Structural complexity-guided predictive filtering

Random noise attenuation utilizing predictive filtering achieves great performance in denoising seismic data. Conventional predictive filtering methods are based on fixed filter operators and neglect the complexity of structures. In this way, the denoised data cannot meet the requirement of balancing the signal preservation and noise removal. In this study, we proposed a structural complexity-guided predictive filtering method that utilizes an adapted filter operator to adjust the changes of structural complexity. The proposed structural complexity-guided predictive filtering mainly consists of two stages. A slope field information is acquired according to plane-wave destruction to assess the structural complexity. In addition, an adaptive filter operator is obtained to denoise the seismic data according to the adaptive factor. Both synthetic data and real seismic profiles are employed to examine the denoising capacity and flexibility of the refined predictive filtering using adaptive lengths. The analysis of the predicted results shows that adaptive predictive filtering is powerful and has the ability to eliminate random noises with negligible distortions.     

基于匹配滤波的多次波压制方法研究

常规滤波方法对浅海多次波压制不能取得理想效果.通过改变模型表面边界条件,求解波动方程实现多情景地震数值模拟.利用自由边界条件模拟时获得含海平面强反射多次波地震记录,而利用吸收边界条件时得到理想条件下无多次波地震记录.对比分析多次波对有效地震信号的影响得到海平面强反射多次波改变了有效地震信号的振幅、频率和相位.利用归一化方法计算得到压制多次波滤波器算子,并作用于含海平面强反射多次波地震记录.叠加地震剖面对比分析表明,归一化滤波器算子较好的压制了地震记录中的多次波,提高地震资料分辨率.最后,根据多次波产生条件,给出了利用实际区域简化地质模型的地震数值模拟结果计算归一化滤波器算子的方法,从而利用该方法压制实际地震数据中多次波.     

ANALYSIS OF DIFFRACTION PATTERN FILTERING OF VARIABLY DENSITY AND VARIABLY AREA RECORDINGS

When a small, transparent replica of a seismic section is illuminated by a homogeneous beam of coherent, monochromatic parallel light a diffraction pattern is created that is representation of the double Fourier spectrum of the recorded seismic waves, i.e. their spectrum in terms of frequency, f, and apparent wave number, k. Masking selected parts of this diffraction pattern causes the spectrum to be filtered: the recomposition of the filtered spectrum then provides a filtered section. The ideal seismic section for this purpose would be a continuous variable density section obtained from recording made at every point of the seismic line. The light transmission coefficient (in terms of light amplitude) at each spot of the replica should be linearly related to the instantaneous seismic signal strength at the spot on the seismic section to which it refers. Unfortunately we cannot make recordings at every point of a seismic line and in our practically realisable recordings we have to be content with sampling in the direction of the location coordinate x. This means that with variable density recordings aliasing will be present and evident in the spectrum obtained in the direction of k; furthermore, the aliased spectrum is also multiplied by a sine function of k because the recording obtained at a given station is not presented on the seismic section as a single line along the time axis, but occupies the entire width of the trace. The diffraction patterns created by variable density recordings of dipping sine waves, including clipped recordings, and of the effect of dip filtering in such sections are discussed. The efficiency of dip rejection is shown to decrease with increasing dip. The diffraction pattern of a variable density recording is found to be characterised by a relationship between point pairs in the pattern. No such simple relationship has been found for the diffraction pattern of a variable area section; the spectra of such VAR sections belong to a very special class, because the amplitude transmission coefficient has only two values, viz. 0 and 1. Consequently, selective masking of the diffraction pattern of a VAR section may give rise to a filtered profile that does not look like a VAR section at all. General statements about the diffraction pattern of VAR sections are hard to give, because the transmission coefficient at a given point in the replica is not proportional to the signal level in the seismic section at the relevant point. In the case of VAR presentation of harmonic waves it was found that, as well as the aliasing effect in the k direction, higher harmonics of the frequency are also introduced. Some synthetic examples are given that show dip filtering to be less effective with VAR than with variable density recordings. Some arguments are advanced in favour of the opinion that high-pass filtering of VAR sections will have less success than low-pass filtering. This is demonstrated by two synthetic examples.     

