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1.
矩张量反演理论是研究深部岩体破裂机制的有效手段,而监测台站/传感器校准对获取准确的矩张量结果十分重要。为求得更加准确的校准系数和矩张量结果,提出一种新的传感器校准方法——搜索校准法。将该方法和监测网校准法分别应用于加利福尼亚州北部的Geysers地热田微震监测数据中,并综合考虑不同震源机制参数、预设校准系数、噪声添加方式及噪声水平等因素的影响,进行两种校准方法有效性对比的理论计算和模拟分析。结果表明：两种校准方法均可通过微震监测数据获得稳定的校准系数,且校准后的震源成分及应力状态分布均更加集中;所有模拟工况下,两种校准方法均可有效降低矩张量反演误差;低噪声条件下,两种方法对应的矩张量反演误差较小且十分接近;混合噪声和高噪声条件下,搜索校准法的准确性和稳定性多优于监测网校准法;进而优选出Geysers地热田微震监测数据更加可靠的矩张量结果。研究思路和结论为微地震矩张量研究提供了进一步指导。 相似文献
2.
在裂隙岩体二维柔度张量数值试验的基础上,建立了裂隙岩体三维柔度张量及其表征单元体积（REV）尺度研究的简化数值试验方法。首先根据岩体裂隙的统计参数及分布规律,运用蒙特卡罗方法在研究域内获得与实际岩体裂隙同分布的三维随机裂隙网络,提取位于不同方位的岩体试件,运用二维柔度张量的数值试验方法求出各个平面方向上的二维柔度张量,然后根据二维与三维柔度张量的拓扑关系,用数学方法求解裂隙岩体的三维柔度张量。对于含3组正交全贯通裂隙的岩体,通过数值试验获得的柔度张量与理论解相比,其主对角线上各参数的误差在5%以内,表明该数值试验方法较为可靠。最后将此方法运用到小湾水电站工程中,确定左岸坝区裂隙岩体的应力REV为11 m×11 m×11 m,并获得该区域裂隙岩体的三维柔度张量。 相似文献
3.
Stability of earthquake moment tensor inversions: effect of the double-couple constraint 总被引：1，自引：0，他引：1
We show that spurious large non-double-couple components can be obtained in inversions for the full deviatoric moment tensor for shallow crustal earthquakes due to inaccurate Earth models. The traditional “best double-couple” solution does not in general provide an optimal estimate of a double-couple mechanism, and is only reliable when the non-double-couple component of the full deviatoric solution is small. The inverse problem for the moment tensors of the 1998 Antarctic Plate and 2000 Wharton Basin strike-slip earthquakes is shown in each case to have two well-fitting minima in the misfit function of pure double-couple solutions. Such pairs of solutions are most likely to exist for earthquakes which are close either to vertical strike-slip or to dip-slip on a fault plane dipping at 45°. It is shown theoretically that these pairs of solutions arise from the combination of the pure double-couple constraint and the instability of two elements of the moment tensor. No significant non-double-couple component is found for the shallow thrusting 1996 Biak, Indonesia earthquake. 相似文献
4.
随着传感器技术的发展,重力场与重力张量场测量技术发展迅速,为实现地下密度分布精细反演提供了数据保障。正演是反演的基础,解决任意密度分布复杂地质体重力场与重力张量正演高效、高精度计算问题,是实现重力高效、精细反演、人机交互反演解释的关键。针对起伏地形和任意密度分布这种复杂条件下二维重力场及重力张量场高效高精度正演问题,这里提出了一种空间波数混合域正演算法,其关键环节包括:①结合新的矩形二度体组合模型波数域表达式和一维Gauss-FFT算法,提出了一种任意密度分布和起伏地形下重力场及重力张量高效、高精度正演算法;②采用新的二维正演算法,计算观测最高点和最低点之间多个不同高度水平网格重力场及重力张量,结合三次样条插值方法,实现了起伏地形上重力场及重力张量场高效、高精度正演。模型算例结果表明,新方法具有高效、高精度的显著特点。 相似文献
5.
Since their introduction to the geological literature by Brace (1959, 1960, 1961), Mohr circles for large irrotational deformations have proved valuable as aids to our understanding of deformation geometry. However, confusion persists regarding sign conventions. We show that there are two basic kinds of Mohr circles, each with its distinct set of sign conventions. These two divisions, which we call Mohr circles of the First and Second Kind, are not merely reflections of one another in Mohr space. They represent two distinct aspects of the relationship between the space of tensor components (Mohr space) and the space of geological structures (geographical space). The distinction between Mohr circles of the First and Second Kind is critical when the circles are drawn in off-axis positions for asymmetric tensors. Constructions in Mohr space are described which correspond to various standard tensor operations including transposition, inversion, addition and various kinds of multiplication. For some of these operations Mohr circles of one kind or the other offer advantages. 相似文献
6.
