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191.
Inversion of potential field data using the structural index as weighting function rate decay 总被引:1,自引:0,他引:1
Nonparametric inverse methods provide a general framework for solving potential‐field problems. The use of weighted norms leads to a general regularization problem of Tikhonov form. We present an alternative procedure to estimate the source susceptibility distribution from potential field measurements exploiting inversion methods by means of a flexible depth‐weighting function in the Tikhonov formulation. Our approach improves the formulation proposed by Li and Oldenburg (1996, 1998) , differing significantly in the definition of the depth‐weighting function. In our formalism the depth weighting function is associated not to the field decay of a single block (which can be representative of just a part of the source) but to the field decay of the whole source, thus implying that the data inversion is independent on the cell shape. So, in our procedure, the depth‐weighting function is not given with a fixed exponent but with the structural index N of the source as the exponent. Differently than previous methods, our choice gives a substantial objectivity to the form of the depth‐weighting function and to the consequent solutions. The allowed values for the exponent of the depth‐weighting function depend on the range of N for sources: 0 ≤N≤ 3 (magnetic case). The analysis regarding the cases of simple sources such as dipoles, dipole lines, dykes or contacts, validate our hypothesis. The study of a complex synthetic case also proves that the depth‐weighting decay cannot be necessarily assumed as equal to 3. Moreover it should not be kept constant for multi‐source models but should instead depend on the structural indices of the different sources. In this way we are able to successfully invert the magnetic data of the Vulture area, Southern Italy. An original aspect of the proposed inversion scheme is that it brings an explicit link between two widely used types of interpretation methods, namely those assuming homogeneous fields, such as Euler deconvolution or depth from extreme points transformation and the inversion under the Tikhonov‐form including a depth‐weighting function. The availability of further constraints, from drillings or known geology, will definitely improve the quality of the solution. 相似文献
192.
PAUL BENJAMIN CRILLY 《地理学报(英文版)》1990,(4)
The use of a cross-correlation prefiltering technique to enhance the ability of Jansson's iterativedeconvolution procedure to deconvolve extremely noisy chromatographic data is investigated.Test casesinclude peaks whose resolutions are as low as 0.35 and whose signal-to-noise ratios are as low as 1:1.Evaluation criteria include RMS error,relative peak error and peak area repeatability.For comparisonpurposes,relative peak area errors and peak area variances are also evaluated for noisy but well resolvedpeaks that have only been prefiltered with the cross-correlation filter.Jansson's method in conjunctionwith cross-correlation prefiltering is shown not only to resolve overlapped peaks but in some cases toimprove their signal-to-noise ratios.The study also establishes some limits to the capabilities of Jansson'smethod will regard to adverse data conditions. 相似文献
193.
194.
利用伴随算子L*,直接的偏移方法通常导致一个低分辨率或模糊的地震成像.线性化偏移反演方法需求解一个最小二乘问题.但直接的最小二乘方法的数值不稳定,为目视解译带来困难.本文建立约束正则化数学模型,研究了地震偏移反演成像问题的迭代正则化求解方法.首先对最小二乘问题施加正则化约束,接着利用梯度迭代法求解反演成像问题,特别是提出了共轭梯度方法的混合实现技巧.为了表征该方法的可实际利用性,分别对一维,二维和三维地震模型进行了数值模拟.结果表明该正则偏移反演成像方法是有效的,对于实际的地震成像问题有着良好的应用前景. 相似文献
195.
196.
基于水库气枪震源数据的频域水准比例因子反褶积方法分析 总被引:1,自引:0,他引:1
基于2016年福建南一水库气枪实验资料,利用频率域水准因子反褶积方法和互相关时延检测技术,研究水准比例因子及台站的背景噪声水平对反褶积计算结果的影响,并对反褶积法消除不同枪压引起的震源影响效果进行分析。结果表明:(1)水准比例因子越小,反褶积计算后的波形信噪比越小,当水准比例因子取值过小时,走时识别误差较大;(2)台站气枪记录的信噪比越大,走时识别精度越高,参考台记录的信噪比对结果的影响远大于远场台,当远场台记录的信噪比大于10时,走时误差一般小于6ms,而当参考台记录的信噪比为30左右时,走时误差可能达到20ms;(3)气枪震源差异较大时,频域水准反褶积方法去除震源效应的效果较好,而在震源差异较小时,可能引入方法误差。 相似文献
197.
198.
地震子波在叠前时间偏移前、偏移过程中以及偏移后具有不同特性和非稳态性,使得基于子波压缩原理的反褶积和基于绕射叠加原理的叠前时间偏移不能有效地提高薄互层地震分辨率.本文基于叠前时间偏移前后以及偏移过程中地震子波频率特性的分析,联合三种高分辨率处理方法对薄互层进行成像,即偏移前CMP道集应用反Q滤波补偿高频衰减、偏移过程中应用最优加权Kirchhoff叠前时间偏移降低高频损失、偏移后在CRP道集上应用子波调谐反褶积拓展频带.数值分析和实例证明,本文采用的三种高分辨率处理方法是必要的,对刻画薄互层厚度与边界能够取得好的效果,利于后续的岩性储层预测与AVO/AVP/AVA反演. 相似文献
199.
波阻抗处理技术研究及应用 总被引:2,自引:0,他引:2
文中论述了波阻抗处理技术及直接用于地质解释的绝对波抗剖面产生过程,并指出,若测区无测井数据,可应用震道积分技术,求取相对波阻抗剖面,也有助于地质解释。 相似文献
200.
Xuanhui Yang Yu Jeffrey Gu Ping Shen Xiqiang Liu Zhizhen Zheng 《Pure and Applied Geophysics》2006,163(8):1515-1536
Signal extraction from overlapping seismic records is a common problem in geophysical data analysis. Identification and separation
of multiple seismic arrivals, analysis of large earthquakes as multiple point sources, and calculation of the true yield of
a large nuclear explosion from interfering small explosion, all hinge on our ability to effectively decouple two interfering
wave signals. This paper presents a method for signal separation based on an adaptive filtering technique. We apply a semi-deconvolution
algorithm to overlapping explosion records and S/SKS phase groups, and then perform noise reduction and signal decoupling
under different a priori conditions and assess the stabilities using a variance reduction approach. We demonstrate, through numerical experiments
and analysis of seismic station records, that the adaptive method can be both robust and practical for regional and teleseismic
applications. 相似文献