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一种新地震定位方法研究 总被引：2，自引：0，他引：2
提高地震定位精度一直是地震学应用研究的重要课题之一,目前已经发展了多种方法用于台网定位。这些方法的共同弱点是应对复杂情况的能力差、震后处理时间过长、不能根据地震信息的增加自动修改速度模型而提高下一次地震定位的精度。开发地震台网资源,使之实现地震预警的功能,必须解决地震快速定位问题。为此,本文提出了一种基于地震台网资料的网格化地震定位方法。震前建立每个区间网格到台站的理论走时数据库,震时仅通过优化搜索,以每两个台站的到时差与理论走时差之间的方差最小的网格位置为震源,并得到发震时刻。通过在黑龙江省地震台网的实际应用说明方法可靠,精度较高。 相似文献
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地震波的运动学信息(走时、斜率等)通常用于宏观速度建模.针对走时反演方法,一个基本问题是走时拾取或反射时差的估计.对于成像域反演方法,可以通过成像道集的剩余深度差近似计算反射波时差.在数据域中,反射地震观测数据是有限频带信号,如果不能准确地确定子波的起跳时间,难以精确地确定反射波的到达时间.另一方面,如果缺乏关于模型的先验信息,则很难精确测量自地下同一个反射界面的观测数据同相轴和模拟数据同相轴之间的时差.针对走时定义及时差测量问题,首先从叠前地震数据的稀疏表达出发,利用特征波场分解方法,提取反射子波并估计局部平面波的入射和出射射线参数.进一步,为了实现自动和稳定的走时拾取,用震相的包络极值对应的时间定义反射波的到达时,实现了立体数据中间的自动生成.理论上讲,利用包络极值定义的走时大于真实的反射波走时,除非观测信号具有无限带宽(即delta脉冲).然而,走时反演的目的是估计中-大尺度的背景速度结构,因此走时误差导致的速度误差仍然在可以接受的误差范围内.利用局部化传播算子及特征波聚焦成像条件将特征波数据直接投影到地下虚拟反射点,提出了一种新的反射时差估计方法.既避免了周期跳跃现象以及串层等可能性,又消除了振幅因素对时差测量的影响.最后,在上述工作基础之上,提出了一种基于特征波场分解的新型全自动反射走时反演方法(CWRTI).通过对泛函梯度的线性化近似,并用全变差正则化方法提取梯度的低波数部分,实现了背景速度迭代反演.在理论上,无需长偏移距观测数据或低频信息、对初始模型依赖性低且计算效率高,可以为后续的全波形反演提供可靠的初始速度模型.理论和实际资料的测试结果证明了本文方法的有效性. 相似文献
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本文提出了时域多通道相关检测函数并用其计算波形互相关走时差数据,采用双差定位法对2012年9月7日云南彝良地震和余震序列共944个地震进行重定位,得到652个重定位事件,并与目录数据的结果进行了对比.本文采用了多个准则对走时差数据进行筛选,确保定位结果稳定可靠.得到MS5.7主震的震中为27.516°N,103.951°E,震源深度6.9km;MS5.6主震的震中为27.543°N,104.023°E,震源深度7.27km;重定位结果显示,地震序列紧缩为条带状并沿附近断裂走向分布,深度总体分布较重定位前变浅,集中分布在5~8km,地震群出现轻微倾斜.东西向、南北向、深度和发震时刻的平均相对误差分别为55.2 m,43.0 m,186.7 m和0.01s,走时残差16ms.研究表明:互相关数据的结果要优于目录数据;震源深度与速度模型存在较大的相关性;确定彝良—会泽断裂为本次彝良地震序列的发震构造. 相似文献
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《应用地球物理》2020,(1)
碳酸盐岩缝洞型储层所含缝、洞尺度差异大、岩性和速度变化剧烈,造成复杂的绕射响应特征。部分缝洞体尺度小产生的绕射能量较弱,在成像剖面上被连续反射层掩盖,而难以识别。基于此,本文发展了一种倾角域道集的绕射波成像方法,提高对成像剖面上小尺度绕射构造的分辨能力。借助高斯束偏移技术抽取倾角域成像点道集,根据在倾角域道集上绕射同相轴拟线性、反射能量拟抛物的几何形态差异,基于斜率分析方法实现波场分离,并采用汉宁窗函数提高绕射波分离效果,将分离后的绕射波倾角域道集水平叠加得到绕射波成像结果。理论分析和数值模型测试结果表明:在窗函数的基础上,应用基于斜率分析的波场分离方法得到的绕射波倾角域道集能够更好的压制噪声,叠加后的绕射波成像剖面中绕射构造更加清晰。 相似文献
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震源定位是微地震监测关键技术之一。本文提出用于微地震定位的弹性波和加权弹性波(WEW)干涉成像方法。该方法在保证定位精度的同时,还可避免震源假象。通过各向同性水平层介质状模型的数值试验,初步表明该方法可适应低信噪比微震信号、速度随机扰动、较稀疏的检波器分布等情况,并在速度模型存在一定的系统误差时也仍保持较高的定位精度。由于干涉成像方法不需要进行初至拾取,定位效率相对传统走时方法也得到了提高。采用二维断层模型试算Nnumerical results of using a two-dimensional fault model,表明方法还能实现多震源定位,且比逆时成像有更高的定位精度。 相似文献
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由于地震定位受发震时刻与震源深度间强烈的折衷关系的困扰及反演问题的非线性影响,该问题一直未得到根本解决. 为此,本文提出了一种新的定位方法--SAMS法,该方法利用走时残差和到时残差之绝对值极小作为目标函数,用快速模拟退火法求解反演问题的解答. 并将该方法用于1999年9月21日台湾集集地震的再定位,其结果与其他方法相比,SAMS方法不仅降低了发震时刻与震源深度间的折衷关系对定位结果的影响,而且其定位结果具有很高的稳定性和分辨率. 相似文献
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由共成像点道集抽取的共偏移距道集可以当成相同地下成像的多次观测.由于偏移误差的影响,在不同共偏移距道集上,同一采样点存在水平和垂直方向上的错位.本文提出一种基于地震图像校准的共成像点道集增强技术,实现了不同偏移距道集在时间和空间上的逐点匹配对齐.在本文中以2D局部归一化互相关来表征共偏移距道集和叠加道集在相同时空位置的相似度,假设在不同水平和垂直移动量时的互相关满足连续凸函数,利用求导方法估计共偏移距道集在该位置处的非整数校正量,最后采用双线性内插方法估计成像振幅.传统道集拉平技术在垂直方向进行校正量消除,本文方法能有效估计共偏移距道集中的水平和垂直校正量,并在亚像素域估计正确的成像振幅.模型数据和实际数据的处理结果表明,本文方法能有效增强共成像点道集中同相轴的一致性,提高叠加结果的分辨率. 相似文献
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采用双差定位方法对2012年6月24日宁蒗-盐源MS5.7地震主震及其余震序列进行了重新定位. 首先采用时间域互相关技术对波形数据进行处理, 获得高精度的事件对走时差; 然后分别使用目录数据、 波形互相关数据和目录数据+波形互相关数据等3种不同的数据组合, 对宁蒗-盐源MS5.7地震主震及其余震序列进行重新定位. 3种数据组合的主震定位结果、 参与重定位的地震事件数、 最终被定位的地震事件数及重定位结果标准差等对比结果表明, 同时使用目录数据和波形互相关数据所获得的重定位结果最佳. 重定位结果显示, 宁蒗-盐源MS5.7地震主震的震中位置为(27.790°N、 100.707°E), 震源深度为10.4 km, 发震时刻为北京时间2012年6月24日15时59分32.74秒. 本文结果表明, 震源区附近NW走向的永宁断裂为宁蒗-盐源MS5.7地震的发震构造. 相似文献
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W. Cao S. M. Hanafy G. T. Schuster G. Zhan C. Boonyasiriwat 《Geophysical Prospecting》2012,60(1):1-17
