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1.
正随着CT技术和其他专业学科的发展,CT理论与技术在工业、地球物理、医学影像、工程勘探、无损探测、现代农业、安全检测等领域得到了广泛的应用。目前医学成像还广泛涉及MRI、PET、SPECT、超声、心电、脑电、EPRI等传统和新兴成像方式。与之相对应,图像分析涉及数 相似文献
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随着城市化的发展,城市地球物理日益成为地球物理研究的重要方向,地震成像是构建城市地下空间三维/四维图像的重要手段,但面临观测成本高的困难.近年来国际上新发展的分布式光纤声波传感器作为高密度地震观测系统已经在地震层析成像方面得到了应用,在提高成像分辨率的同时,又降低了观测成本.本研究使用国产分布式光纤声波传感器开展了观测实验,利用480m埋地光缆记录了13h背景噪声,计算得到噪声互相关函数,获得了高频Rayleigh面波信号.采用多道面波分析方法提取相速度频散曲线,其结果与传统检波器记录和主动源结果较为一致.采用遗传算法反演得到了研究区内二维S波速度剖面,获得了下方沉积物横向变化特征.通过本次实验,初步验证了国产设备开展地震背景噪声成像研究、构建地下浅层结构模型的可行性. 相似文献
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《CT理论与应用研究》2018,(5)
正随着CT技术和其他专业学科的发展,CT理论与技术在工业、地球物理、医学影像、工程勘探、无损探测、现代农业、安全检测等领域得到了广泛的应用。目前医学成像还广泛涉及MRI、PET、SPECT、超声、心电、脑电、EPRI等传统和新兴成像方式。与之相对应,图像分析涉及数字图像处理、模式识别、深度学习、大数据等传统和新兴分析工具。将二者有效地综合研究与应用已成为当下的热点,具有广阔的研究和应用前景。 相似文献
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《CT理论与应用研究》编辑部 《CT理论与应用研究》2003,12(4):49-52
目的: 通过2003年国际地球物理大会(IUGG)了解国际上关于地球断面成像和灾害预测的某些主流的信息,向读者提供前缘信息. 资料和方法:本文所概括和摘录的信息来自 2003 IUGG Program & Abstracts 光盘, 选择其与本刊密切有关的内容供交流.结论:火山喷发与洪水的预测可以为预测地震有所借鉴;对于地下物理参数的三维探测,成像演示,其分辨率的增加会引起预报模型发生质的变化,利用高精度的三维速度结构以改进火山的预测工作. 相似文献
5.
辽宁及邻区地壳上地幔三维速度的地震成析成像 总被引：2，自引：0，他引：2
引言在过去的 2 0年中层析成像技术应用于许多科学和技术领域 ,其中 ,70年代 CT的出现 ,引起了医学放射诊断学的革命 ,并产生了巨大的影响。自那时以来 ,CT技术在许多学科 ,如在地球物理勘探、射电天文学、遥感技术及各应用科学中得到了广泛应用。在地球物理学中 ,地震层析成像的研究大约开始于 70年代后期 ,是取得地壳上地幔三维速度结构图像的一种有效方法 ,我国很多地区采用这种方法对地壳速度结构进行了研究 ,取得了良好的效果。如刘福田用近年来发展的正交投影算子方法对中国大陆中东部地区进行了速度结构成像研究。辽宁及邻区的地震… 相似文献
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本文评述了过去60年内固体地球内部几何结构和物性结构成像的进展，包括地震学研究的进展；重磁位场研究的进展；电磁学研究的进展.文章还指出了他们进一步发展的某些方面. 相似文献
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基于高精度的三维波场模拟和伴随方法, 伴随成像成功实现了天然地震全波形成像在区域和全球尺度下的应用。伴随成像技术基于谱元法, 使用全三维、 多参数的初始模型对地震波场进行数值模拟, 通过正演波场和伴随波场的相互作用快速求取目标函数的梯度, 结合高性能计算技术, 实现大尺度全波场成像。相比于传统的地震层析成像方法, 伴随成像对地球内部结构异常体的描述更加精细和全面, 更适用于构造活跃地区的深部动力学研究。本文首先介绍伴随成像方法的基本原理, 随后阐述其具体实现流程, 并回顾该方法在地球深部结构研究中的应用, 最后对其未来发展做出展望。 相似文献
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随着科学技术的迅速发展,对图象处理的要求越来越高,因而各种图象处理技术应运而生,CT(computcrized Tomography)技术就是其中极为有效的方法之一。在医学上的X射线CT成象技术已取得了很大的发展,而将CT成象技术应用于地球参数的反演成像只是近几年才受到人们的普遍关注,虽然利用CT直接成像进行地震反演取得了一定的成果,但是利用CT技术实现地球参数的直接成象还面临着一定的困难。本文试图应用医学上的超声CT成象技术,作数学和物理模型的地球物理CT成象,寻求地球物理CT成象提高精度和分辩率的途径,探讨关于地震层析成象应用的影响因素和限制条件,当然,由于地球物理反演的复杂性和特殊性,必须把医学CT与基本的地球物理方法结合起来这样,才能充分发挥CT技术的作用。我们对井间地震数据进行地震层析成象研究,这主要是由于井间地震学的研究目前已成为一个有意义的研究课题,与传统的反射地震学相比,它有以下特点: (1) 井中震源和井中检波器可以避免地表风化层,减少高频信号的损失,为提高分辩率打下了物理基础。 (2) 井间地震可以把震源和检波器的排列直接布置在目标层的附近,避免了波在从地面到目标标层漫长的往返传播中所受的损失。这也可以使接收到的地震信号能保留更高频率的有效成分。 (3) 井间地震是从不同的角度来探测目标,可利用直接透射波,这就有可能探测目标的低频成分,并对目标层内的速度分布进行成象,这是地表反射地震学所不能比拟的。 相似文献
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《地球物理学进展》2015,(1)
海洋地震勘探中多次波非常发育,如何合理处理多次波是一个很重要的课题.本文首先对海上多次波的产生机理、分类及识别方式进行了回顾,然后对目前国内外发展的多次波处理技术进行了总结.文中从将多次波作为噪音和将多次波视为有效信息,即多次波压制与成像这两个方面分别进行了总结.多次波在一次波成像中的严重干扰推动了多次波压制技术的不断发展,主要发展了基于滤波理论和基于波动理论的两大类多次波压制方法,但是综合考虑计算效率和多次波压制精度,近年来,将两种方法相结合成为一种新的发展趋势;而多次波作为来自地下界面的真实反射也包含了丰富的地下信息,目前,诸多地球物理学家分别从对多次波进行单独成像和对一次波和多次波联合成像的角度对多次波的有效利用开展了大量研究,结果显示利用多次波可以获取比一次波更多的地下信息,但是该技术发展还不够成熟,这将需要广大地球物理工作者继续开展深入的研究. 相似文献
