黏声介质最小平方逆时偏移   总被引：12，自引：7，他引：5       下载免费PDF全文

李振春  郭振波  田坤 《地球物理学报》2014,57(1):214-228

介质的黏滞性是普遍存在的.黏滞性介质中的真振幅成像需要校正由介质的黏滞性引起的振幅衰减与速度频散,然而常规的反Q偏移方法存在不稳定问题.本文在反演的框架下求解黏声介质成像问题,在有效避开不稳定的同时实现真振幅成像.首先将波动方程线性化,并依此建立黏声介质最小平方逆时偏移（LSRTM）的目标函数;然后推导波动方程伴随算子,并在此基础上借助伴随状态法推导迭代求解的具体算法;最后通过引入动态相位编码技术将计算量降至与常规逆时偏移相同的数量级.该方法在真振幅成像过程中考虑了介质黏滞性的影响,更接近实际情况,具有更好的振幅保持性.相对于常规逆时偏移,该方法能够自动压制成像噪声,具有更高的成像分辨率及精度.通过模型试算验证了方法的正确性.  相似文献   

反渗透海水淡化水的市政应用研究          下载免费PDF全文

王晓楠  潘献辉  郝军  刘昱 《海洋开发与管理》2017,34(12):77-80

反渗透海水淡化水具有洁净、纯度高和供给稳定的特点,可缓解淡水资源匮乏的问题。文章介绍海湾国家、美国和中国反渗透海水淡化水市政应用现状以及一些典型案例,在此基础上,提出政策扶持和企业协调并重、推进装备核心部件和关键技术国产化以及建立健全相关标准和加强监管等建议,以期促进我国反渗透海水淡化水的大规模市政应用。  相似文献   

拉东投影法三维叠前深度偏移   总被引：6，自引：0，他引：6       下载免费PDF全文

黄新武  吴律  宋炜 《地球物理学报》2004,47(2):321-326

对地下地质构造进行正确成像是地震勘探的最终目的,由于三维地震资料采集不可能都沿垂直构造走向的方向进行,为地震资料的三维处理带来了许多困难. 本文将三维叠后拉东投影偏移思想应用于三维叠前处理中,提出了三维叠前投影偏移算法. 利用拉东投影变换的原理,将整个三维叠前数据体投影到一系列各方向的径向线上,各方位角的构造都包含在其中某条或多条径向剖面上. 投影完成后,形成一系列的独立的二维叠前测线,可采用二维叠前深度偏移成像方法来实现各径向线的叠前偏移,当各径向剖面偏移完成后,在时间切片上进行反投影,从而最终形成三维叠前深度偏移结果. 实际应用表明,用本方法进行三维叠前深度偏移时,深度偏移剖面对横向分辨率有所提高,对陡地层和小断层的成像效果有所改善.  相似文献   

The Widdington Sands: High-level Kesgrave Sands and Gravels near the Cam-Stort interfluve,Northwest Essex,UK     

Colin A. Baker 《Proceedings of the Geologists' Association. Geologists' Association》2019,130(5):559-581

A small but stratigraphically significant exposure of Quaternary sandy sediments (Widdington Sands) was observed and recorded in the early 1970s in northwest Essex. These data are here re-examined and re-evaluated, yielding new insights into early proto-Thames aggradation following the marine recession of the Norwich Crag Formation (MIS 74–71, about 2 Ma). As the proto-Thames trajectory shifted south eastwards, a period of landscape stability ensued in the early Middle Pleistocene (MIS 19–13) during which the Valley Farm Soil was formed. This and the succeeding Barham Soil can be recognised in the stratigraphy, the second palaeosol heralding the arrival of glaciation in the Anglian Stage (MIS 12, 480–420 ka). These pedogenic signatures are enclosed within palaeokarstic features in the form of infilled sinkhole pipes. A large doline has functioned as a sediment trap preserving pre-truncation structures including reverse ring faults. These confirm basal support removal leading to upward migration of a dissolution cavity and roof collapse within the sinkhole pipe. The process and timing of subsidence can thus be defined more clearly than for similar features found in comparable Kesgrave aggradations of the Middle Thames. The likely glacitectonic origin of the planar sub-till surface is examined and discussed. Dating of Early Pleistocene fluvial activity is constrained by estimating the height of a former terrace surface whose elevation points to a correlation with the higher Stoke Row Member (MIS 64, 1.8 Ma), suggesting the oldest known proto-Thames activity within southern East Anglia.  相似文献   

适合中小型企业网络的Web信息发布技术研究     

吴迪  李文印  陈震 《地球物理学进展》2003,18(4):752-757

针对中小型企业网络的特点，讨论了三种适合中小型企业网络的Web信息发布技术：基于域名的虚拟主机、反向代理和NAT端口转发技术，分别以具体实现工具及配置实例讨论了它们的实现过程。最后，比较了这三种实现技术各自的优缺点，并给出了部署建议。  相似文献   

纵横波独立成像的弹性波逆时偏移方法          下载免费PDF全文

尧德中  周熙襄 《地球物理学报》1993,36(5):665-673

本文采用逆时递推,在空间域完成纵横波分离,同时实现了位移场成像和纵、横波的独立成像。模拟数据与实际资料试算表明,对纵波和横波分别成像不仅有理论意义,而且有明显的应用价值。文中还就偏移速度对成像结果的影响和实际资料的预处理问题进行了讨论。  相似文献   

