基于正则化理论的时频分析方法及应用
A regularization theory-based method for time-frequency analysis and its applications
第一作者:
责任编辑: 叶佩
收稿日期: 2022-07-22 修回日期: 2023-02-1
基金资助: |
|
Received: 2022-07-22 Revised: 2023-02-1
时频分析方法在地震勘探中有广泛的应用,因而获得具有良好时频分辨率的时频分析算法至关重要。传统的时频分析方法存在着一定的局限性,为克服这些局限性,提出了基于正则化理论的时频分析方法。该方法认为,短时窗信号是不同频率谐波的叠加,应从求解反问题的角度考察时频分析问题。在此视角下,时频分析问题具有不适定性,为得到有意义的时频谱,需要在正则化理论框架下进行时频分析。考察了正则化理论中常用的L1范数约束、L2范数约束以及最小支撑约束条件下的求解方法,并将3种约束函数的求解方法统一到同一个求解框架中。通过数值分析表明,最小支撑约束的时频分析方法具有较高的时频分辨率。将方法系统应用于一个特定研究区的实际资料,获得了具有较高时频分辨率的时频数据体,并利用单频数据体清晰刻画了储层的平面展布范围,展示了方法良好的应用前景。
关键词:
Time-frequency analysis (TFA) has been widely used in seismic exploration,thus it is crucial to develop a TFA algorithm with high time-frequency resolution.Given the limitations of conventional TFA methods,this study proposed a TFA method based on the regularization theory.The proposed method considers the signal in a short-time window as a superposition of harmonics with different frequencies and takes the TFA problem as an inverse problem.From this perspective,the TFA problem is ill-posed and needs to be solved based on the regularization theory to get a significant time-frequency spectrum.The solution methods under the conditions of L1 and L2 norm constraints and the minimum support constraint are commonly used in the regularization theory.This study investigated these solution methods and unified them into the same solution framework.Numerical analysis shows that the TFA method under the condition of the minimum support constraint yielded high time-frequency resolution.This method was systematically applied to the actual data of a specific study area,producing a time-frequency data volume with high time-frequency resolution.Moreover,the planar reservoir distribution was clearly characterized using a single-frequency data volume,demonstrating the promising application prospect of the method.
Keywords:
本文引用格式
张金强.
ZHANG Jin-Qiang.
0 引言
地球物理领域常用的时频分析方法主要有短时傅里叶变换、连续小波变换、S变换及广义S变换、WVD、Hilbert-Huang变换以及匹配追踪等,这些方法各有其特点和局限。短时傅里叶变换、连续小波变换以及S变换都是线性时频分析方法[10-11],都需要对时间信号加窗截断得到局部信号,从而获得不同时间局部的频域特征[12-13]。这类方法尽管时频聚集特性不同(小波变换及S变换较短视窗傅里叶变换具有更好的时频聚集特性),但是都会受到海森伯格测不准原理的约束。WVD(Wigner-Ville 分布)具有较高的时频分辨率,但是要受到交叉项的影响[14-15],导致其应用局限。Hilbert-Huang变换(HHT)是基于经验模态分解的方法,具有较高的时频聚焦特性,但是也存在模态混叠等问题[16]。匹配追踪方法(MP)通过建立完备的时频信号字典,利用反复迭代寻求以最少时频原子获得信号的最佳匹配[17-18]。这种方法由于采用稀疏表示技术,通常可以获得比连续小波变换和Gabor变换更好的时频分辨率,但是由于其本身遍历性的迭代算法,计算成本较高。
1 方法原理
在传统的离散傅里叶变换理论中,有限离散信号与其离散谱之间存在以下关系:
式中:
式(1)和式(2)可表达为矩阵形式:
x=
式中:X=
设离散短时窗信号为d,根据傅里叶变换的基本理论,d可以由不同频率的谐波叠加而得到,参照式(2):
式中:
所表征的为同一时刻不同频率谐波的函数值。核矩阵的第m列对应的列向量为:
所表征的为同一频率谐波不同时刻的函数值。F矩阵的维度为L×M,L为短时窗信号的样点数,M为不同频率谐波的个数,根据具体问题确定有意义的频带范围和频率采样间隔,最终确定M。m=
取得最小值。其中
表征的是利用估计频谱得到离散信号与实测信号的偏差。S(m)为约束函数,α为决定约束函数贡献大小的平衡参数,α越大约束函数的贡献越大。选择不同的约束函数,得到的解也不同。常用的约束函数有