《Tectonophysics》1987,135(4):289-296
The total inversion algorithm (Tarantola and Valette, 1982) is applied to a set of focal mechanisms corresponding to the aftershocks of the southern Italy November 23, 1980 earthquake (Ms = 6.9), and the elements of several stress tensors are computed. The obtained complex distribution of stress for this region is analyzed, and two zones around the main event, corresponding to areas of tension and compression distributed at different depths, are delimited. A stress tensor was sought for a third region, corresponding to events which occurred along the strike of the main event and with magnitudes greater than 2.2, but with ambiguous results. 相似文献
7.
We present a new family of flux continuous, locally conservative, finite volume schemes applicable to the diagonal and full tensor pressure equations with generally discontinuous coefficients. For a uniformly constant symmetric elliptic tensor field, the full tensor discretization is second order accurate with a symmetric positive definite matrix. For a full tensor, an M-matrix with diagonal dominance can be obtained subject to a sufficient condition for ellipticity. Positive definiteness of the discrete system is illustrated. Convergence rates for discontinuous coefficients are presented and the importance of modeling the full permeability tensor pressure equation is demonstrated. 相似文献
8.
淤泥固化技术在国内已经进入到工程应用阶段,明确固化淤泥的压缩特性对于指导淤泥固化工程的设计具有重要意义。通过单因素试验方案对不同初始含水率、不同水泥添加量、不同养护龄期的固化淤泥的压缩特性进行了研究。结果发现,固化淤泥压缩特性的最大特点是存在固结屈服应力,当荷载小于固结屈服应力时固化淤泥的压缩性非常小,而固化淤泥屈服之后的压缩性是屈服前压缩性的20倍以上,并且远大于未处理淤泥的压缩特性。淤泥本身是高压缩性的土,固化处理以后变为中等压缩性和低压缩性的土体。固化淤泥的固结屈服应力随水泥量增加线性增大,龄期越长、含水率越低固结屈服应力越大。固化淤泥的这种在固结屈服应力处发生突变的压缩特性和天然沉积结构性土类似,可以用双对数压缩模式来表示固化淤泥的这种压缩特性。 相似文献
9.
J. A. Tossell 《Physics and Chemistry of Minerals》1992,19(5):338-342
29Si NMR studies on synthetic single crystal forsterite have shown an isotropic NMR shift of –63.2 ppm relative to tetramethyl silane and shift tensor components of –24.4, –7.9 and +32.2 ppm relative to this isotropic value. The most shielded component (+32.2 ppm) lies close to the Si-O1 vector, where Si-O1 is the shortest bond, R(Si-O1)=1.614Å (Weiden and Rager, Z. Naturforsch 40a, 126 (1985)). Ab initio self consistent field molecular orbital calculations using the Random Phase Approximation Localized-Orbital Local-Origin (RPA LORG) method and a polarized split valence basis set yield shift tensor components of –28.9, +2.3 and +26.6 ppm relative to the isotropic value, with the most shielded component 17.6° from the Si-O1 axis. This good agreement is obtained for a SiO
4
4–
cluster with forsterite local geometry stabilized by four +1 point charges, PC, with the 相似文献
10.
为了研究岩石张拉破坏的过程和机制,首先通过模拟计算,验证了加权反演法在进行巴西劈裂试验矩张量求解方面的优越性;其次基于花岗岩的巴西劈裂试验,进行声发射监测、事件定位及矩张量反演,并分析标准反演法和加权反演法对应矩张量结果的差别;使用聚类分析K均值算法对矩张量结果进行分簇研究。研究结果表明：模拟计算中加权反演法可以降低巴西劈裂试验矩张量反演误差;室内花岗岩巴西劈裂试验中,加权反演法较大程度地优化了声发射事件的剪切成分以及压/拉应力轴的分布,使得反演结果更加合理。针对加权反演结果,所有事件可分成3簇,同簇内事件的破裂类型、应力状态、破裂机制、辐射模式等均相近;不同簇中的事件在时空上交叉分布,试验后期在圆盘东?西方向上具有较为明显张拉特性的事件骤增,于圆盘中心附近聚集并占据主导,最终导致试样的宏观破裂。研究结果解释了花岗岩巴西劈裂试验的破裂过程和破裂机制,为岩石力学行为研究提供进一步指导。 相似文献
11.
