最佳数字滤波器及其应用

最佳数字滤波器是分离有给定周期的波或消除时间序列中短周期波动的有效数学工具。它可分成三种类型:低通滤波器、带通滤波器和高通滤波器。 本文提出一个计算正弦积分的新公式。在不同的地质领域内使用了最佳数字滤波器     

消除地震前兆观测中干扰的一种DAI数字滤波器

本文介绍了一种DAI数字带通滤波器,这种滤波器能根据数据处理需要选择滤波参数。参数确定后,可计算出滤波器的频率响应,根据频率响应的好坏确定是否重新选择滤波参数,直到满意为止。滤波的误差可以在滤波器设计中给定,适当增加褶积的项数即滤波器的长度,可以使滤波的误差很小。本文用这种方法处理了地下水位观测资料,消去固体潮汐的影响。其效果比用潮汐理论值校正的方法消去潮汐影响更好。本文还用频移的方法将这种带通滤波器变成低通滤波器,用来消去视电阻率的年变化。直接用带通滤波提取水氡观测值中周期在半个月到两年的变化成分。这种滤波方法在以上应用中均得到了较好的效果。     

数字滤波器在高台地震台地震记录日常分析中的应用

简要介绍了滤波器的一般原理与Butterworth低通滤波器、高通滤波器和带通滤波器在高台地震台日常工作中的应用。     

航空重力数据无限脉冲响应低通数字滤波器设计与试验研究

采用巴特沃思(Butterworth)和切比雪夫(Chebyshev)逼近,设计无限脉冲响应(Infinite Impulse Response,IIR)低通数字滤波器,对GT-1A航空重力勘查系统的测量数据进行了滤波试验研究,结果表明,通过选择合适的通带和阻带衰减等滤波参数,IIR低通数字滤波器在航空重力数据的低通滤...     

应用FIR滤波器消除天津数字地震记录中的干扰

数字地震记录中包含大量的干扰信号,影响数据质量,需要加以排除。针对天津数字地震记录中存在的干扰信号,介绍了FIR数字滤波器的原理与方法,并详细阐述了利用汉宁窗函数的带阻滤波器、高通滤波器滤除天津数字地震记录中的干扰,从而达到突出地震信号特征、消除干扰的目的。实践表明:这种方法设计简单、方便、实用性强、具有良好的效果。     

短周期与宽频带数字地震计记录波形相关分析

为了研究短周期与宽频带数字地震观测系统的一致性,分别对山东地震台网青岛、济南、荣成、五莲、烟台的5个同一摆墩上安装的两套观测系统记录的同一地震事件波形资料进行了相关性分析。先将宽频带记录通过等波纹带通滤波器进行频带为1~20 Hz的滤波处理,再将短周期记录进行过采样处理,实现与宽频带记录的采样率一致。分析表明,宽频带和短周期地震计记录近震、地方震和非天然近距离地震波形在形态上一致,地震波形的振幅和相位存在较好相似性,震中距越近地震波形振幅和相位的相似度越高,宽频带和短周期地震计得到速度震级间差别不大,一致性较好。     

唐山地震前后脉动变化的研究

本文简要地叙述了选频脉动测量仪的基本原理和特性。利用低通和带通数字滤波器,分别对脉动、风速和气压等资料进行了处理。结果表明,脉动与局部气象条件的相关性不大;唐山7.8级地震前不久,离震中不远的昌黎台（△=80公里）记录到的脉动幅值急剧减小;在几次强余震（M≥6.0）前,脉动幅值经历较长时间（数月）的偏低过程,而临震前变化不明显。结合唐山地震前,邻近震中地区地温（80厘米深）的时、空分布特征,讨论了它们与唐山地震孕震过程的可能联系。     

通过系数映射设计二维环状对称滤波器

在地球物理学中二维滤波器用于处理地震、位场及遥感数据资料,也用于其它应用科学如图象处理.经过映射技术用最优化一维算法来设计这些滤波器:把二维期望响应映射成时间域或频率域的一维响应,得到近似后再映射回来.这里提出了一种设计二维环状对称滤波器的系数映射算法.二维频率域系数按照它们距原点的距离分选后映射到一维的频率轴上.在系数映射到一维频率轴上之前,这种分选使环状对称滤波器的特定通带、阻带或过渡带的系数归在一起.结果在一维频率域内有着与相应二维频率域内同样多的指定频带,这就导致在一维域内最佳近似.因此,也能在二维域内有最佳近似.这种映射在Nyquist域间进行. Chebychev或“最小最大”算法已用于一维近似计算.由于二维与一维之间是—种完全映射,经映射所设计的二维滤波器表现出与一维滤波器相似的等脉动特性.这种新的映射算法适合于设计多频带的低通、高通、带通以及带阻滤波器.近似频响的环状对称性随着滤波系数的增加有所改进.对N_1×N_2系数的二维滤波器,N_1、N_2一定要为奇数;但不一定相等.应用低通、高通滤波器,对区域重力场测量数据进行处理,结果证实在无谱重叠时这些滤波器能有效地分离不同波长的异常.     