EMD新技术在数字波形预处理中的初步应用

介绍了EMD技术,给出由该技术产生的固有模态函数重构数字地震波形信号处理中所用滤波器算法。然后利用该方法对实际波形信号进行了初步处理,处理结果表明,基于EMD的滤波技术具有许多其它分析手段所不具备的特点,是一种新的滤波方法,可用于数字地震波形信号的预处理。     

对地震转换波的数字滤波处理

本文讨论运用低通滤波、偏振滤波、频率加强滤波、相关滤波及迭加处理等数字滤波方法,对地震转换波测深资料进行数字处理的方法及效果.数字滤波处理结果在一定程度上提高了记录的信噪比,为准确地进行相位对比和震相识别提供了可靠基础.      

ADAPT系统中数字滤波及仿真分析的用户定制

数字滤波和地震计仿真在分析地震波形有着很广泛的应用。该文描述了常规滤波分析、高级滤波分析和仿真分析在Adapt系统中的实现，同时还列举了几个例子并说明了用户定制的效果。     

地震逆散射波场和算子的谱分解

本文对地震逆散射的研究,旨在于为抑制层间多次波和地震波场多重散射对一次反射干扰效应提供理论依据.这对薄互层地层滤波的高频恢复、保幅弹性反演、衍射地震勘探及海洋地震勘探中的干扰消除皆具重要意义.本文基于上下行波分解及弹性波互易定理,导出横向变速介质条件下线性预测算子的表达式和反射数据的广义谱分解方程. 文中先由上覆地层广义反射透射矩阵的元素定义线性预测算子,并将其表示成一系列单程波算子的线性组合,之后将横向变速介质条件下线性预测方程表达为反射数据与线性预测算子及其逆的乘积. 对该方程的求解可获得上覆地层的线性预测算子,从而可借以求出相应的反射透射算子. 本文先将水平层状介质条件下垂直入射的一维线性预测方程推广到斜入射的情况,以此为参照,导出横向非均匀介质条件下反射数据的地震逆散射广义谱分解方程.文中也揭示了单程波地震逆散射算子、反射透射算子的性态.本文还针对水平层状介质条件,给出斜入射的数值结果.     

多尺度形态学在地震去噪中的应用

In this paper, multi-scaled morphology is introduced into the digital processing domain for land seismic data. First, we describe the basic theory of multi-scaled morphology image decomposition of exploration seismic waves; second, we illustrate how to use multi-scaled morphology for seismic data processing using two real examples. The first example demonstrates suppressing the surface waves in pre-stack seismic records using multi-scaled morphology decomposition and reconstitution and the other example demonstrates filtering different interference waves on the seismic record. Multi-scaled morphology filtering separates signal from noise by the detailed differences of the wave shapes. The successful applications suggest that multi-scaled morphology has a promising application in seismic data processing.     

地震图数字化技术中的倾斜校正和波形分割

重点阐述了在对模拟地震图进行数字化处理过程中，利用图中水平线信息完成倾斜校正以及利用中值滤波增强信号、自适应提取信号的波形分割技术。     

A COMPARISON OF STATISTICAL AND DETERMINISTIC WIENER DECONVOLUTION OF DEEP-TOW SEISMIC DATA*

Wiener ‘spiking’ deconvolution of seismic traces in the absence of a known source wavelet relies upon the use of digital filters, which are optimum in a least-squares error sense only if the wavelet to be deconvolved is minimum phase. In the marine environment in particular this condition is frequently violated, since bubble pulse oscillations result in source signatures which deviate significantly from minimum phase. The degree to which the deconvolution is impaired by such violation is generally difficult to assess, since without a measured source signature there is no optimally deconvolved trace with which the spiked trace may be compared. A recently developed near-bottom seismic profiler used in conjunction with a surface air gun source produces traces which contain the far-field source signature as the first arrival. Knowledge of this characteristic wavelet permits the design of two-sided Wiener spiking and shaping filters which can be used to accurately deconvolve the remainder of the trace. In this paper the performance of such optimum-lag filters is compared with that of the zero-lag (one-sided) operators which can be evaluated from the reflected arrival sequence alone by assuming a minimum phase source wavelet. Results indicate that the use of zero-lag operators on traces containing non-minimum phase wavelets introduces significant quantities of noise energy into the seismic record. Signal to noise ratios may however be preserved or even increased during deconvolution by the use of optimum-lag spiking or shaping filters. A debubbling technique involving matched filtering of the trace with the source wavelet followed by optimum-lag Wiener deconvolution did not give a higher quality result than can be obtained simply by the application of a suitably chosen Wiener shaping filter. However, cross correlation of an optimum-lag spike filtered trace with the known ‘actual output’ of the filter when presented with the source signature is found to enhance signal-to-noise ratio whilst maintaining improved resolution.     