Time reversal mirrors can be used to backpropagate and refocus incident wavefields to their actual source location, with the subsequent benefits of imaging with high‐resolution and super‐stacking properties. These benefits of time reversal mirrors have been previously verified with computer simulations and laboratory experiments but not with exploration‐scale seismic data. We now demonstrate the high‐resolution and the super‐stacking properties in locating seismic sources with field seismic data that include multiple scattering. Tests on both synthetic data and field data show that a time reversal mirror has the potential to exceed the Rayleigh resolution limit by factors of 4 or more. Results also show that a time reversal mirror has a significant resilience to strong Gaussian noise and that accurate imaging of source locations from passive seismic data can be accomplished with traces having signal‐to‐noise ratios as low as 0.001. Synthetic tests also demonstrate that time reversal mirrors can sometimes enhance the signal by a factor proportional to the square root of the product of the number of traces, denoted as N and the number of events in the traces. This enhancement property is denoted as super‐stacking and greatly exceeds the classical signal‐to‐noise enhancement factor of . High‐resolution and super‐stacking are properties also enjoyed by seismic interferometry and reverse‐time migration with the exact velocity model. 相似文献
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共反射面元（Common Reflection Surface）叠加是一种独立于宏观速度模型的零偏移距剖面成像方法,传统的CRS叠加实现是以数据驱动的方式对属性参数进行自动搜索并对其进行优化合成相应的CRS叠加算子,通过该算子进行叠加能够得到信噪比和连续性更高的零偏移距剖面.但是数据驱动的实现方式带来了不可避免的“倾角歧视现象”,它造成了弱有效反射信号损失和运动学特征失真的问题.本文提出的倾角分解CRS叠加方法成功解决了上述问题,使CRS叠加方法更具实用价值. 相似文献
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Roberto de Franco 《Geophysical Prospecting》2005,53(3):335-348
Multi‐refractor imaging is a technique for constructing a single two‐dimensional image of a number of refractors by stacking multiple convolved and cross‐correlated reversed shot records. The method is most effective with high‐fold data that have been obtained with roll‐along acquisition programs because the stacking process significantly improves the signal‐to‐noise ratios. The major advantage of the multi‐refractor imaging method is that all the data can be stacked to maximize the signal‐to‐noise ratios before the measurement of any traveltimes. However, the signal‐to‐noise ratios can be further increased if only those traces that have arrivals from the same refractor are used, and if the correct reciprocal times or traces are employed. A field case study shows that multi‐refractor imaging can produce a cross‐section similar to the familiar reflection cross‐section with substantially higher signal‐to‐noise ratios for the equivalent interfaces. 相似文献
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Flavio Poletto Biancamaria Farina Gualtiero Böhm Kees Wapenaar 《Geophysical Prospecting》2015,63(3):567-586
We present a modified interferometry method based on local tangent‐phase analysis, which corrects the cross‐correlated data before summation. The approach makes it possible to synthesize virtual signals usually vanishing in the conventional seismic interferometry summation. For a given pair of receivers and a set of different source positions, a plurality of virtual traces is obtained at new stationary projected points located along the signal wavefronts passing through the real reference receiver. The position of the projected points is estimated by minimizing travel times