复杂地区地震资料低信噪比的原因及对策(二)——表层散射波的基本性质及形态特征
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摘要
为了对散射波有进一步的认识以及为压制技术提供基础依据,采用从散射源与对应散射波都比较简单、直观的记录入手,由简单到复杂、由个别到一般的基本方法,对其基本性质及形态特征进行研究。对三维空间而言,当散射源位于测线或离测线很近时,单个散射波形态是线性或近于线性的,且可分为正向散射、反向散射和双向散射;当散射源距离测线较远时,散射波形态是双曲型的;散射波的顶点位于散射源在测线的投影点;两翼趋势线与面波平行或基本平行。散射波主要分布于面波所夹的三角区内;散射波频率多为几个赫兹到约30Hz;速度与面波速度相当。实际记录的复杂干扰背景主要是众多单个散射波的叠加结果。在复杂地区,散射干扰是导致记录低信噪比的根本原因。上述结论是对干扰波(散射波)认识的重大进展,对散射波的压制有指导意义。
This paper aims to further understand the nature of scattered waves and provide basic data for the development of scattered wave suppression techniques.Therefore,from simple to complex and from specific to general,we studied the basic properties and shapes of scattered waves,beginning with the simple and visualized seismic records of both scattering sources and corresponding scattered waves.In 3-D space,a single scattered wave is in linear or near linear shapes and can be classified into forward scattered wave,reverse scattered wave,and bidirectional scattered wave when the scattering source is located on or close to seismic lines.In contrast,scattered waves show hyperbolic curve shape when the scattering source is far away from the seismic lines.The crest of a scattered wave is located at the subpoint of the scattering source on seismic lines.The trend lines on both sides are parallel or sub-parallel to surface waves.Scattered waves mainly occur in the triangle area between surface waves,their frequencies are in the range from several to 30 Hz or so,and their velocities are similar to those of surface waves.The complex interference setting of real seismic records is resulted from the superimposition of numerous single scattered waves.Scattered wave interference is the basic cause of a low signal-to-noise ratio in complex areas.These understandings can contribute to the suppression of scattered waves.
This paper aims to further understand the nature of scattered waves and provide basic data for the development of scattered wave suppression techniques.Therefore,from simple to complex and from specific to general,we studied the basic properties and shapes of scattered waves,beginning with the simple and visualized seismic records of both scattering sources and corresponding scattered waves.In 3-D space,a single scattered wave is in linear or near linear shapes and can be classified into forward scattered wave,reverse scattered wave,and bidirectional scattered wave when the scattering source is located on or close to seismic lines.In contrast,scattered waves show hyperbolic curve shape when the scattering source is far away from the seismic lines.The crest of a scattered wave is located at the subpoint of the scattering source on seismic lines.The trend lines on both sides are parallel or sub-parallel to surface waves.Scattered waves mainly occur in the triangle area between surface waves,their frequencies are in the range from several to 30 Hz or so,and their velocities are similar to those of surface waves.The complex interference setting of real seismic records is resulted from the superimposition of numerous single scattered waves.Scattered wave interference is the basic cause of a low signal-to-noise ratio in complex areas.These understandings can contribute to the suppression of scattered waves.
引文
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