根据数字滤波器的频率响应优选数字处理方法

本文根据数字滤波器压制干扰的原理,指出利用数字滤波器的频率响应、优选数字处理方法和确定最佳滤波参数的具体原则。对于那些未给出频率响应函数或周期选择性函数的数字处理方法,可以直接根据计算方法的权系数算出它们的频率响应。计算递归滤波器的频率响应式子,也可以用来计算其它非递归滤波器的频率响应。本文利用重力固体潮汐分析中计算中心点的零点飘移值若干方法的系数和它们的周期选择性函数,分别计算了它们的频率响应,从两者的数值上比较,结果是一致的。本文还计算了目前大家常用的一些数字处理方法,如五日均值、一阶差分、二阶差分、多点数字平滑等方法的频率响应值。并分析了它们的处理效果和方法的局限性。还根据最佳数字滤波器和DAI数字滤波器的频率响应曲线,说明选择数字滤波器和确定最佳滤波参数的具体方法。     

地震遥测数据传输中数字滤波器的实现

从理论上讨论了几种数字滤波器的工作原理及实现方法。着重分析了经典滤波器、统计滤波器和相关检测的工作原理,并给出了各滤波器系统的分析方法和传递函数,简化了数字滤波器的实现过程。为寻找到适合于地震数据传输的滤波方法做出了有益的探索。     

An efficient and self‐adaptive approach for Q value optimization

The time‐invariant gain‐limit‐constrained inverse Q‐filter can control the numerical instability of the inverse Q‐filter, but it often suppresses the high frequencies at later times and reduces the seismic resolution. To improve the seismic resolution and obtain high‐quality seismic data, we propose a self‐adaptive approach to optimize the Q value for the inverse Q‐filter amplitude compensation. The optimized Q value is self‐adaptive to the cutoff frequency of the effective frequency band for the seismic data, the gain limit of the inverse Q‐filter amplitude compensation, the inverse Q‐filter amplitude compensation function, and the medium quality factor. In the processing of the inverse Q‐filter amplitude compensation, the optimized Q value, corresponding gain limit, and amplitude compensation function are used simultaneously; then, the energy in the effective frequency band for the seismic data can be recovered, and the seismic resolution can be enhanced at all times. Furthermore, the small gain limit or time‐variant bandpass filter after the inverse Q‐filter amplitude compensation is considered to control the signal‐to‐noise ratio, and the time‐variant bandpass filter is based on the cutoff frequency of the effective frequency band for the seismic data. Synthetic and real data examples demonstrate that the self‐adaptive approach for Q value optimization is efficient, and the inverse Q‐filter amplitude compensation with the optimized Q value produces high‐resolution and low‐noise seismic data.     

井间地震资料精细解释方法研究与应用

井间地震资料分辨率很高,但是缺乏成熟的解释方法,本文针对井间地震资料的特点,借鉴地面地震解释技术对井间地震资料开展了精细解释方法研究.首先在深度域资料特点分析的基础上,利用区域速度和层析成像速度将深度域井间地震资料转换到时间域进行研究,并通过粗化降频建立起井间地震资料与地面地震资料之间的相似性联系,得到对井间地震低频反射特征的认识,结合井旁道合成地震记录标定建立起井间地震资料的反射特征,准确的解释了井间地震的反射层位.采用地震瞬时属性分析和时频属性分析得到了对沉积环境的认识,进一步通过波阻抗反演更好的认识井间储层特征.在实际应用中综合多种方法进行解释,并结合测井资料对比落实了井间砂体展布特征,得到对井间储层的精细描述结果,解决了两口井之间储层分布范围、横向连通性及厚度变化等问题,取得了较好的应用效果.     

MATLAB软件在鹤岗地震台地震观测记录中的应用

随着数字化地震计的应用和发展,数字观测资料中不仅记录了宽频带地震信息,也包含了大量的干扰信号。在实际工作中,对地震信息的分析处理影响很大,有时还会造成地震波形记录不完整或地震信号淹没在干扰信号中,很难再进行深入的分析和应用。因此,利用MATLAB软件设计IIR数字滤波器对不同记录中的干扰波进行滤波器设计,达到消除干扰波的目的。实例表明,此方法在台站应用效果良好。     

Implementation aspects of attenuation compensation in reverse‐time migration

Attenuation compensation in reverse‐time migration has been shown to improve the resolution of the seismic image. In this paper, three essential aspects of implementing attenuation compensation in reverse‐time migration are studied: the physical justification of attenuation compensation, the choice of imaging condition, and the choice of a low‐pass filter. The physical illustration of attenuation compensation supports the mathematical implementation by reversing the sign of the absorption operator and leaving the sign of the dispersion operator unchanged in the decoupled viscoacoustic wave equation. Further theoretical analysis shows that attenuation compensation in reverse‐time migration using the two imaging conditions (cross‐correlation and source‐normalized cross‐correlation) is able to effectively mitigate attenuation effects. In numerical experiments using a simple‐layered model, the source‐normalized cross‐correlation imaging condition may be preferable based on the criteria of amplitude corrections. The amplitude and phase recovery to some degree depend on the choice of a low‐pass filter. In an application to a realistic Marmousi model with added Q, high‐resolution seismic images with correct amplitude and kinematic phase are obtained by compensating for both absorption and dispersion effects. Compensating for absorption only can amplify the image amplitude but with a shifted phase.     

