起伏地表粘弹复杂介质三维多分量瑞雷波传播特性研究

This research will first study dispersive characteristics, dissipative characteristics, and excition mechanisms of Rayleigh waves by staggered-grid high-order finite-difference modeling and numerical simulations based on linear viscoelastic media. Second, dynamics of 3D This research will first study dispersive characteristics, dissipative characteristics, and excition mechanisms of Rayleigh waves by staggered-grid high-order finite-difference modeling and numerical simulations based on linear viscoelastic media. Second, dynamics of 3D Rayleigh wave propagation, such as mechanisms of waveform distortions, dispersion splitting, mode jump and mode osculation, will fully be revealed. Reflection, diffraction, and amplitude decay of 3D Rayleigh wave seismic wavefields will be analyzed as well. Third, to improve imaging quality and signal-to-noise ratio of true 3D Rayleigh waves in complex terrain, arbitrary acquisition geometry and multi-component receivers will be used. Fourth, high-precision and high-resolution S-wave velocity models can be obtained by 3D multiscale full waveform inversion, which can exploit full recorded amplitude and phase in wavefields. Finally, by comparisions between 3D multiscale full waveform inversion and dispersion inversion, as well as real-world examples, this research will widen conventional theories of Rayleigh waves, obtain new findings, and will promote the progress of high-precision Rayleigh wave exploration.

本项目以线性粘弹介质模型为基础，通过开展起伏地表粘弹复杂介质三维瑞雷波高精度有限差分模拟，进行三维瑞雷波频散特性、衰减特性和激发特性研究，阐释三维瑞雷波传播动力学特征，深入揭示三维瑞雷波波形畸变机理、频散分裂机理、模式跳跃、模式干涉和模式接吻机理，解析三维瑞雷波反射、散射和共鸣震荡现象；通过三维多分量阵列分布式野外采集和频散曲线提取，进行真三维瑞雷波多分量采集，提高其对三维起伏地表复杂地质结构的照明度、透视力和信噪比；通过多尺度全波形反演，充分利用瑞雷波记录的全波场振幅和相位信息，进行高精度和高分辨率横波速度建模，增强瑞雷波在起伏地表和横向非均匀介质中勘探适应性，提高其对复杂构造和较小地质体的三维精细刻画能力；通过多尺度全波形反演与三维频散曲线反演对比及实例分析，构建起伏地表粘弹复杂介质三维多分量瑞雷波新的传播理论及应用方法，获得新的发现，拓宽现有瑞雷波理论范畴，推动瑞雷波高精度勘探发展。

由于传统瑞雷波勘探主要基于水平地表弹性各向同性层状介质模型假设，利用单分量瑞雷波进行勘探，然而实际山区地质结构更接近于起伏地表粘弹复杂介质模型。因此导致现有瑞雷波推断起伏地表粘弹复杂介质结构时仍然精度不高，有时甚至会导致错误的地质解释，其应用领域也受到了很大限制。.鉴于此，本项目以线性粘弹介质模型为基础，开展了起伏地表粘弹复杂介质三维瑞雷波高精度有限差分正演模拟研究，进行了三维瑞雷波频散特性、衰减特性和激发特性研究，阐释了三维瑞雷波传播动力学特征，深入揭示了三维瑞雷波波形畸变机理、频散分裂机理、模式跳跃、模式干涉和模式接吻机理，解析了三维瑞雷波反射、散射和共鸣震荡现象。通过三维多分量阵列分布式野外采集和高分辨率频散曲线提取，进行了粘弹介质真三维阵列分布式瑞雷波多分量采集，克服了二维线型排列单分量采集接收的缺陷；基于重力场重心点学术思想进行了真三维瑞雷波频散曲线提取；通过主动源与被动源联合利用增强了瑞雷波低频段频散曲线提取可靠性，进而提高了瑞雷波对三维起伏地表复杂地质结构的照明度、透视力和信噪比。开展了真三维多模式瑞雷波频散曲线行列式目标函数进行快速稳定反演，克服了传统目标函数反演计算速度慢和易出现模式误识别等问题；利用联合概率密度统计分析MPPD的学术思想对反演模型的多解性和可靠性进行了分析评价。通过多尺度全波形反演，充分利用了瑞雷波记录的全波场振幅和相位信息，进行了高精度和高分辨率横波速度建模，增强了瑞雷波在起伏地表和横向非均匀介质中勘探适应性，提高了其对复杂构造和较小地质体的三维精细刻画能力；通过瑞雷波多尺度全波形反演与三维频散曲线反演对比及实例分析，构建了起伏地表粘弹复杂介质三维多分量瑞雷波新的传播理论及应用方法，拓宽了现有瑞雷波理论范畴，推动了瑞雷波高精度勘探发展。