尽管约束函数有多种形式,但多数约束函数可以从形式上表示为某个函数的L2范数形式,即
对于式(8)有
按照以上表述,更进一步,可以将约束函数表示为
对照式(11)和式(9)有
对照式(11)和式(10)有
这样,式(5)可以表示为
式(14)用矩阵的形式表示为
对应于式(6)、(7)、(8)的约束函数的矩阵形式分别为
式(15)可以进一步变换为如下形式:
令: , = ,
最终将式(5)变换为如下形式:
式(20)与经典的带正则化项的最小二乘问题形式上完全一致,所不同是Fw是与m有关的矩阵,因此需要进行迭代求解。以使用式(8)作为约束函数的情况说明迭代过程。
首先,注意到采用常规L2范数(即式7)作为约束函数时,We=I,此时可以用常规最小二乘得到问题的解:
可以用式(21)作为问题的初始解
利用更新的m后,进入到下一个迭代过程,重复计算We,直至再次更新m。上述循环的终止原则可以选择使式(5)值趋于稳定,也可以根据经验选择合适的迭代次数。
上述过程得到一个短时窗信号的高分辨率频谱,实际应用中,我们应用一个窗函数对地震道进行逐点滑动,这样就可以得到整个地震道的时频谱。窗函数可以选择汉宁窗函数,由于汉宁窗函数具有由中心点向两端迅速衰减的特征,所以我们估算的其实是中心点附近数据的频谱。算法的这种特征,要求将时窗中心点作为时间零点,因此核矩阵应按此进行调整。
对于地震道时频分析,可以先将地震道进行希尔伯特变换,得到对应的复地震道,在此基础上进行相应的时频分析。
2 数值算例
设计一个由两个单频信号叠加而成的信号:
图1
图1
两个单频信号的合成信号
a—20 Hz正弦信号;b—50 Hz正弦信号;c—
Fig.1
Synthetic signal of the two sinuasoidal signals
a—sinuasoidal signal of 20 Hz;b—sinuasoidal signal of 50 Hz;c—summary signal of
图2
图2
不同时频分析方法得到时频谱对比
a—CWT时频谱;b—RL2TFS时频谱;c—RL1TFS时频谱;d—RMSTFS时频谱
Fig.2
Comparisons of time-frequency spectrum of different time frequency analysis method
a—time-frequency spectrum of CWT;b—time-frequency spectrum of RL2TFS;c—time-frequency spectrum of RL1TFS;d—time-frequency spectrum of RMSTFS
通过实验分析可以看出,最小支撑约束稀疏谱算法具有较L1范数约束和L2范数约束的算法更好的时频分辨率。因此重点对此方法进行进一步研究。为进一步说明最小支撑约束稀疏谱算法对短时窗信号的频谱的分辨能力,研究不同长度时窗条件下算法估算频谱的精度,设计如下算例。雷克子波是地震勘探中经常用到的子波,该子波有理论频谱,便于研究。因此我们使用不同长度的汉宁窗对雷克子波进行截断,比较短时傅里叶变换与最小支撑约束稀疏谱算法得到的频谱。首先,我们用长度为40 ms的汉宁窗截断雷克子波,研究两种算法得到的频谱(图3),然后用长度为20 ms的汉宁窗截断雷克子波,研究其频谱(图4)。在进行短时傅里叶变换时,为得到高精度频谱,同样以汉宁窗截断信号,将短时窗信号外数据充零并延长数据长度至1 024 ms。对比图3与图4可以看出,首先最小支撑约束稀疏谱较之传统的短时傅里叶变换的频谱更为接近雷克子波的理论频谱,其次,当汉宁窗的长度为40 ms时,短时傅里叶变换的频谱形态与理论谱虽有较大差异,但在高频段仍有一定的符合度,当汉宁窗的长度变为20 ms时,短时傅里叶变换的频谱已经完全不能反映雷克子波的频谱特征了,最小支撑约束稀疏谱虽然与理论谱的差异增大,但仍可以较好地拟合雷克子波的理论频谱。另外,图3c及图4c中都可以看到利用复地震道为输入的最小支撑约束频谱(红色曲线)较以原始地震道为输入的最小支撑约束频谱(藏青色曲线)更接近于雷克子波的理论曲线。在汉宁窗长度为40 ms时,二者整体比较接近,当汉宁窗长度为20 ms时,利用复地震道作为输入的最小支撑约束频谱明显地优于利用原始地震道作为输入的结果。这主要是因为,复地震道虚部相当于对原始地震道作了90°相移,增加了数据冗余,同时复谐波的实部与虚部也呈90°相移,这样利用复地震道反演频谱增加了反演的稳定性和精度。
图3
图3
40 ms汉宁窗作用于雷克子波得到的信号及其对应的频谱
a—40 ms汉宁窗函数及雷克子波叠合;b—汉宁窗作用于雷克子波得到信号;c—不同时频分析方法计算
Fig.3
40 ms Hanning function applied on the ricker wavelet and the correpsonding spectrum
a—40 ms Hanning function and Riker wavelet;b—signal obtained by applying Hanning on ricker wavelet;c—frequency spectrum of the signal (
图4
图4
20 ms汉宁窗作用于雷克子波得到的信号及其对应的频谱
a—20 ms汉宁窗函数及雷克子波叠合;b—汉宁窗作用于雷克子波得到信号;c—不同时频分析方法计算的
Fig.4
20 ms Hanning function applied on the ricker wavelet and the correpsonding spectrum
a—20 ms Hanning function and Riker Wavelet;b—signal obtained by applying Hanning on ricker wavelet;c—frequency spectrum of the signal(
图5
图5
顶底反射系数相同不同时间厚度地层的合成地震记录及不同算法计算的时频谱
a—地震反射系数序列;b—合成地震道;c—CWT时频谱;d—RMSTFS时频谱
Fig.5
Synthetic record of different thikness layers with same recflction coefficient on top and bottom and the corresponding time-frequency spectrum