Optimization of sub-band coding method for seismic data compression

Seismic data volumes, which require huge transmission capacities and massive storage media, continue to increase rapidly due to acquisition of 3D and 4D multiple streamer surveys, multicomponent data sets, reprocessing of prestack seismic data, calculation of post‐stack seismic data attributes, etc. We consider lossy compression as an important tool for efficient handling of large seismic data sets. We present a 2D lossy seismic data compression algorithm, based on sub‐band coding, and we focus on adaptation and optimization of the method for common‐offset gathers. The sub‐band coding algorithm consists of five stages: first, a preprocessing phase using an automatic gain control to decrease the non‐stationary behaviour of seismic data; second, a decorrelation stage using a uniform analysis filter bank to concentrate the energy of seismic data into a minimum number of sub‐bands; third, an iterative classification algorithm, based on an estimation of variances of blocks of sub‐band samples, to classify the sub‐band samples into a fixed number of classes with approximately the same statistics; fourth, a quantization step using a uniform scalar quantizer, which gives an approximation of the sub‐band samples to allow for high compression ratios; and fifth, an entropy coding stage using a fixed number of arithmetic encoders matched to the corresponding statistics of the classified and quantized sub‐band samples to achieve compression. Decompression basically performs the opposite operations in reverse order. We compare the proposed algorithm with three other seismic data compression algorithms. The high performance of our optimized sub‐band coding method is supported by objective and subjective results.     

昆仑山口西8. 1级地震的地震活动特征

在回顾昆仑山口西8. 1级地震前的长期、中期的不同阶段不同程度的预测意见基础上,对该次地震前的地震活动进行了分析。结果表明, 该次巨大地震前存在地震条带、地震空区、地震活动增强区、象限性等空间异常及地震活动参数异常, 这些特征对巨大地震的研究与预测具有重要的参考作用。     

一种自适应增益限的反Q滤波

地层的Q吸收会造成地震波振幅衰减、相位畸变,分辨率和信噪比明显降低.反Q滤波可消除由于地层Q吸收造成的振幅衰减和相位畸变,从而提高地震资料的分辨率;但反Q滤波振幅补偿的数值不稳定性问题会严重降低地震资料的信噪比,并产生很多假象.截止频率法和稳定因子法反Q滤波振幅补偿方法虽可控制数值非稳定性问题,但振幅补偿函数的增益限为一个时不变的常数,且与地震数据动态范围无关,其经常会压制深层地震波的高频成分,反而降低地震资料的分辨率;因此,本文在研究截止频率法和稳定因子法的基础上,结合地震数据的动态范围对地震记录分辨率的影响,提出了一种自适应增益限的反Q滤波振幅补偿方法,其增益限和稳定因子都是时变的,且都自适应于地震数据有效频带的截止频率.合成数据和实际数据试算表明,本文的自适应增益限的反Q滤波方法可恢复地震信号有效频带范围内的能量,且能较好地控制数值非稳定性问题,最终获得高分辨率和高信噪比的地震数据.     

IMPROVEMENT OF MULTICHANNEL SEISMIC DATA THROUGH APPLICATION OF THE MEDIAN CONCEPT1

Different types of median-based methods can be used to improve multichannel seismic data, particularly at the stacking stage in processing. Different applications of the median concept are described and discussed. The most direct application is the Simple Median Stack (SMS), i.e. to use as output the median value of the input amplitudes at each reflection time. By the Alpha-Trimmed Mean (ATM) method it is possible to exclude an optional amount of the input amplitudes that differ most from the median value. A more novel use of the median concept is the Weighted Median Stack (WMS). This method is based on a long-gapped median filter. The implicit weighting, which is purely statistical in nature, is due to the edge effects that occur when the gapped filter is applied. By shifting the traces around before filtering, the maximum weight may be given to, for example, the far-offset traces. The fourth method is the Iterative Median Stack (IMS). This method, which also includes a strong element of weighting, consists of a repeated use of a gapped median filter combined with a gradual shortening of the filter after each pass. Examples show how the seismic data can benefit from the application of these methods.     

OPTIMUM HYPERBOLIC MOVEOUT FILTERS WITH APPLICATIONS TO SEISMIC DATA*

Optimum multichannel filters can be designed to process seismic events falling on hyperbolic moveout curves using the conventional least-squares method. Contrary to the linear moveout filters, autocorrelation and crosscorrelation functions inherent in the normal equations have to be computed numerically. However, computation times of filter coefficients are comparable to linear moveout operators. For a given source-receiver geometry and assuming straight ray-path, relative moveout of a seismic reflection event is dependent on the two way arrival time and rms velocity. Consequently, to avoid overlapping of pass and reject moveout windows, hyperbolic moveout filters have to be designed over time gates rather than for the whole record lengths. Hyperbolic and hyperbolic-linear moveout filters applied to synthetic and field seismic reflection traces show good signal-to-noise (S/N) ratio improvements. Results of some combined synthetic and field data examples are presented.