摘要
近地表广泛分布的小尺度非均匀介质严重影响地震数据和成像质量.本文引入参数化的随机介质来描述近地表非均匀介质;借助功率谱、相关长度、均方根扰动等随机统计特征量研究近地表非均匀介质层对地震波传播、散射及成像的影响;通过成像过程的点弥散函数表述成像分辨率.利用数值方法建立模型的随机统计特征量与成像分辨率特征量之间的关系,以定量或半定量的方式研究二者之间的相关性.数值计算结果表明,近地表非均匀介质层的厚度、速度扰动的幅度以及非均匀体的尺度等都对地震数据质量和成像品质有明显的影响.以全数值方法建立起关于近地表非均匀介质复杂性和地下成像质量之间的关系,有望成为研究近地表非均匀介质对地震数据采集和成像分辨率影响的有效工具.
In land acquisition,particularly in western China,small-scale heterogeneities are often prevail on the near surface.Strong scatterings generated by this layer can seriously affect the quality of data acquisition and depth imaging.Although it has received wide attention in the industry and research community,there is still lack of an effective way to investigate the relations between the shallow heterogeneities and the quality of the depth imagery.In this paper,we introduce the parameterized random velocity model to simulate the velocity heterogeneities in the shallow subsurface,which thus permits to use the statistical parameters such as the randomspectra,correlation length,and root mean square velocity perturbation to describe the highly complicated small-scale heterogeneities.In the meantime,we introduce the point spreading function to investigate the image quality.The point spreading function and its amplitude and phase spectra in the wavenumber domain provide useful information to characterize the quality of the image.This simplifies descriptions for both the complex shallow velocity models and the distortions of depth image,making it possible to create a concise relationship between the two.We further use numerical calculations to correlate statistical parameters of random models to the characteristics of point spreading functions,for quantitatively investigating the relationship between shallow heterogeneities and the depth image.The proposed method is validated by numerical examples.The results show that the thickness of the random layer,the root mean square velocity perturbation and the correlation length all apparently affect the quality of the depth image.
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第5期1762-1775,共14页
Chinese Journal of Geophysics
基金
加州大学圣克鲁斯WTOPI(Wavelet Transform On Propagation and Imaging) Consortium资助