Jurassic extension and Cenozoic inversion tectonics in the Asturian Basin,NW Iberian Peninsula: 3D structural model and kinematic evolution     

《Journal of Structural Geology》2016

We constructed a geological map, a 3D model and cross-sections, carried out a structural analysis, determined the stress fields and tectonic transport vectors, restored a cross section and performed a subsidence analysis to unravel the kinematic evolution of the NE emerged portion of the Asturian Basin (NW Iberian Peninsula), where Jurassic rocks crop out. The major folds run NW-SE, normal faults exhibit three dominant orientations: NW-SE, NE-SW and E-W, and thrusts display E-W strikes. After Upper Triassic-Lower Jurassic thermal subsidence, Middle Jurassic doming occurred, accompanied by normal faulting, high heat flow and basin uplift, followed by Upper Jurassic high-rate basin subsidence. Another extensional event, possibly during Late Jurassic-Early Cretaceous, caused an increment in the normal faults displacement. A contractional event, probably of Cenozoic age, led to selective and irregularly distributed buttressing and fault reactivation as reverse or strike-slip faults, and folding and/or offset of some previous faults by new generation folds and thrusts. The Middle Jurassic event could be a precursor of the Bay of Biscay and North Atlantic opening that occurred from Late Jurassic to Early Cretaceous, whereas the Cenozoic event would be responsible for the Pyrenean and Cantabrian ranges and the partial closure of the Bay of Biscay.  相似文献   

Diffraction imaging by prestack reverse‐time migration in the dip‐angle domain          下载免费PDF全文

Raanan Dafni  William W. Symes 《Geophysical Prospecting》2017,65(Z1):295-316

Prestack image volumes may be decomposed into specular and non‐specular parts by filters defined in the dip‐angle domain. For space‐shift extended image volumes, the dip‐angle decomposition is derived via local Radon transform in depth and midpoint coordinates, followed by an averaging over space‐shifts. We propose to employ prestack space‐shift extended reverse‐time migration and dip‐angle decomposition for imaging small‐scale structural elements, considered as seismic diffractors, in models with arbitrary complexity. A suitable design of a specularity filter in the dip‐angle domain rejects the dominant reflectors and enhances diffractors and other non‐specular image content. The filter exploits a clear discrimination in dip between specular reflections and diffractions. The former are stationary at the specular dip, whereas the latter are non‐stationary without a preferred dip direction. While the filtered image volume features other than the diffractor images (for example, noise and truncation artefacts are also present), synthetic and field data examples suggest that diffractors tend to dominate and are readily recognisable. Averaging over space‐shifts in the filter construction makes the reflectors? rejection robust against migration velocity errors. Another consequence of the space‐shift extension and its angle‐domain transforms is the possibility of exploring the image in a multiple set of common‐image gathers. The filtered diffractions may be analysed simultaneously in space‐shift, scattering‐angle, and dip‐angle image gathers by means of a single migration job. The deliverables of our method obviously enrich the processed material on the interpreter's desk. We expect them to further supplement our understanding of the Earth's interior.  相似文献   

用逆转录聚合酶链式反应检测草鱼出血病病毒的研究   总被引：4，自引：1，他引：4  

王铁辉  李军  易咏兰  周立冉  刘汉勤  陆仁后  陈宏溪 《海洋与湖沼》1997,28(1):1-6

于1994年5月-1995年7月，根据已克隆的草鱼出血病病毒GCHV-861株cDNA的部分序列，设计合成了两对PCR引物，采用RT-PCR技术对GCHV-861及GCHV-873两病毒株的dsRNA进行扩增。结果表明，两对引物仅能特异地检测出GCHV-861病毒株核酸的存在，而不能对GCHV-873病毒株的核酸进行特异扩增，该方法最小可检测出0.1Pg纯化的GCHV-861病毒dsRNA;采用该方法对GCHV-861人工感染的草鱼和稀有鲫组织进行RT-PCR检测，不仅能检测到发病期显症病鱼中GCHV-861病毒的存在，还能检测发病前期及愈后无出血病症状的病毒携带者中病毒的存在;利用该方法还从本所关桥实验场出血病流行季节收集的发病草鱼体内检测出GCHV的存在，说明所设计的引物具有一定的实际意义;利用该法还能检测出感染病毒的组织培养细胞系GCK和CIK上清液中GCHV的存在。还建立了简易的模板制备方法，采用该方法整个检测过程只需3-4h，可大大缩短检测时间。由此可见，RT-PCR技术是检测GCHV的快速、灵敏而特异的方法，发展和完善该技术对草鱼出血病的早期诊断和防治、抗病育种具有重要意义。  相似文献   

逆插支流的演变与河流掉向的关系   总被引：1，自引：0，他引：1  

廖喜林 《地质灾害与环境保护》1999,10(2):14-17

逆插支流是相对正插和顺插支流而言,它们之间的演变过程,受到新构造运动、流水地质作用等诸因素的影响。尤其是逆插支流的演变,对主干河流是否掉向,意义重大,但不是所有逆插支流都对指示主干河流掉向有意义。试图从演变的角度,来剖析逆插、正插和顺插支流的内在联系,以求探讨上述问题。  相似文献