a—seismic reflection series;b—synthetic record;c—spectrum of CWT;d—spectrum of RMSTFS
图6
图6
顶底反射系数相反不同时间厚度地层的合成地震记录及不同算法计算的时频谱
a—地震反射系数序列;b—合成地震道;c—CWT时频谱;d—RMSTFS时频谱
Fig.6
Synthetic record of different thikness layers with revese recflction coefficients on top and bottom and the corresponding time-frequency spectrum
a—seismic reflection series;b—synthetic record;c—spectrum of CWT;d—spectrum of RMSTFS
对比两个算例的结果,可以看出:连续小波变换的频谱在低频段的时间分辨率低,有明显的自上而下的条纹,是明显的假象。最小支撑约束的时频谱得到的结果显示时频分辨率更高,时频谱能量团聚焦清晰,主能量团时间跨度普遍小于连续小波变换时频谱上对应主能量团的时间跨度,说明方法具有较好的时间分辨率。在图5d中,反射系数对的时间厚度为12 ms时反射的顶底清晰可分,并且在此之后,反射顶底之间频谱显示出调谐作用造成的陷波点随着时间厚度的增大有规律地向低频偏移的现象。连续小波变换的频谱也表现出类似的现象,但其能量团聚焦差,与地层反射的顶底对应关系差。
对比两个算例还可以发现,当反射系数对大小相同符号相同时,时频谱的分辨率更高,其调谐作用的陷波点偏向低频段,因而也更为明显。为更清楚地解释此现象,计算了两种反射系数对在不同厚度条件下调谐作用滤波器的频率响应曲线,如图7所示。当反射系数对大小相同、符号相反时,厚度为16 ms时第一个陷波点为62.5 Hz,由于地震子波本身的频带范围限制,不能清晰观察。当厚度增加到24 ms时,第一个陷波点为41.67 Hz,在时频谱上可以清晰观察。对于大小相等、符号相反的反射系数对,当厚度为16 ms时,陷波点即在地震频带内,可以清晰观察。
图7
图7
不同厚度反射系数对调谐滤波器的响应曲线
a—
Fig.7
The frequency response curves of reflection pairs with different time thickness
a—the frequency response curves for reflection paris of
将时间信号变换到时频域这个过程必然是具有多解性的,对于一些简单的算例,如上文中所设计的算例,我们可以通过理论分析的方法清楚地获知其理论时频谱的特征,因而易于识别哪些现象是地层本身的反映,哪些现象是算法的假象,而对于现实中更为复杂的时间信号,则往往难以判定,因此也更要求算法能够捕获信号中地层的响应特征。通过数据实验算例可以看出,在正则化理论框架下,利用最小支撑约束条件求解的最小支撑稀疏时频谱具有良好的时频谱特征,在时频域都具有良好的分辨能力,同时可以清楚地展现地层的调谐、陷波作用的基本特征,是一种非常有应用潜力的时频分析方法。通过实验算例分析,也启示我们:由于地层反射波的时频谱存在谐振区(振幅极大值)和陷频区(振幅极小值),因此,在时频域振幅分析时,需根据地震数据的频率范围和地层厚度变化范围合理选取时频分析的频率范围;从另一方面说,选择了某一频率得到的时频剖面,对其振幅的变化的分析和解释也应注意谐振区和陷频区的影响。
3 实际资料应用
方法在鄂尔多斯盆地西缘某工区进行了系统应用。该区以侏罗系延安组为主要目的层,储层为河流—三角洲沉积,河道砂体横向变化快,预测困难。应用Partyka等[25]提出的做法,首先对地震道进行时频分解,然后将抽取不同频率对应的能谱值形成单频数据体。图8为利用连续小波变换和最小支撑约束稀疏时频分析得到的不同频率的能谱剖面。从这些剖面可以看出,在低频段,如10 Hz和20 Hz的能谱剖面,连续小波变换得到能谱剖面时间分辨率低,在剖面上部缺失有意义的低频信号,10 Hz的能谱剖面尤为明显,而最小支撑约束稀疏时频分析得到的能谱剖面则在剖面的不同部位都呈现出有意义的信号。在高频信号段,如60 Hz,两种方法得到的能谱剖面相似度较高,最小支撑约束稀疏时频分析得到能谱剖面的时间分辨率仍优于连续小波变换。对10 Hz的低频能谱剖面进行局部放大,如图9所示。在图9b的能谱剖面的红色椭圆内的高能谱值反映了工区内主要目的层的储层响应,而在连续小波变换的对应剖面上则没有类似的异常响应。
图8
图8
连续小波变换和最小支撑约束稀疏谱得到不同频率的能谱剖面
a—连续小波变换10 Hz能谱剖面;b—RMSTFS 10 Hz能谱剖面;c—连续小波变换20 Hz能谱剖面;d—RMSTFS 20 Hz能谱剖面;e—连续小波变换60 Hz能谱剖面;f—RMSTFS 60 Hz能谱剖面
Fig.8
Sections of different frequency spectrum obtained by CWT and RMSTFS
a—section of 10 Hz spectral spectrum of CWT;b—section of 10 Hz spectral spectrum of RMSTFS;c—section of 20 Hz spectral spectrum of CWT;d—section of 20 Hz spectral spectrum of RMSTFS;e—section of 60 Hz spectral spectrum of CWT;f—section of 60 Hz spectral spectrum of RMSTFS
图9
图9
连续小波变换及最小支撑约束稀疏时频分析得到10 Hz能谱剖面对比
a—连续小波变换10 Hz能谱剖面(局部放大);b—最小支撑约束时频分析10 Hz能谱剖面(局部放大)
Fig.9
Comparisons of 10 Hz spectrum section obtained by CWT and RMSTFS
a—section of 10 Hz spectral spectrum of CWT(zoomed);b—section of 10 Hz spectral spectrum of RMSTFS(zoomed)
