Joint inversion of Rayleigh‐wave dispersion data and vertical electric sounding data: synthetic tests on characteristic sub‐surface models          下载免费PDF全文

M. Senkaya  H. Karslı 《Geophysical Prospecting》2016,64(1):228-246

In the traditional inversion of the Rayleigh dispersion curve, layer thickness, which is the second most sensitive parameter of modelling the Rayleigh dispersion curve, is usually assumed as correct and is used as fixed a priori information. Because the knowledge of the layer thickness is typically not precise, the use of such a priori information may result in the traditional Rayleigh dispersion curve inversions getting trapped in some local minima and may show results that are far from the real solution. In this study, we try to avoid this issue by using a joint inversion of the Rayleigh dispersion curve data with vertical electric sounding data, where we use the common‐layer thickness to couple the two methods. The key idea of the proposed joint inversion scheme is to combine methods in one joint Jacobian matrix and to invert for layer S‐wave velocity, resistivity, and layer thickness as an additional parameter, in contrast with a traditional Rayleigh dispersion curve inversion. The proposed joint inversion approach is tested with noise‐free and Gaussian noise data on six characteristic, synthetic sub‐surface models: a model with a typical dispersion; a low‐velocity, half‐space model; a model with particularly stiff and soft layers, respectively; and a model reproduced from the stiff and soft layers for different layer‐resistivity propagation. In the joint inversion process, the non‐linear damped least squares method is used together with the singular value decomposition approach to find a proper damping value for each iteration. The proposed joint inversion scheme tests many damping values, and it chooses the one that best approximates the observed data in the current iteration. The quality of the joint inversion is checked with the relative distance measure. In addition, a sensitivity analysis is performed for the typical dispersive sub‐surface model to illustrate the benefits of the proposed joint scheme. The results of synthetic models revealed that the combination of the Rayleigh dispersion curve and vertical electric sounding methods in a joint scheme allows to provide reliable sub‐surface models even in complex and challenging situations and without using any a priori information.  相似文献   

基于交叉梯度交替结构约束的二维地震走时与全通道直流电阻率联合反演   总被引：3，自引：3，他引：0       下载免费PDF全文

高级  张海江 《地球物理学报》2016,59(11):4310-4322

在利用不同的地球物理勘探方法对地下复杂介质成像时,因观测系统的非完备性及数据本身对某些岩石物性的不敏感性,单独成像的结果存在较大的不确定性和不一致性.对于地震体波走时成像与直流电阻率成像,均面临着成像阴影区问题.对于地震走时成像,地震射线对低速区域覆盖较差形成阴影区,造成低速区域分辨率降低.对于电阻率成像,电场线在高阻区域分布较少,造成高阻区域分辨率较低.为了提高地下介质成像的精度,Gallado和Meju(2003)提出了基于交叉梯度结构约束的联合地球物理成像方法.在要求不同的物性模型拟合各自对应的数据同时,模型之间的结构要求一致,即交叉梯度趋于零.为了更有效地实现基于交叉梯度的结构约束,我们提出了一种新的交替结构约束的联合反演流程,即交替反演不同的数据而且在反演一种数据时要求对应的模型与另一个模型结构一致.新的算法能够更容易地把单独的反演系统耦合在一起,而且也更容易建立结构约束和数据拟合之间的平衡.基于新的联合反演流程,我们测试了基于交叉梯度结构约束的二维跨孔地震走时和直流电阻率联合成像.合成数据测试表明,我们提出的交替结构约束流程能够很好地实现基于交叉梯度结构约束的联合成像.与单独成像结果相比,地震走时和全通道电阻率联合成像更可靠地确定了速度和电阻率异常.  相似文献   

Discontinuous deformation analysis of super section tunnel surrounding rock stability based on joint distribution simulation     

《Computers and Geotechnics》2017

Based on binocular stereo photography measurement technology, the actual distribution information of joints and fractures in the tunnel face were obtained via image processing and feature extraction, and the preliminary evaluation of surrounding rock stability of Laohushan tunnel was conducted according to surrounding rock classification method. Since all available surrounding rock classification approaches didn’t consider the influences of the size effect of tunnel excavation span and unfavorable geologic bodies such as weak-fracture zones, an improved discontinuous deformation analysis (DDARF) method was adopted to conduct a numerical simulation of the deformation and fracture processes of the surrounding rock. Using the traveling wave method, triangle DDA blocks were automatically generated in the calculation zone, and the block boundaries were divided into real joints and virtual joints. Based on the real joint information obtained via aforementioned photographic measurement, the real joints in the tunnel face were dynamically modified, in order to achieve the simulation of joint distribution. The results revealed that the fracture evolution regularity, deformation failure mechanism, and block dropping phenomenon that the DDARF joint simulation model calculated are in good agreement with actual conditions, while those obtained based on conventional models present differences from field situation. Additionally, focusing on the localised rockfall phenomenon of Laohushan tunnel, the crack extension rate was introduced to conduct a quantitative comparison of the rock crack evolution process with or without anchor supporting. The research results offer practical guidance for field construction and anchorage support scheme optimization.  相似文献   