汶川大震前数字地震仪位移地脉动低频异常现象研究

选取了2008年4月25日至5月12日间的四川台网14个台宽频带地震仪记录到的地脉动波形资料,把速度波形做适当的数据校正和滤波处理后,经积分转换成位移波形.频谱分析结果表明:地震发生前存在低频异常颤动,地震前2～3天开始0.1～0.3Hz频段傅里叶谱幅值逐渐增大;各个台的位移振幅值逐渐增强.其中靠近龙门山断裂带的台站记录到的地脉动变化较明显.     

地震面波频散的数字计算——方法与试验

在108-乙型数字计算机上进行了地震面波频散处理方法的试验。包括:（1）参数固定的和可变的数值滤波;（2）测定群速度的“移动窗”和“多重滤波”技术;（3）测定相速度的互相关法。应用了快速傅氏变换计算两个台记录的地震面波的互相关函数。使用数字处理技术分析地震面波频散,除了提高计算速度和便于处理之外,还可扩大测量周期的范围至20-70秒,从此可作出对地壳参数性质的更可靠的测定。     

Differential calibration of seismometers for measurement of rotation and strain

A method of correcting the seismometers’ responses discrepancy for differential measurements of strains and rotations in the seismic far field is proposed. The method concerns differential calibration of the whole seismometers’ array by electric current. A model of corrective filtering of the obtained differential signals in the Z domain is given. Two methods of the filter parameters’ estimation are introduced; they are based on the seismometers response to the calibration. A practical test of the methods — an analysis of a recorded seismic event — is added. Significant reduction of differences between simultaneous seismic recordings was obtained, which is interpreted as cleaning of differential signal from spurious elements.     

首都圈数字地震台网的微震定位实验

新建成的首都圈数字地震台网由 10 7个数字地震台站组成 ,其地震监测和定位能力需要检验。此文主要目的是为评估首都圈数字地震台网的地震活动监测能力提供参考依据。在地震定位中 ,应充分发挥数字地震记录的优势 ,采用相应的数字地震记录处理技术 ,提高地震定位的可靠性和精度。采用滤波、偏振及台站扫描、震相追踪等数字技术 ,提高了震相识别的可靠性和精度 ,并用Geiger方法对 2 0 0 1年首都圈数字地震台网记录到的 7个网内及网缘微震 (ML<2 .0 )进行了精确定位 ,还通过对爆破的定位来检验程序和方法的可靠性和精度。结果表明 ,震中定位误差估计小于2km ,震源深度误差估计小于 3km     

Time‐frequency seismic data de‐noising

Marine seismic data are always affected by noise. An effective method to handle a broad range of noise problems is a time‐frequency de‐noising algorithm. In this paper we explain details regarding the implementation of such a method. Special emphasis is given to the choice of threshold values, where several different strategies are investigated. In addition we present a number of processing results where time‐frequency de‐noising has been successfully applied to attenuate noise resulting from swell, cavitation, strumming and seismic interference. Our seismic interference noise removal approach applies time‐frequency de‐noising on slowness gathers (τ?p domain). This processing trick represents a novel approach, which efficiently handles certain types of seismic interference noise that otherwise are difficult to attenuate. We show that time‐frequency de‐noising is an effective, amplitude preserving and robust tool that gives superior results compared to many other conventional de‐noising algorithms (for example frequency filtering, τ?p or fx‐prediction). As a background, some of the physical mechanisms responsible for the different types of noise are also explained. Such physical understanding is important because it can provide guidelines for future survey planning and for the actual processing.     

深地震反射剖面构造信息识别研究

随着我国深部探测计划的实施,近年来在中国大陆地区实施了多条深地震反射剖面,获得了大量揭示地壳上地幔精细结构的宝贵资料. 为了更充分地挖掘这些资料中所包含的深部构造信息,本文在研究和总结前人工作的基础上,提出一种快速识别深地震反射剖面构造格架的方法. 该方法通过数据预处理、强振幅提取、中值滤波、对象识别、连续性计算和连续性滤波实现对深地震反射剖面构造格架识别. 同时,该方法还可通过对象倾角计算对复杂区域进行属性分析.     