图10
图10
不同算法计算的能谱沿层切片
a—连续小波变换10 Hz能谱沿层切片;b—最小支撑约束时频分析10 Hz能谱沿层切片
Fig.10
Horizon slices of 10 Hz spectrum by different algorithms
a—Horizon slice of 10 Hz CWT spectrum;b—Horizon slice of 10 Hz RMSTFS spectrum
4 结论
利用求解反问题的思路考察时频分析问题,时频分析问题可以描述为正则化理论框架下的反问题。不同的正则化约束函数约束下的时频谱求解可以统一到同一个求解框架。数值计算结果表明,最小支撑约束的时频分析方法具有最佳的时频分辨率。方法在特定研究区的应用显示了良好的时频分析方法有助于凸显储层的地震响应,在地震储层预测中具有较好的应用前景。
方法通过迭代求解信号的时频谱,运算量较大。因此,算法在运算效率的提高上有待进一步研究。
参考文献
高分辨率地震资料处理技术综述
[J]. ,
A review of high-resolution seismic data processing approaches
[J]. ,
基于Curvelet域的叠前地震资料去噪方法
[J]. ,
Curvelet domain-based prestack seismic data denoise method
[J]. ,
基于S变换的随机噪声压制方法
[J]. ,
The method for attenuating random noise based on S transform
[J]. ,
时频域变分模态分解地震资料去噪方法
[J]. ,
Seismic data de-noising method on VMD in time-frequency domain
[J]. ,
时频域相位滤波在远震接收函数噪声压制中的应用
[J]. ,
The time frequency domain phase filter and its application in noise suppression of teleseismic receiver functions
[J]. ,
基于三参数小波的频谱分解方法
[J]. ,
Spectrum decomposition based on three-parameter wavelet
[J]. ,
分频道积分技术在苏59气田储层预测中的应用
[J]. ,
Application of frequency-shared trace integration technique to reservoir prediction in Su59 gas field
[J]. ,
同步挤压小波变换在储层预测中的应用研究
[J]. ,
Application research of synchrosqueezing wavelet transform in the reservoir prediction
[J]. ,
基于匹配追踪算法的高精度页岩气“甜点”识别
[J]. ,
High-precision seismic prediction of shale gas sweet spots based on matching pursuit algorithm
[J]. ,
线性时频分析方法综述
[J]. ,
Review on linear time frequency analysis methods
[J]. ,
三种线性时频分析方法的影响因素及精度分析
[J]. ,
The influential factors and accuracy of three time-freqency analyses
[J]. ,
Discrete Gabor transform
[J]. ,DOI:10.1109/78.224251 URL [本文引用: 1]
Instantaneous spectral attributes using scales in continuous-wavelet transform
[J]. ,DOI:10.1190/1.3054145 URL [本文引用: 1]
Instantaneous spectral properties of seismic data — center frequency, root-mean-square frequency, bandwidth — often are extracted from time-frequency spectra to describe frequency-dependent rock properties. These attributes are derived using definitions from probability theory. A time-frequency spectrum can be obtained from approaches such as short-time Fourier transform (STFT) or time-frequency continuous-wavelet transform (TFCWT). TFCWT does not require preselecting a time window, which is essential in STFT. The TFCWT method converts a scalogram (i.e., time-scale map) obtained from the continuous-wavelet transform (CWT) into a time-frequency map. However, our method includes mathematical formulas that compute the instantaneous spectral attributes from the scalogram (similar to those computed from the TFCWT), avoiding conversion into a time-frequency spectrum. Computation does not require a predefined window length because it is based on the CWT. This technique optimally decomposes a multiscale signal. For nonstationary signal analysis, spectral decomposition from [Formula: see text] has better time-frequency resolution than STFT, so the instantaneous spectral attributes from CWT are expected to be better than those from STFT.
