations, to simulate squirt flow in the frequency domain. The linearized, quasi-static Navier–Stokes equations describe the laminar flow of a compressible viscous fluid in conduits embedded in a linear elastic solid background described by the quasi-static Lamé–Navier equations. Assuming that the heterogeneous model behaves effectively like a homogeneous viscoelastic medium at a larger spatial scale, the resulting attenuation and stiffness modulus dispersion are computed from spatial averages of the complex-valued, frequency-dependent stress and strain fields. An energy-based approach is implemented to calculate the local contributions to attenuation that, when integrated over the entire model, yield results that are identical to those based on the viscoelastic assumption. In addition to thus validating this assumption, the energy-based approach allows for analyses of the spatial dissipation patterns in squirt flow models. We perform simulations for a series of numerical models to illustrate the viability and versatility of the proposed method. For a 3D model consisting of a spherical crack embedded in a solid background, the characteristic frequency of the resulting P-wave attenuation agrees with that of a corresponding analytical solution, indicating that the dissipative viscous flow problem is appropriately handled in our numerical solution of the linearized, quasi-static Navier–Stokes equations. For 2D models containing either interconnected cracks or cracks connected to a circular pore, the results are compared with those based on Biot's poroelastic equations of consolidation, which are solved through an equivalent approach. Overall, our numerical simulations and the associated analyses demonstrate the suitability of the coupled Lamé–Navier and Navier–Stokes equations and of Biot's equations for quantifying attenuation and dispersion for a range of squirt flow scenarios. These analyses also allow for delineating numerical and physical limitations associated with each set of equations. 相似文献