using wavefront constraint and correlation‐signal tangent information. The method uses mixed processing, which is partially based on velocity‐model knowledge and on data‐based blind interferometry. The approach can be used for selected events, including reflections with different stationary conditions and projected points with respect to those of the direct arrivals, to extend the interferometry representation in seismic exploration data where conventional illumination coverage is not sufficient to obtain the stationary‐phase condition. We discuss possible applications in crosswell geometry with a velocity anomaly and a time lapse. 相似文献
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Jürgen Mann Rainer Jger Thilo Müller German Hcht Peter Hubral 《Journal of Applied Geophysics》1999,42(3-4)
The simulation of a zero-offset (ZO) stack section from multi-coverage reflection data is a standard imaging method in seismic processing. It significantly reduces the amount of data and increases the signal-to-noise ratio due to constructive interference of correlated events. Conventional imaging methods, e.g., normal moveout (NMO)/dip moveout (DMO)/stack or pre-stack migration, require a sufficiently accurate macro-velocity model to yield appropriate results, whereas the recently introduced common-reflection-surface stack does not depend on a macro-velocity model. For two-dimensional seismic acquisition, its stacking operator depends on three wavefield attributes and approximates the kinematic multi-coverage reflection response of curved interfaces in laterally inhomogeneous media. The common-reflection-surface stack moveout formula defines a stacking surface for each particular sample in the ZO section to be simulated. The stacking surfaces that fit best to actual events in the multi-coverage data set are determined by means of coherency analysis. In this way, we obtain a coherency section and a section of each of the three wavefield attributes defining the stacking operator. These wavefield attributes characterize the curved interfaces and, thus, can be used for a subsequent inversion. In this paper, we focus on an application to a real land data set acquired over a salt dome. We propose three separate one-parametric search and coherency analyses to determine initial common-reflection-surface stack parameters. Optionally, a subsequent optimization algorithm can be performed to refine these initial parameters. The simulated ZO section obtained by the common-reflection-surface stack is compared to the result of a conventional NMO/DMO/stack processing sequence. We observe an increased signal-to-noise ratio and an improved continuity along the events for our proposed method — without loss of lateral resolution. 相似文献
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在地震勘探中,地形起伏和近地表速度的剧烈变化会导致地震波旅行时的扰动,通常会通过折射波信息来估算和消除这些扰动.本文在虚折射的基础上提出了逆虚折射干涉法,通过虚折射波场和原始折射波场的互相关,并对所有位于固定相位点上的检波点进行叠加,重构出逆虚折射波场.通过逆虚折射与超级虚折射的叠加,保证了不同偏移距下折射波振幅恢复的一致性,显著提高折射波的信噪比,有效提取弱信号.同时,本文采用反褶积干涉法来压制由于互相关和褶积产生的子波旁瓣的影响,弥补低频和高频能量的损失,改善恢复的折射波场的稳定性和分辨率.该新方法不需要知道近地表复杂速度模型的信息,可以将虚折射的勘探孔径恢复到原始地震记录的最大孔径.合成资料和实际资料的计算结果表明,基于反褶积的逆虚折射干涉法能够从低信噪比的资料中,有效恢复出折射波信息. 相似文献