粤西-桂东四套成矿系统地质特征、成因类型及构造启示   总被引：1，自引：0，他引：1  

郑义  余盼  王岳军  林振文 《岩石学报》2017,33(3):682-694

粤西-桂东地区是我国重要的矿产资源基地,是研究区域成矿作用和大地构造演化耦合关系的理想地区。本文基于粤西-桂东地区四套主要成矿系统的地质特征的研究,结合区域内矿床精确定年和构造演化的研究成果,探讨四套主要成矿系统的成因类型、成矿构造背景及其对钦杭结合带构造演化的启示。其中,广东云浮硫铁矿产于震旦系大绀山组,块状和条带状矿石呈层状产于火山沉积岩系中,是一套与海底热液活动密切相关的VMS成矿系统,形成于新元古代俯冲相关的弧后(间)拉张盆地;盘龙铅锌矿产于泥盆系上伦组,角砾状和胶状矿石产于浅海相白云质碎屑岩中,是一套加里东期被动大陆边缘的SEDEX型铅锌成矿系统;河台金矿田赋存于震旦系乐昌组,脉状矿体严格受断裂和蚀变带控制,是一套变质热液主导的造山型金矿成矿系统,形成于印支-燕山期陆内走滑或陆陆碰撞背景;圆珠顶铜钼矿床形成与燕山期(155Ma)二长花岗斑岩密切相关,细脉浸染状矿石赋存于岩体的内外接触带,是一套陆内伸展背景的斑岩铜钼成矿系统。总体而言,粤西-桂东地区经历了新元古代俯冲、加里东期被动大陆边缘、印支期陆内走滑(或陆陆碰撞)和燕山期陆内伸展四个重要的构造事件,这与钦杭结合带总体构造演化过程一致。  相似文献   

湖南新宁星子岩锑矿流体包裹体特征及矿床成因     

余盼  郑义  王岳军  虞鹏鹏 《地学前缘》2018,25(5):266-276

湖南新宁县星子岩锑矿位于钦杭结合带中段湘中盆地内,脉状矿体受NE向硅化破碎带控制,直接容矿围岩为下寒武统香楠组碳质板岩和硅质板岩。文中对星子岩锑矿进行系统的矿物生成序列研究,将成矿过程分为两期3个阶段,即沉积期以碳质板岩内球状黄铁矿为代表,热液期早阶段脉状辉锑矿石英脉(局部夹围岩角砾)和晚阶段辉锑矿方解石脉。为进一步限定其成因,选取热液期与辉锑矿共生的早阶段石英和晚阶段的方解石进行流体包裹体研究。包裹体岩相学研究表明,热液期石英和方解石内广泛发育流体包裹体,主要类型为纯H2O型和CO2-H2O型流体包裹体。激光拉曼测试表明,CO2-H2O型包裹体气相主要成分为CO2,液相主要成分为H2O。显微测温过程中,当降温时可见CO2-H2O型包裹体由气液两相变为三相,其初熔温度为-60.0~-56.6 ℃,CO2部分均一温度为3.7~28.5 ℃,完全均一温度介于113~266 ℃,CO2笼合物熔化温度为3.0~9.6 ℃,对应的流体盐度w(NaCleqv.)为0.8%~12.0%。星子岩锑矿流体包裹体的中低温、低盐度和含CO2的特征与造山型金矿的变质流体成矿特征相吻合。综合星子岩锑矿的成矿大地构造背景、矿床地质和成矿流体特征,星子岩锑矿的精细成矿过程为：钦杭结合带在印支-燕山期发生强烈的陆壳叠置作用,富碳质含黄铁矿的寒武系地层发生变质变形脱挥发分作用,形成中低温、低盐度、富CO2和富集锑元素的变质热液;变质热液向上运移过程中,温度压力降低发生相分离,导致CO2逸失和流体沸腾作用,大量辉锑矿沉淀,最终形成有经济价值的矿体。湖南星子岩锑矿的矿床地质特征和成矿过程与造山型金矿一致,因此其成因类型为造山型锑矿。  相似文献   

Comparative review of marine mammal guidance implemented during naval exercises     

Sarah J. Dolman  Caroline R. Weir  Michael Jasny 《Marine pollution bulletin》2009,58(4):465-477

This article reviews the types and effectiveness of marine mammal mitigation measures used during some naval activities worldwide. The three main standard methods used to mitigate the potential impacts of naval sonar sound on marine mammals are (1) time/area planning (of exercises/active sonar use) to avoid marine mammals; (2) implementation of operational procedures (e.g. ‘soft start’ - where sound levels are gradually increased over time); and (3) monitoring of animals for the purpose of maintaining an ‘exclusion zone’ around the sound source. Suggestions towards a minimum worldwide mitigation standard are made.  相似文献   