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徐闻地区位于北部湾盆地向雷州半岛的延伸部分,具有较好的油气勘探前景.2003年至今,江苏油田在徐闻地区先后开展了重力、大地电磁测深、二维地震和三维地震,以及钻探、VSP和试油测试等油气勘探工作.徐闻地区存在比较特殊的地表与地下地质条件.工区跨越半岛陆上和浅海水域,浅表层多套火成岩覆盖(出露),深层构造破碎、地震反射成像困难.因此,开展了具有针对性的综合地球物理方法(重力、大地电磁测深和地震)研究与勘探实践,克服了单一地球物理方法的局限性,获得了较好的数据资料,减少了多解性并为该地区的油气发现奠定基础. 相似文献
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In order to perform resistivity imaging, seismic waveform tomography or sensitivity analysis of geophysical data, the Fréchet derivatives, and even the second derivatives of the data with respect to the model parameters, may be required. We develop a practical method to compute the relevant derivatives for 2.5D resistivity and 2.5D frequency-domain acoustic velocity inversion. Both geophysical inversions entail the solution of a 2.5D Helmholtz equation. First, using differential calculus and the Green's functions of the 2.5D Helmholtz equation, we strictly formulate the explicit expressions for the Fréchet and second derivatives, then apply the finite-element method to approximate the Green's functions of an arbitrary medium. Finally, we calculate the derivatives using the expressions and the numerical solutions of the Green's functions. Two model parametrization approaches, constant-point and constant-block, are suggested and the computational efficiencies are compared. Numerical examples of the derivatives for various electrode arrays in cross-hole resistivity imaging and for cross-hole seismic surveying are demonstrated. Two synthetic experiments of resistivity and acoustic velocity imaging are used to illustrate the method. 相似文献
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波动方程基准面校正处理被认为是当地表高程变化剧烈、地表一致性假设又不成立的情况下对于常规高程基准面校正的必要替代. 在二维波动方程基准面校正方面，前人已经作了大量工作，并且在实际应用中获得了良好的效果，应该将其进一步推广到三维. 本文采用三维频率空间域有限差分波场延拓算子以“逐步－累加”的方式实现了三维波动方程基准面校正，并对实际数据进行了处理. 对于西部某三维数据的实际计算结果表明，相对于传统的模型法高程静校正，波动方程基准面校正更合理地实现了基准面校正，有助于提高后续的速度分析精度和成像质量. 相似文献
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Albert Casas Pietro L. Cosentino Gianluca Fiandaca Mahjoub Himi Josep M. Macias Raffaele Martorana Andreu Muñoz Lluís Rivero Roger Sala Imma Teixell 《Surveys in Geophysics》2018,39(6):1107-1124
An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious veneration. Finally, both ERT and GPR have been conducted during a week of intensive overnight surveys that provided detailed information on subsurface existing structures. The ERT method has been applied using different techniques and arrays, ranging from standard Wenner–Schlumberger 2D sections to full 3D electrical imaging with the advanced Maximum Yield Grid array. Electrical resistivity data were recorded extensively, making available many thousands of apparent resistivity data to obtain a complete 3D image after a full inversion. In conclusion, some significant buried structures have been revealed providing conclusive information for archaeologists. GPR results provided