低速带对瑞雷波振幅变化特征的影响研究  

Study on the Influence of Low Velocity Layer on Rayleigh Waves

作　　者：颜廷容 孙成禹 王志农 张利振 杜燚镜 Yan Tingrong;Sun Chengyu;Wang Zhinong;Zhang Lizhen;Du Yijing(School of Geosciences,China University of Petroleum,Qingdao Shandong 266580,China)

机构地区：[1]中国石油大学地球科学与技术学院,山东青岛266580

出　　处：《工程地球物理学报》2023年第1期132-141,共10页Chinese Journal of Engineering Geophysics

基　　金：国家自然科学基金面上项目(编号:42174140);国家自然科学基金(编号:41874153)。

摘　　要：在地震勘探中,地球表面往往存在一个低速覆盖层,为了研究在理想条件下传播和有低速覆盖层时传播的振幅变化特性,从瑞雷波的基本性质出发展开公式推导,得出瑞雷波的速度方程和位移方程,然后对模型进行地球物理参数赋值,最后进行数值试算,画出瑞雷波的频散曲线和振幅曲线。根据频散曲线和振幅曲线研究不同模型因素影响下的瑞雷波的速度特征和振幅特征变化,进而由此综合分析推断出瑞雷波在非理想自由界面条件下的瑞雷波性质和瑞雷波振幅随低速覆盖层不同参数的变化曲线。通过数值计算可以得出瑞雷波在有低速带的时候会发生频散现象,振幅会随深度的增加发生衰减,而且频率越高,衰减的速度越快,当低速层越厚,衰减速度会更快,而当横波速度变大,会减缓衰减速度。In the case of actual exploration,the earth’s suface is often not free and is usually covered with a low-velocity layer,so it is necessary to study the characteristics of Rayleigh wave with low-velocity layer.This paper studies the characteristics of Rayleigh wave,propagating in ideal condition and low-velocity layer condition.Using the basic theory of Rayleigh wave to derive wave equation and free interface boundary condition to work out the displacement equation and velocity equation,then set geophysical parameters on the model.Finally,through calculating,the dispersion curve and displacement curve are obtained.According to the dispersion curve and amplitude curve,the velocity and amplitude characteristics of Rayleigh waves are studied under the influence of different model factors.Then the amplitude and velocity properties of Rayleigh waves under the non-ideal free interface conditions and the variation curve of wave amplitude with different parameters of low-velocity overburden are deduced.Through numerical calculation,it can be concluded that Rayleigh wave dispersion phenomenon occurs in low-velocity zones,the amplitude attenuates with the increase of depth,and in higher frequency,the attenuation speed is much faster.When the low-velocity layer is thicker,the attenuation speed is faster and with the increase of shear wave velocity,the degree of attenuation slows down.

关 键 词：低速带 瑞雷方程 频散曲线 位移方程 

分 类 号：P631.4[天文地球—地质矿产勘探]