二维复杂层状介质中地震多波走时联合反演成像   总被引：6，自引：3，他引：3       下载免费PDF全文

黄国娇  白超英 《地球物理学报》2010,53(12):2972-2981

采用新近提出的多次波射线追踪正演算法,结合共轭梯度法求解带约束的阻尼最小二乘最优化反演问题,分析讨论了利用多震相走时资料进行联合反演成像的方法及技术.考虑到不同震相走时的拾取误差不同,反演算法中引入了不同震相种类数据的权系数; 由于同时反演速度模型和反射界面起伏中不同模型参数变化对走时影响程度的不同, Jacobi偏导矩阵元素中引入了不同参数的归一化因子; 另外,为了克服射线密度过大(或过小)区域速度模型的过度(或欠)更新问题,反演算法中引入了等权射线密度的概念.几种数值模拟实例表明(含噪声敏感性试验): 多波走时的联合或同时反演成像技术是一种提高走时成像空间分辨率,进而降低重建模型失真度行之有效的方法.  相似文献   

钻井-地表电极联合电阻率观测装置的异常特征研究   总被引：4，自引：0，他引：4       下载免费PDF全文

黄俊革  阮百尧  王家林  张家峰  吕玉增 《地球物理学报》2009,52(5):1348-1362

本文利用有限单元法对多种钻井-地表电极联合电阻率观测装置在球体、直立板和水平板体等典型地质体模型上的异常响应进行正演计算,并分析其异常特征和分布规律.计算结果表明利用井中和地表电极的联合观测方式进行地下介质探测,可在兼顾地质体的水平分辨能力的同时,提高电阻率测深在垂向上分辨率.就水平分辨率而言,四极（偶极）装置对地质体的水平定位能力最强,井-地三极装置次之,地-井三极的分辨能力最差.就垂向分辨能力来说,各种观测装置的分辨率相差不大.  相似文献   

准噶尔盆地北部基底结构与属性问题探讨   总被引：11，自引：3，他引：8       下载免费PDF全文

赵俊猛  黄英  马宗晋  邵学钟  程宏岗  王伟  徐强 《地球物理学报》2008,51(6):1767-1775

准噶尔盆地的基底结构与属性一直是地学界关注的焦点问题之一.横跨准噶尔盆地北部,走向近东西的克拉玛依—喀姆斯特地震剖面提供了该盆地北部详细的地壳与上地幔顶部的速度结构与构造,特别是基底顶界面的速度.沿剖面发现了数条走向近南北的“H”型超壳断裂,它们没有明显的断差,断裂处反射系数明显降低,介质的Q值减小,推测具“开裂”性质;利用盆地内1:20万重磁数据完成了重磁联合反演,获得了沿剖面的地壳与上地幔顶部的二维密度结构与二维磁性结构.根据在一定深度范围内介质的速度-密度-岩性之间的关系,确定了盆地北部基底岩性分布.结果表明,准噶尔盆地北部的基底多处为基性和超基性物质,推测为深部（上地幔）物质沿超壳断裂进入地壳内部并对地壳物质进行改造的结果.这一推断得到盆地内部高磁性、高重力异常的支持,也与盆地具有较高的地壳平均速度相一致.综合其他地球物理与地质资料综合分析,给出了综合地质解释剖面,建立了准噶尔盆地北部基底结构与属性的动力学模型.  相似文献   

Joint PP‐ and PSV‐wave amplitudes versus offset and azimuth inversion for fracture compliances in horizontal transversely isotropic media          下载免费PDF全文

Huaizhen Chen  Guangzhi Zhang  Tiansheng Chen  Xingyao Yin 《Geophysical Prospecting》2018,66(3):561-578

We propose a robust approach for the joint inversion of PP‐ and PSV‐wave angle gathers along different azimuths for the elastic properties of the homogeneous isotropic host rock and excess compliances due to the presence of fractures. Motivated by the expression of fluid content indicator in fractured reservoirs and the sensitivity of Lamé impedances to fluid type, we derive PP‐ and PSV‐wave reflection coefficients in terms of Lamé impedances, density, and fracture compliances for an interface separating two horizontal transversely isotropic media. Following a Bayesian framework, we construct an objective function that includes initial models. We employ the iteratively reweighted least‐squares algorithm to solve the inversion problem to estimate unknown parameters (i.e., Lamé impedances, density, and fracture compliances) from PP‐ and PSV‐wave angle gathers along different azimuths. Synthetic tests reveal that the unknown parameters estimated using the joint inversion approach match true values better than those estimated using a PP‐wave amplitude inversion only. A real data test indicates that reasonable results for subsurface fracture detection are obtained from the joint inversion approach.  相似文献