共查询到16条相似文献，搜索用时 375 毫秒
1.
2.
针对东营凹陷滩坝砂岩薄砂体的预测识别问题,研究了复小波匹配追踪方法.从地震信号morlet小波分解及重构分析入手,讨论了重构地震信号时关于频率、振幅、相位及时移参数的选取方法及其具体的选取变量.并就关键的振幅参数,研究了改善的计算方法.常规的匹配追踪算法扫描地震信号的所有时间点和频率.在本文中,为了改善时频分辨率,采用局部扫描主频和子波的时间延迟.在具体实现过程中,采用计算地震信号的平均瞬时频率和地震信号的瞬时包络处的时间,做为采样频率和时间采样点,得到与地震信号最佳相关的子波.对研究的方法从理论模型和实际资料进行了论证分析,证明理论上正确合理,实际应用效果显著. 相似文献
3.
本文根据三维液体-固体超声频脉冲振动的模型试验和野外高频地震勘探的结果,对直角断层（θ=90°）、锐角断层（θ<90°）和钝角断层（θ>90°）进行了综合分析。θ角改变时,波的追踪范围和类型均不相同。三种断层中振幅随距离的变化亦不同。当θ=90°时,根据反射波或繞射波振幅随距离变化曲线上的极大值点,可以确定断层的位置;当θ<90°或是θ>90°时,根据振幅曲线上的特征值同样可以确定断层的位置和类型。θ角不同,波的强度变化也不同。不论θ=90°,>90°还是<90°,由一种类型的波向另一种类型的波过渡时,频谱极大值的频率和记录的主周期均有跳跃变化。文中对三种断层做了综合比较,确定了某些基本准则,利用它们可以确定不同类型的断层,这些模型试验结果与野外高频反射波的资料对比,说明它们的特征基本上是一致的。 相似文献
4.
采用短时单频脉冲震源的浅地层剖面,记录的波形数据空间假频较严重。因其信号具有频率高、频带窄的特征,通常利用Hiibert变换提取瞬时振幅属性（信号包络）供解释使用。但瞬时振幅均为正值,在进行构造解释时不方便使用。本文提出在对浅层剖面资料提取瞬时振幅的基础上,计算瞬时振幅的微分并配合滤波的方法,实现高频窄带浅地层剖面资料的一种频移处理。该方法把高频窄带的多周期信号变为低频带宽的单周期信号,有效扩展了倍频程并消除假频。应用在南海浅地层剖面资料处理中,资料处理后更利于构造解释。 相似文献
5.
小波变换与地震信号特征分析 总被引：6，自引：0，他引：6
地震波的瞬时信号,如瞬时振幅、瞬时频率及瞬时相位等,是研究地球介质的重要参数。根据小波定义,对Morlet 小波进行了修正,并对修正后的小波形态进行了深入讨论。理论分析表明,小波变换效果受到整形参数、小波长度、中心频率、频带宽度及小波个数等参数的制约,特别是整形参数与小波中心频率及频带之间关系对小波变换起到决定性作用。在地震波信号的实际处理中,可选取恰当的整形参数,同时采用合适的小波中心频率以避免小波变换对信号产生的遗漏和冗余。文中给出了实际地震记录处理的示例。 相似文献
6.
7.
复地震道分析又称三瞬分析,该分析方法可将反映地震信号局部变化情况的地震波的瞬时振幅、瞬时相位和瞬时频率等信息分离开.本文应用Hilbert变换求解虚地震记录,用复地震道分析方法求取"三瞬"信息,并用该方法计算了理论合成地震记录的瞬时振幅、瞬时相位和瞬时频率,获得了较好的效果.同时,本文也利用该方法对某区块实际地震资料进行了处理,结果表明,复地震道分析方法获得的"三瞬"信息可反映地震信号的局部变化,有助于进行地震薄互层分析,并能提高数据的解释精度. 相似文献
8.
提出一种自适应协方差的时频域极化滤波方法。该方法在广义S变换时频方法的基础上,构造时频域自适应协方差矩阵,通过特征分析计算时频域瞬时极化参数,设计极化滤波器,实现多分量地震极化分析和滤波。其优势在于协方差矩阵的分析时窗的长度由多分量地震数据的瞬时频率确定,可以自适应于有效信号的周期,在每个时频点计算极化参数不需要进行插值处理;结合时间频率信息,解决在时间域或频率域波形或频率重叠的信号具有明显的直观性。模型数据及实际三分量台站地震数据处理结果表明,该极化滤波方法在台站地震资料分析和处理方面具有很好的直观性和较高的分辨率。 相似文献
9.
本文推导并评价了一个新的计算视复电阻率的近似公式,其视振幅表达式为|ρs（ω）|≈ρs（ω）|ρs（ω）=ρs（ω）|,视相位表达式为φs（ω）≈sum from i=1 to n（Bi（ω）φi（ω））,这里Bi（ω）是按各介质复电阻率振幅计算的稀释系数。此近似公式比迄今为止已发表过的同类近似公式都精确,可在频率域激电法数值模拟计算视复电阻率时应用。 相似文献
10.
通过在频率域双程波动方程模拟算法中加入一个复数频率（实部表示频率,虚部表示衰减因子）压制地震波初至走时之后的能量,从而把初至走时及其振幅的计算问题转换为单一频率波场中最大能量走时和振幅的拾取问题,然后利用单一频率域波场的相位项和振幅项分别计算初至走时及其振幅.本文还提出利用参数分析方法求取最优的复数频率,并给出数值计算例子,将本方法的计算结果与有限差分程函方程初至走时和最大能量走时振幅进行比较,结果表明,该方法具有适应于任意复杂介质和多炮多接收点走时和振幅的计算. 相似文献
11.
