【摘要】 在地震勘探中,可以利用现有大炮地震记录中的瑞利面波频散信息提取频散曲线,进而反演近地表的速度结构,建立高密度的表层结构剖面。准确地提取瑞利面波频散曲线是提高近地表结构反演精度的前提。但由于地震勘探中大炮地震记录的道间距过大,利用频率—波数变换法提取频散曲线时,空间假频难以避免,这必然影响频散曲线提取和反演的效果。本文通过分析理论模型空间假频对频散曲线提取的影响,发现大道间距引起的空间假频会导致提取的频散曲线缺失高频信息,并通过频散曲线敏感度的理论分析,发现频散曲线高频部分对浅层横波速度更敏感。利用等厚分层阻尼最小二乘联合反演,分别对理论模型和实际数据进行了不同道间距的横波速度反演,反演结果表明空间假频引起的频散曲线高频段缺失会增大反演的整体相对误差,降低浅层反演精度和反演的稳定性,进而影响反演效果。更多还原

【Abstract】 Near surface velocity structure and high-density structure profiles can be built by inverting the dispersion curve extracted from the Rayleigh-wave in seismic shot gathers.The accurate extraction of Rayleigh-wave dispersion curve can ensure the accuracy near surface structure inversion.However,spatial aliasing will affect dispersion curve extraction and the inversion of dispersion curve because of large receiver intervals in seismic shot gathers.Using a theoretical model,we find that the spatial aliasing causes high frequency information lack on the dispersion curve by large receiver intervals.We also find that high frequency dispersion curve is more sensitive to shear wave velocity of shallow layers.The joint inversion with the isopath layered and damped least squares is applied on both synthetic model and real data with different receiver intervals.Both of the tests demonstrate that the high frequency lack on dispersion curve increases the relative error of inversion,and harms the inversion stability due to the spatial aliasing.更多还原