基于Wigner-Ville分布于Chrip-Z变换的高分辨率时频分析方法
[J]. ,
A new high-resolution time-freqency method based on Wigner-Ville distribution and Chrip-Z transform
[J]. ,
基于分数阶Wigner-Ville分布的地震信号谱分解
[J]. ,
Spectral decomposition of seismic signals based on fractional Wigner-Ville distribution
[J]. ,
Empirical mode decomposetion for seismic time-freqency analysis
[J]. ,DOI:10.1190/geo2012-0199.1 URL [本文引用: 1]
Time-frequency analysis plays a significant role in seismic data processing and interpretation. Complete ensemble empirical mode decomposition decomposes a seismic signal into a sum of oscillatory components, with guaranteed positive and smoothly varying instantaneous frequencies. Analysis on synthetic and real data demonstrates that this method promises higher spectral-spatial resolution than the short-time Fourier transform or wavelet transform. Application on field data thus offers the potential of highlighting subtle geologic structures that might otherwise escape unnoticed.
Seismic time-frequency spectral decom-position by matching pursuit
[J]. ,DOI:10.1190/1.2387109 URL [本文引用: 1]
A seismic trace may be decomposed into a series of wavelets that match their time-frequency signature by using a matching pursuit algorithm, an iterative procedure of wavelet selection among a large and redundant dictionary. For reflection seismic signals, the Morlet wavelet may be employed, because it can represent quantitatively the energy attenuation and velocity dispersion of acoustic waves propagating through porous media. The efficiency of an adaptive wavelet selection is improved by making first a preliminary estimate and then a localized refining search, whereas complex-trace attributes and derived analytical expressions are also used in various stages. For a constituent wavelet, the scale is an important adaptive parameter that controls the width of wavelet in time and the bandwidth of the frequency spectrum. After matching pursuit decomposition, deleting wavelets with either very small or very large scale values can suppress spikes and sinusoid functions effectively from the time-frequency spectrum. This time-frequency spectrum may be used in turn for lithological analysis—for instance, detection of a gas reservoir. Investigation shows that the low-frequency shadow associated with a carbonate gas reservoir still exists, even high-frequency amplitudes are compensated by inverse-[Formula: see text] filtering.