攀枝花数字地震台网建设的技术难点及其应对措施

攀枝花数字地震台网是一个采用全无线传输方式的地方台网。唯一可资利用的大黑山中继站电磁干扰强烈和部分子台传输路径条件差是该台网设计建设中最大的技术难点。避、滤、纠是在攀枝花台网设计建设中采取的三大应对措施，要点是避开密集而强烈的干扰、在接收机中用多种方法滤除干扰、应用具有高编码增益的前向差错控制技术纠正已出现的误码。通过避、滤、纠使地震波形数据的高质量无线传输在攀枝花特有的恶劣环境中得以实现。     

利用数字图像处理技术提高地震剖面图像信噪比

提出了利用数字图像处理技术提高地震剖面信噪比的新方法，首先根据数字图像处理要求的格式，对地震剖面数据进行转换，得到地震剖面图像，分析了地震数据特点和初步地震图像的实验结果后，设计了新的预处理方法——“二维沿层滤波”，在此基础上，利用可以计算帧间运动速度及其变化都较大的改进的光流分析技术，计算出多幅地震剖面对应点的偏移量，然后应用图像积累技术对这多幅地震剖面进行积累，实现对三维地震数据体提高信噪比的处理，该方法充分利用了三维地震信息，不但可以提高整个数据体的信噪比，而且可以减少信号能量的损失，并保持原来的信号能量关系，使地震剖面的质量得到明显提高，为地震解释奠定良好的基础。     

EFFICIENT MULTICHANNEL FILTERING OF SEISMIC DATA1

Multichannel filters are used to eliminate coherent noise from surface seismic data, for wavefield separation from VSP stacks, and for signal enhancement. Their success generally depends on the choice of the filter parameters and the domain of application. Multichannel filters can be applied to shots (monitors), common-receiver traces, CDP traces and stacked sections. Cascaded applications in these domains are currently performed in the seismic industry for better noise suppression and for signal enhancement. One-step shot-domain filtering is adequate for some applications. However, in practice, cascaded applications in shot-and common-receiver domains usually give better results when the S/N ratio is low. Multichannel filtering after stacking (especially after repeated applications in shot and/or receiver domains) may create undesirable results such as artificial continuations, or smearing and smoothing of small features such as small throw faults and fine stratigraphic details. Consequently, multichannel filtering after stacking must be undertaken with the utmost care and occasionally only as a last resort. Multichannel filters with fan-shaped responses (linear moveout filters) should be applied after NMO correction. These are the filters commonly used in the seismic industry where they have such names as velocity filters, moveout filters, f-k filters and coherency filters. Filtering before NMO correction may result in break-up and flattening especially of those shallow reflection events with relatively higher curvatures and diffractions. NMO correction is needed prior to wavefield separation from VSP stacks for the same practical reasons outlined above whenever source-receiver offsets are involved. Creation of artificial lineup and smearing at the outputs of multichannel filters is presently the common practical concern. Optimum multichannel filters with well-defined pass, reject and transition bands overcome the latter problems when applied before stacking and after NMO correction. The trace dimension of these filters must be kept small to avoid such lineups and the smoothing of small structures. Good results can be obtained with only five traces, but seven traces seems to be a better compromise both in surface and well seismic applications. The so-called f-k filtering and τ-p domain filtering are no exceptions to the above practical considerations. Residual static computations after multichannel filtering also need special consideration. Since multichannel filtering improves spatial continuity, residual static algorithms using local correlation, i.e. nonsurface-consistent algorithms, may be impractical especially after multichannel filtering.     

多尺度τ-p谱及其应用

把小波变换与τ-ｐ变换有机地结合起来,本文提出了多尺度τ-ｐ谱的概念,给出了基于多尺度τ-ｐ谱作滤波处理和波场分离的方法．与通常的τ-ｐ变换相比,该方法将x－t域的地震记录变换到（τ,p,a）或（τ,p,f）空间（即多尺度τ-ｐ谱）．多尺度τ-ｐ谱比通常τ-ｐ谱增加了一维,因此用于波场分离或去噪,前者优于后者．若恰当地选择小波函数,该方法抗噪能力强,计算精度高．文中给出了模型及实际地震资料处理实例;证明了此方法的有效性．