M. Pistorino F. Nestola T. Boffa Ballaran M. C. Domeneghetti 《Physics and Chemistry of Minerals》2006,33(8-9):593-600
The unit-cell parameters of two columbite samples along the (Fe,Mn)Nb2O6 solid solution were measured by means of high-pressure single-crystal X-ray diffraction up to pressures of 7 GPa. The compressional behaviour of these minerals was studied as a function of composition and degree of order. The P–V data of all the samples were fitted with a third-order Birch–Murnaghan equation of state. For the two samples with different compositions but identical degree of order the substitution of Mn for Fe causes a decrease of the bulk modulus K
T0, from 153(1) to 146(1) GPa, without any effect on the pressure first derivative K′. For the two samples with the same composition, cation ordering causes an increase of the bulk modulus from 149(1) to 153(1) GPa and of the pressure first derivative from 4.1(2) to 4.8(3). The compressional behaviour is anisotropic with a linear axial compressibility scheme β
b
> β
c
≥ β
a
for all samples, regardless of composition and degree of order. Such anisotropy increases sligthly with increasing Mn content. 相似文献
12.
NIED seismic moment tensor catalogue for regional earthquakes around Japan: quality test and application 总被引：4，自引：0，他引：4
We have examined the quality of the National Research Institute for Earth Science and Disaster Prevention (NIED) seismic moment tensor (MT) catalogue obtained using a regional broadband seismic network (FREESIA). First, we examined using synthetic waveforms the robustness of the solutions with regard to data noise as well as to errors in the velocity structure and focal location. Then, to estimate the reliability, robustness and validity of the catalogue, we compared it with the Harvard centroid moment tensor (CMT) catalogue as well as the Japan Meteorological Agency (JMA) focal mechanism catalogue. We found out that the NIED catalogue is consistent with Harvard and JMA catalogues within the uncertainty of 0.1 in moment magnitude, 10 km in depth, and 15° in direction of the stress axes. The NIED MT catalogue succeeded in reducing to 3.5 the lower limit of moment magnitude above which the moment tensor could be reliably estimated. Finally, we estimated the stress tensors in several different regions by using the NIED MT catalogue. This enables us to elucidate the stress/deformation field in and around the Japanese islands to understand the mode of deformation and applied stress. Moreover, we identified a region of abnormal stress in a swarm area from stress tensor estimates. 相似文献
13.
Lain Allison 《Journal of Structural Geology》1984,6(3):331-333
The pole of a Mohr diagram, for the two-dimensional case, is a unique point on the Mohr circle which permits any point on the Mohr circle to be related to the direction in the physical plane associated with that point. A Mohr diagram can be constructed for any second rank tensor. To illustrate the simplicity of this geometrical construction two examples of the use of the pole are presented, one for the strain tensor and the other for the stress tensor. 相似文献
14.
D. Legrand A. Calahorrano B. Guillier L. Rivera M. Ruiz D. Villagmez H. Yepes 《Tectonophysics》2002,344(1-2)
The phreatic activity and the subsequent dacitic dome growth in 1998–1999 at Guagua Pichincha volcano, Ecuador, were associated with two seismic swarms: one located in the northern part of Quito (population: 1,500,000) and another one, just below the active volcano, about 15–20 km SW from the first one. Quito swarm tectonic events have high frequencies (from 1 to 10–15 Hz). We registered more than 3200 events (among which 2354 events of 1.4≤ML≤4.2) between June 1998 and December 1999 at the −2- and −17-km depth. The volcanic events below the Guagua Pichincha caldera have high (from 1 to 10–15 Hz) and low (less than 3 Hz) frequencies. Approximately, 130,000 events were registered between September 1998 and December 1999 at the +2.4- and −3.5-km depth. Here, we study the stress tensors of these two swarms deduced from the polarities of P first motions and compare them to the regional stress tensor deduced from CMT Harvard focal mechanisms. The Quito swarm stress tensor is relatively close to the regional stress tensor (the σ1 axis was oriented N117°E close to the N102°E direction of the plate motion found by the GPS measurement, and σ3 is nearly vertical). The difference may be due to the action of the closely active Guagua Pichincha volcano. The Guagua Pichincha stress tensor is very different from the regional tectonic one. The σ1 axis of the volcano is oriented N214°E, almost perpendicular to the σ1 of the swarm of Quito and σ3 is almost horizontal. Even if these two tensors are different, they can be explained in a more general tectonic scheme. The almost horizontal direction of σ3 just below the volcano is compatible with an extensional horizontal direction that may be expected in the shallow extrados part of a compressional region and consistent with an opening of the top of the Guagua Pichincha volcano. The movement of the fluids (magma, gas and/or groundwater) produced by the closely active Guagua Pichincha volcano seems to have an influence in the acceleration of the generation of seismic events. 相似文献
15.
