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1.
The inference of fault geometry from suprajacent fold shape relies on consistent and verified forward models of fault-cored folds, e.g. suites of models with differing fault boundary conditions demonstrate the range of possible folding. Results of kinematic (fault-parallel flow) and mechanical (boundary element method) models are compared to ascertain differences in the way the two methods simulate flexure associated with slip along flat-ramp-flat geometry. These differences are assessed by systematically altering fault parameters in each model and observing subsequent changes in the suprajacent fold shapes. Differences between the kinematic and mechanical fault-fold relationships highlight the differences between the methods. Additionally, a laboratory fold is simulated to determine which method might best predict fault parameters from fold shape. Although kinematic folds do not fully capture the three-dimensional nature of geologic folds, mechanical models have non-unique fold-fault relationships. Predicting fault geometry from fold shape is best accomplished by a combination of the two methods. 相似文献
2.
甘、宁、青地区地震孕育的力源环境 总被引:2,自引:0,他引:2
从3个方面讨论了甘、宁、青三省区地震孕育的力源环境。①从强震震源机制、地震形变带、断层滑移特征和现代形变、地应力实地测量等几个不同侧面,讨论了区域构适应力场的分布规律。指出,甘、宁、青现今区域构造应力场以水平为主,主压应力方向从地区的西部到东南部,由NNE逐渐转为近EW向,且在地壳的深部、浅部和地表,方向有较好的一致性。它是印度板块向青藏块体碰撞、挤压,使青藏块体向北东方向推济,同时向东蠕散的结果。②通过讨论发展断层的错动形式以及部分前兆资料所反映的应力特征,揭示了地震孕育过程中震源及周围地区处于一种更高的应力状态。这是该地区地震前兆具有普遍性的根本原因。③讨论了甘、宁、青现今地震的孕育方式。指出,6级以上地震基本上以先存断层重新活动或相互沟通为主要活动形式。 相似文献
3.
E. Tavarnelli 《International Journal of Earth Sciences》1996,85(2):363-371
The Umbria-Marche foreland fold-and-thrust belt in the northern Apennines of Italy provides excellent evidence to test the
hypothesis of synsedimentary-structural control on thrust ramp development. This orogenic belt consists of platform and pelagic
carbonates, Late Triassic to Miocene in age, whose deposition was controlled by significant synsedimentary extension. Normal
faulting, mainly active from Jurassic through Late Cretaceous-Paleogene time, resulted in significant lateral thickness variability
within the related stratigraphic sequences. By Late Miocene time the sedimentary cover was detached from the underlying basement
and was deformed by east-verging folds and west-dipping thrusts. Two restored balanced cross sections through the southernmost
part of the belt show a coincidence between the early synsedimentary normal faults and the late thrust fault ramps. These
evidences suggest that synsedimentary tectonic structures, such as faults and the related lithological lateral changes, can
be regarded as mechanically important controlling factors in the process of thrust ramp development during positive tectonic
inversion processes. 相似文献
4.
Application of an optimum design technique for determining the coefficient of consolidation by using piezocone test data 总被引:4,自引:0,他引:4
For normally consolidated clay, several researchers have developed a number of theoretical time factors to determine the coefficient of consolidation from piezocone test results. However, depending on assumptions and analytical techniques, it could vary considerably, even for a specific degree of consolidation. In this paper a method is proposed to determine a consistent coefficient of consolidation by applying the concept of an optimum design technique over all ranges of the degree of consolidation. Initial excess pore pressure distribution is assumed to be capable of being obtained by the successive spherical cavity expansion theory. The dissipation of pore pressure is simulated by means of a two-dimensional linear-uncoupled axi-symmetric consolidation analysis. The minimization of differences between measured and predicted excess pore pressure was carried out by the BFGS unconstrained optimum design algorithm with a one-dimensional golden section search technique. By analyzing numerical examples and in-situ test results, it was found that the adopted optimum design technique gives consistent and convergent results. 相似文献
5.