additional information about shallowest structures. The geophysical results were clear enough to persuade religious authorities and archaeologists to conduct selected excavations in the most promising areas that confirmed the interpretation of geophysical data. In conclusion, the significant buried structures revealed by geophysical methods under the cathedral were confirmed by archaeological digging as the basement of the impressive Roman Temple that headed the Provincial Forum of Tarraco, seat of the Concilium of Hispania Citerior Province. 相似文献
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《Journal of Applied Geophysics》2008,64(3-4):103-116
Karstic conduits play a crucial role for water supply in many parts of the world. However, the imaging of such targets is generally a difficult task for most geophysical methods. Magnetic Resonance Sounding (MRS) is a geophysical method designed for imaging of water bearing structures. Initially, MRS was developed for characterizing horizontally stratified aquifers. However, when applying a 1D MRS measuring setup to the imaging of 2D–3D targets, the size of which may be much smaller than the loop, the accuracy and the lateral resolution may not be sufficient. We have studied the possibility of simultaneously processing several MRS aligned along a profile to perform a Magnetic Resonance Tomography (MRT). This work emphasizes the gain of resolution for 2D–3D imagery of MRT versus the interpolation of 1D inversion results of MRS along the same profile. Numerical modelling results show that the MRT response is sensitive to the size and location of the 2D target in the subsurface. Sensitivity studies reveal that by using the coincident transmitting/receiving (TX/RX) setup and shifting the loop around the anomaly area, the depth, section and position of a single karstic conduit with a size smaller than the MRS loop size can be resolved. The accuracy of the results depends on the noise level and signal level, the latter parameter being linked to the depth and volume of the karstic conduit and the water content in the limestone matrix. It was shown that when applying MRT to the localization of 2D anomalies such as karstic conduits, the inclination of the geomagnetic field, the orientation of the MRT profile and the angle of crossover of the conduit by the MRT profile must be taken into account. Otherwise additional errors in interpretation should be expected. A 2D inversion scheme was developed and tested. Both numerical and experimental results confirm the efficiency of the developed approach. 相似文献
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近年来,"两宽一高"——宽频带、宽方位和高密度——三维地震采集技术极大地提升了地震勘探的能力和精度,在岩性油气藏地区取得了明显的应用效果,也对地震采集观测系统设计提出了更高的要求.如何在现有的成本限制和装备条件下,根据具体工区的地质地球物理条件来选择合适的"两宽一高"采集观测参数以实现最佳的勘探效益,已成为当前地震勘探中迫切需要解决的瓶颈问题之一.基于此,本文首先回顾了点绕射聚焦分析的基本原理,随后给出一种新的复杂介质多频率快速聚焦分辨率定量分析方法.基于该理论,我们以一个典型的陆上三维地震勘探采集方案和速度模型为例,系统地研究了"两宽一高"地震资料偏移成像分辨率随着关键采集参数的变化规律,给出了不同条件下分辨率的理论极限值及其所对应的采集参数的临界点值.此外,我们也提出了一种新的采集参数和子波频谱的交汇定量分析方法,进一步阐明了采集参数和子波频谱参数之间的定量关系,为复杂接收激发条件下采集观测系统设计提供了新的理论依据. 相似文献