南宁膨胀土长期压缩特性研究 总被引：5，自引：0，他引：5
膨胀土的结构、胀缩机制、力学特性和改良方法等方面已有广泛研究,但关于膨胀土长期压缩特性研究甚少,而需对膨胀土地区路基长期稳定性、隧道开挖对地基及地下构筑物长期影响的研究,使得膨胀土长期压缩特性的研究变得尤为重要。采用取自南宁地铁东站某基坑膨胀土进行长期一维压缩试验,研究固结压力、含水率分别对压缩指数 、次压缩系数 的影响、压缩指数 与次压缩系数 的关系、预压处理和石灰处治对膨胀土长期压缩特性的影响,寻求降低膨胀土次压缩性的最佳方案。试验结果表明,南宁膨胀土的压缩指数与次压缩系数呈线性关系;与其他黏土相比,膨胀土次压缩特性较低;预压处理和改良处理可以减小土体的次压缩性,经预压处理的改良膨胀土次压缩性最低。 相似文献
16.
George A. Lager 《Physics and Chemistry of Minerals》1978,3(3):237-249
When a crystalline solid is subjected to a temperature increase, its constituent polyhedra may change in size and shape and rotate relative to one another. If the deformation can be approximated by a linear transformation of atomic coordinates, these changes can be quantitatively described in terms of second rank tensors. An iterative least-squares method is used to calculate strain and rotation tensors given the positions of the coordinating atoms of a polyhedron at two temperatures. The method is applied to polyhedral thermal expansions in silicate and oxide minerals. 相似文献
17.
Franti
ek Hrouda 《Tectonophysics》2002,347(4)
The anisotropy of magnetic susceptibility (AMS) is often controlled by both ferromagnetic (sensu lato) and paramagnetic minerals. The anisotropy of magnetic remanence (AMR) is solely controlled by ferromagnetic minerals. Jelínek (Trav. Geophys. 37 (1993)) introduced a tensor derived from the isothermal AMR whose normalized form equals the normalized susceptibility tensor provided that the ferromagnetic fraction is represented by multi-domain magnetite. The present paper shows the close correlation between these tensors for a collection of strongly magnetic specimens containing multi-domain magnetite. In addition, acceptable correlation between the tensors was also found for a collection of specimens containing single-domain magnetite. A new method is developed for the AMS resolution into ferromagnetic and paramagnetic components using the AMR. Some examples are presented of this resolution in mafic microgranular enclaves in granodiorite and in gneisses of the KTB borehole. 相似文献
18.
19.
The average seismic strain rate is estimated for the seismotectonic zone of the northern/central parts of the Gulf of Suez. The principal strain rate tensor and velocity tensor were derived from a combination of earthquake focal mechanisms data and seismic moment of small-sized earthquakes covering a time span of 13 years (1992–2004). A total of 17 focal mechanism solutions have been used in the calculation of the moment tensor summation. The local magnitudes (MLs) of these events range from 2.8 to 4.7. The analysis indicates that the dominant mode of deformation in the central and northern parts of the Gulf of Suez is extension at a rate of 0.008 mm/year in N28°E direction and a small crustal thinning of 0.0034 mm/year. This low level of strain means that this zone experienced a little seismic deformation. There is also a right lateral shear motion along the ESE–WNW direction. This strain pattern is consistent with the predominant NW–SE normal faulting and ESE–WNW dextral transtensive faults in this zone. Comparing the results obtained from both stress and strain tensors, we find that the orientations of the principal axes of both tensors have the same direction with a small difference between them. Both tensors show a predominantly extensional domain. The nearly good correspondence between principal stress and strain orientations in the area suggests that the tectonic strength is relatively uniform for this crustal volume. 相似文献
20.
A relation between hardness (H) for minerals and compressibility (β) is proposed: \(H = \frac{M}{{\rho q\beta }}\) , where M is the molecular weight, ρ the density and q the number of atoms in a formula unit. The relation is derived from thermodynamics and is based on an analogy between mineral hardness and the concept of hardness assumed for the classification of reactivity of molecular species. It is confirmed with 27 elemental solids and 66 crystalline compounds, that this simple relation fairly well describes the trend of experimental hardnesses of minerals, and that the new relation has advantages over one earlier proposed [Plendl et al. (1965)] for connecting hardness to compressibility. 相似文献