导水裂隙带高度预测途径探讨 总被引:3,自引:0,他引:3
导水裂隙带高度是设计防水煤(岩)柱尺寸的主要技术参数,是煤矿防治水工作的重要内容。详细论述了其研究现状及发展趋势,并提出了履岩体地质环境,履岩体力学环境和数值模拟技术三位一体的综合预测评价方法。 相似文献
6.
本文分析了三组结构面产状模型力学实验结果, 揭示了这种组合条件岩体中产生压剪区、张剪区及结构面、结构体的多种变形成分, 也揭示了压剪区和张剪区形成机理、及三组结构面组合下结构面产状的力学效应。 相似文献
7.
8.
Sealing layers are often represented by sedimentary sequences characterized by alternating strong and weak lithologies. When involved in faulting processes, these mechanically heterogeneous multilayers develop complex fault geometries. Here we investigate fault initiation and evolution within a mechanical multilayer by integrating field observations and rock deformation experiments. Faults initiate with a staircase trajectory that partially reflects the mechanical properties of the involved lithologies, as suggested by our deformation experiments. However, some faults initiating at low angles in calcite-rich layers (θi = 5°–20°) and at high angles in clay-rich layers (θi = 45°–86°) indicate the important role of structural inheritance at the onset of faulting. With increasing displacement, faults develop well-organized fault cores characterized by a marly, foliated matrix embedding fragments of limestone. The angles of fault reactivation, which concentrate between 30° and 60°, are consistent with the low friction coefficient measured during our experiments on marls (μs = 0.39), indicating that clay minerals exert a main control on fault mechanics. Moreover, our integrated analysis suggests that fracturing and faulting are the main mechanisms allowing fluid circulation within the low-permeability multilayer, and that its sealing integrity can be compromised only by the activity of larger faults cutting across its entire thickness. 相似文献
9.
介绍滇中红层形成的地质历史背景,红层分布范围,主要地层岩性及区内地质构造。重点讨论滇中红层特别是红层软岩的岩体原生结构,及后期受构造改造的岩体结构特性,岩体风化特性,岩体水理作用特性,岩体物理力学性质等四方面的工程地质特性。 相似文献
10.
Andrew G. Tomkins 《Mineralium Deposita》2007,42(6):627-637
The relative importance of mechanical re-mobilisation, hydrothermal dissolution and re-precipitation, and sulphide melting
in controlling redistribution of metals during concurrent metamorphism and deformation is evaluated at the middle amphibolite
facies Montauban deposit in Canada. As at many other deposits, ductile deformation was important in driving mechanical re-mobilisation
of massive sulphides from limb regions into hinge regions of large-scale folds and is thus the most important for controlling
the economics of Pb and Zn distribution. Two possible stages of hydrothermally driven re-mobilisation are discussed, each
of which produces characteristically different alteration assemblages. Prograde hydrothermal re-mobilisation is driven by
pyrite de-sulphidation and concurrent chlorite dehydration and is thus an internally driven process. At Montauban, the H2S-rich fluid generated through this process allowed re-mobilisation of gold into the wall rock, where it was deposited in
response to sulphidation of Fe Mg silicates. Retrograde hydrothermal re-mobilisation is an externally driven process, whereby
large volumes of fluids from outside the deposit may dissolve and re-precipitate metals, and cause hydration of silicate minerals.
This second hydrothermally driven process is not recognised at Montauban. Sulphide melting occurred as temperatures neared
the peak metamorphic conditions. Melting initiated in the massive sulphides through arsenopyrite breakdown, and a small volume
of melt was subsequently re-mobilised into the wall rock. Trace element partitioning and fractional crystallisation of this
melt generated a precious metal-rich fractionate, which remained mobile until well after peak metamorphism. Thus, prograde
hydrothermal re-mobilisation and sulphide melting were the most important mechanisms for controlling the distribution of Au
and Ag. 相似文献