Matching pursuit with time-freqency dictionaries
[J]. ,DOI:10.1109/78.258082 URL [本文引用: 1]
Constraint least-square spectral analysis:Application to seismic data
[J]. ,DOI:10.1190/geo2011-0210.1 URL [本文引用: 1]
An inversion-based algorithm for computing the time-frequency analysis of reflection seismograms using constrained least-squares spectral analysis is formulated and applied to modeled seismic waveforms and real seismic data. The Fourier series coefficients are computed as a function of time directly by inverting a basis of truncated sinusoidal kernels for a moving time window. The method resulted in spectra that have reduced window smearing for a given window length relative to the discrete Fourier transform irrespective of window shape, and a time-frequency analysis with a combination of time and frequency resolution that is superior to the short time Fourier transform and the continuous wavelet transform. The reduction in spectral smoothing enables better determination of the spectral characteristics of interfering reflections within a short window. The degree of resolution improvement relative to the short time Fourier transform increases as window length decreases. As compared with the continuous wavelet transform, the method has greatly improved temporal resolution, particularly at low frequencies.
最小二乘约束下的频谱分析技术及其应用
[J]. ,
Least square constraint time frequency method and its application
[J]. ,
稀疏短时傅里叶变换谱分解方法及应用
[J]. ,
Sparse shot-time Fourier transform spectral decomposition method and its application
[J]. ,
Seismic sparse-layer reflectivity inversion using basis pursuit decomposition
[J]. ,DOI:10.1190/geo2011-0103.1 URL [本文引用: 1]
A basis pursuit inversion of seismic reflection data for reflection coefficients is introduced as an alternative method of incorporating a priori information in the seismic inversion process. The inversion is accomplished by building a dictionary of functions representing reflectivity patterns and constituting the seismic trace as a superposition of these patterns. Basis pursuit decomposition finds a sparse number of reflection responses that sum to form the seismic trace. When the dictionary of functions is chosen to be a wedge-model of reflection coefficient pairs convolved with the seismic wavelet, the resulting reflectivity inversion is a sparse-layer inversion, rather than a sparse-spike inversion. Synthetic tests suggest that a sparse-layer inversion using basis pursuit can better resolve thin beds than a comparable sparse-spike inversion. Application to field data indicates that sparse-layer inversion results in the potentially improved detectability and resolution of some thin layers and reveals apparent stratigraphic features that are not readily seen on conventional seismic sections.
Focusing geophysical inversion images
[J]. ,DOI:10.1190/1.1444596 URL [本文引用: 1]
A critical problem in inversion of geophysical data is developing a stable inverse problem solution that can simultaneously resolve complicated geological structures. The traditional way to obtain a stable solution is based on maximum smoothness criteria. This approach, however, provides smoothed unfocused images of real geoelectrical structures. Recently, a new approach to reconstruction of images has been developed based on a total variational stabilizing functional. However, in geophysical applications it still produces distorted images. In this paper we develop a new technique to solve this problem which we call focusing inversion images. It is based on specially selected stabilizing functionals, called minimum gradient support (MGS) functionals, which minimize the area where strong model parameter variations and discontinuity occur. We demonstrate that the MGS functional, in combination with the penalization function, helps to generate clearer and more focused images for geological structures than conventional maximum smoothness or total variation functionals. The method has been successfully tested on synthetic models and applied to real gravity data.
3D magnetic inversion with data compression and image focusing
[J]. ,DOI:10.1190/1.1512749 URL [本文引用: 1]
We develop a method of 3‐D magnetic anomaly inversion based on traditional Tikhonov regularization theory. We use a minimum support stabilizing functional to generate a sharp, focused inverse image. An iterative inversion process is constructed in the space of weighted model parameters that accelerates the convergence and robustness of the method. The weighting functions are selected based on sensitivity analysis. To speed up the computations and to decrease the size of memory required, we use a compression technique based on cubic interpolation.
Interpretational aspects of spectral decomposition in reservoir characterization
[J]. ,DOI:10.1190/1.1438295 URL [本文引用: 1]
/
〈 | 〉 |