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We apply interferometric theory to solve a three‐dimensional seismic residual statics problem to improve reflection imaging. The approach calculates the static solutions without picking the first arrivals from the shot or receiver gathers. The static correction accuracy can be significantly improved by utilising stacked virtual refraction gathers in the calculations. Shots and receivers may be placed at any position in a three‐dimensional seismic land survey. Therefore, it is difficult to determine stationary shots and receivers to form the virtual refraction traces that have identical arrival times, as in a two‐dimensional scenario. To overcome this problem, we use a three‐dimensional super‐virtual interferometry method for residual static calculations. The virtual refraction for a stationary shot/receiver pair is obtained via an integral along the receiver/shot lines, which does not require knowledge of the stationary locations. We pick the maximum energy times on the interferometric stacks and solve a set of linear equations to derive reliable residual static solutions. We further apply the approach to both synthetic and real data. 相似文献
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Least squares migration can eliminate the artifacts introduced by the direct imaging of irregular seismic data but is computationally costly and of slow convergence. In order to suppress the migration noise, we propose the preconditioned prestack plane-wave least squares reverse time migration (PLSRTM) method with singular spectrum constraint. Singular spectrum analysis (SSA) is used in the preconditioning of the take-offangle-domain common-image gathers (TADCIGs). In addition, we adopt randomized singular value decomposition (RSVD) to calculate the singular values. RSVD reduces the computational cost of SSA by replacing the singular value decomposition (SVD) of one large matrix with the SVD of two small matrices. We incorporate a regularization term into the preconditioned PLSRTM method that penalizes misfits between the migration images from the plane waves with adjacent angles to reduce the migration noise because the stacking of the migration results cannot effectively suppress the migration noise when the migration velocity contains errors. The regularization imposes smoothness constraints on the TADCIGs that favor differential semblance optimization constraints. Numerical analysis of synthetic data using the Marmousi model suggests that the proposed method can efficiently suppress the artifacts introduced by plane-wave gathers or irregular seismic data and improve the imaging quality of PLSRTM. Furthermore, it produces better images with less noise and more continuous structures even for inaccurate migration velocities. 相似文献
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Stéphane Rondenay 《Surveys in Geophysics》2009,30(4-5):377-405
This paper provides a review of array-based imaging techniques that use converted and scattered teleseismic waves. It addresses various aspects of the imaging process, from the preprocessing of the data to the application of the imaging algorithms. The reviewed techniques form a continuum with respect to the level of complexity adopted in the treatment of the scattering problem. On one end of the spectrum, images may be produced by simple stacking of normalized P-to-S conversion records (i.e., receiver functions), which are binned according to station or common conversion points (CCP) and mapped to depth. Finer resolution can be achieved through the stacking of singly scattered wavefields along diffraction hyperbolae to recover relative scattering intensity/potential at individual points through a 2-D or 3-D model space. Moving to higher levels of complexity, we find methods that involve inversion/backprojection of scattered teleseismic wavefield to recover estimates of localized material property perturbations with respect to an a priori background model. 相似文献