基于小波与分形理论的地震异常检测

A method of detecting seismic singularities using combined wavelet with fractal

为了提高地震异常检测精度,探讨了小波与分形结合的地震异常检测方法.首先采取功率谱密度对地震波的分形性质进行分析,得出其具有且仅在几个高频段具有自仿射分形性质,这为分形的合理应用提供了依据并揭示了现有单一综合分形维方法的不足;继而提出了频率、时间有序的无次采样小波包变换(FOTO- NWPT) ,该算法为地震波分形分析创造了优良平台.基于前两者,提出了小波与分形优势结合的地震异常检测方法:由FOTO- NWPT将地震波分解在若干尺度上,依据尺度关联维分析构建地震剖面分形参数空间,参数奇异标志了地震异常.工程实验证明,该方法比现有方法的科学性和实用性更强,为实现度量参数化精细地震勘探提供了一条新的思路.

A new method of utilizing combined wavelet with fractal to detect seismic singularities is proposed aiming at improving the detecting precision. Firstly the fractal property of seismic wave is comprehensively investigated based on its power spectrum density analysis, and the conclusion is made that seismic wave is of self-affine fractal property only in several higher frequency bands. This not only provides the theoretic foundation for reasonably applying fractal into seismic wave analysis, but also reveals the shortage of employing single integrated fractal dimension to detect seismic singularities. Secondly an algorithm of frequency and time-ordered non-decimated wavelet packet transform is put forward to produce excellent platform for fractal analysis of seismic wave. On the basis of the above two aspects, a wavelet-fractal based method for detecting seismic singularities is developed, which consists of three successive steps: seismic wave is decomposed into multi-scale coefficient sequences, and then fractal-parameter space of seismic profile is constructed depending on the correlation dimension analysis of effective scale coefficient sequences; in the end, singular parameters are identified and they indicate the seismic singularities. An engineering example shows that the proposed method outperforms the existing wavelet and fractal concerned methods in rationality and practicability, so it provides a new approach for parameterized accurate seismic geophysical prospecting.