12.
Enhancement of Signal-to-noise Ratio in Natural-source Transient Magnetotelluric Data with Wavelet Transform 总被引：1，自引：0，他引：1
—For audio-frequency magnetotelluric surveys where the signals are lightning-stroke transients, the conventional Fourier transform method often fails to produce a high quality impedance tensor. An alternative approach is to use the wavelet transform method which is capable of localizing target information simultaneously in both the temporal and frequency domains. Unlike Fourier analysis that yields an average amplitude and phase, the wavelet transform produces an instantaneous estimate of the amplitude and phase of a signal. In this paper a complex well-localized wavelet, the Morlet wavelet, has been used to transform and analyze audio-frequency magnetotelluric data. With the Morlet wavelet, the magnetotelluric impedance tensor can be computed directly in the wavelet transform domain. The lightning-stroke transients are easily identified on the dilation-translation plane. Choosing those wavelet transform values where the signals are located, a higher signal-to-noise ratio estimation of the impedance tensor can be obtained. ? In a test using real data, the wavelet transform showed a significant improvement in the signal-to-noise ratio over the conventional Fourier transform. 相似文献
13.
In the paper, we propose a surface wave suppression method in time-frequency domain based on the wavelet transform, considering the characteristic difference of polarization attributes, amplitude energy and apparent velocity between the effective signals and strong surface waves. First, we use the proposed method to obtain time–frequency spectra of seismic signals by using the wavelet transform and calculate the instantaneous polarizability at each point based on instantaneous polarization analysis. Then, we separate the surface wave area from the signal area based on the surface-wave apparent velocity and the average energy of the signal. Finally, we combine the polarizability, energy, and frequency characteristic to identify and suppress the signal noise. Model and field data are used to test the proposed filtering method. 相似文献
14.
A method to identify the P-arrival of microseismic signals is proposed in this work, based on the algorithm of intrinsic timescale decomposition (ITD). Using the results of ITD decomposition of observed data, information of instantaneous amplitude and frequency can be determined. The improved ratio function of short-time average over long-time average and the information of instantaneous frequency are applied to the time-frequency-energy denoised signal for picking the P-arrival of the microseismic signal. We compared the proposed method with the wavelet transform method based on the denoised signal resulting from the best basis wavelet packet transform and the single-scale reconstruction of the wavelet transform. The comparison results showed that the new method is more effective and reliable for identifying P-arrivals of microseismic signals. 相似文献
15.
Maksim Bano 《Geophysical Prospecting》2004,52(1):11-26
The attenuation of ground‐penetrating radar (GPR) energy in the subsurface decreases and shifts the amplitude spectrum of the radar pulse to lower frequencies (absorption) with increasing traveltime and causes also a distortion of wavelet phase (dispersion). The attenuation is often expressed by the quality factor Q. For GPR studies, Q can be estimated from the ratio of the real part to the imaginary part of the dielectric permittivity. We consider a complex power function of frequency for the dielectric permittivity, and show that this dielectric response corresponds to a frequency‐independent‐Q or simply a constant‐Q model. The phase velocity (dispersion relationship) and the absorption coefficient of electromagnetic waves also obey a frequency power law. This approach is easy to use in the frequency domain and the wave propagation can be described by two parameters only, for example Q and the phase velocity at an arbitrary reference frequency. This simplicity makes it practical for any inversion technique. Furthermore, by using the Hilbert transform relating the velocity and the absorption coefficient (which obeys a frequency power law), we find the same dispersion relationship for the phase velocity. Both approaches are valid for a constant value of Q over a restricted frequency‐bandwidth, and are applicable in a material that is assumed to have no instantaneous dielectric response. Many GPR profiles acquired in a dry aeolian environment have shown a strong reflectivity inside dunes. Changes in water content are believed to be the origin of this reflectivity. We model the radar reflections from the bottom of a dry aeolian dune using the 1D wavelet modelling method. We discuss the choice of the reference wavelet in this modelling approach. A trial‐and‐error match of modelled and observed data was performed to estimate the optimum set of parameters characterizing the materials composing the site. Additionally, by combining the complex refractive index method (CRIM) and/or Topp equations for the bulk permittivity (dielectric constant) of moist sandy soils with a frequency power law for the dielectric response, we introduce them into the expression for the reflection coefficient. Using this method, we can estimate the water content and explain its effect on the reflection coefficient and on wavelet modelling. 相似文献
16.
Gabor变换和S变换是常用的时频分析工具。根据测不准原理,它们的时频分解结果无法在时间域和频率域同时具有很高的分辨率。为了提高非平稳信号时频分解结果的分辨率,本文提出瞬时频率分布函数（IFDF）并利用它表达非平稳信号。当非平稳信号时频成分的分布满足测不准原理对信号可分辨的要求时,瞬时频率分布函数的支集和短时Fourier变换的小波脊支集是同一个集合。利用IFDF的该特征,本文提出一种迭代算法（Sparse-STFT）实现了信号的稀疏时频分解。该算法在每次迭代过程中利用残留信号的短时Fourier变换结果的脊支集更新信号的时频成分,每次迭代得到的时频成分的叠加结果即为最终的稀疏时频分解结果。文中的数值实验证明了Sparse-STFT可以有效地提高非平稳信号时频分解结果的分辨率。最后,本文将该方法应用于地震数据面波的压制中,取得了理想的处理结果。 相似文献