17.
J.-F. Girard M. Boucher A. Legchenko J.-M. Baltassat 《Journal of Applied Geophysics》2007,63(3-4):103-116
Karstic conduits play a crucial role for water supply in many parts of the world. However, the imaging of such targets is generally a difficult task for most geophysical methods. Magnetic Resonance Sounding (MRS) is a geophysical method designed for imaging of water bearing structures. Initially, MRS was developed for characterizing horizontally stratified aquifers. However, when applying a 1D MRS measuring setup to the imaging of 2D–3D targets, the size of which may be much smaller than the loop, the accuracy and the lateral resolution may not be sufficient. We have studied the possibility of simultaneously processing several MRS aligned along a profile to perform a Magnetic Resonance Tomography (MRT). This work emphasizes the gain of resolution for 2D–3D imagery of MRT versus the interpolation of 1D inversion results of MRS along the same profile. Numerical modelling results show that the MRT response is sensitive to the size and location of the 2D target in the subsurface. Sensitivity studies reveal that by using the coincident transmitting/receiving (TX/RX) setup and shifting the loop around the anomaly area, the depth, section and position of a single karstic conduit with a size smaller than the MRS loop size can be resolved. The accuracy of the results depends on the noise level and signal level, the latter parameter being linked to the depth and volume of the karstic conduit and the water content in the limestone matrix. It was shown that when applying MRT to the localization of 2D anomalies such as karstic conduits, the inclination of the geomagnetic field, the orientation of the MRT profile and the angle of crossover of the conduit by the MRT profile must be taken into account. Otherwise additional errors in interpretation should be expected. A 2D inversion scheme was developed and tested. Both numerical and experimental results confirm the efficiency of the developed approach. 相似文献
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Michael S. Zhdanov 《Geophysical Prospecting》2009,57(4):463-478
The interpretation of potential and electromagnetic fields observed over 3D geological structures remains one of the most challenging problems of exploration geophysics. In this paper I present an overview of novel methods of inversion and imaging of gravity and electromagnetic data, which are based on new advances in the regularization theory related to the application of special stabilizing functionals, which allow the reconstruction of both smooth images of the underground geological structures and models with sharp geological boundaries. I demonstrate that sharp-boundary geophysical inversion can improve the efficiency and resolution of the inverse problem solution. The methods are illustrated with synthetic and practical examples of the 3D inversion of potential and electromagnetic field data. 相似文献