横向非均匀介质多道瑞雷波频散曲线正演

作为近地表横波速度结构成像的主要手段之一,面波多道分析法的正问题研究对现场观测系统设计及后续反演计算具有重要意义.目前面波频散曲线的正演主要分为两类:一是对水平层状介质中面波的本征值问题进行求解,该类方法计算效率高但较难考虑地下介质在横向上的不均匀性;二是基于波动方程的全波场模拟,该类方法在理论上可考虑任意复杂的地质模...

Forward modeling of multichannel Rayleigh wave dispersion curve in laterally inhomogeneous media

Multichannel analysis of surface wave(MASW)method has been one of the effective tools for retrieving near-surface shear-wave velocity.As with other geophysical methods,its forward problem is of great importance to the design of the field survey and the solution of the inversion.Currently,the forward algorithms of surface wave dispersion curve are generally classified into two categories:solution of surface wave eigenproblems in a horizontally layered model,which is time-efficient but difficult to consider lateral variations;and wave equation-based full wavefield simulation,which can theoretically deal with any complicated geological model but requires high computational costs.In this paper,we present a forward algorithm of multichannel Rayleigh wave dispersion curves in laterally inhomogeneous media based on amplitude-normalized beamforming.By analyzing the formula of beamforming,the relationship between the local phase velocity and the phase velocity in the power spectrum estimated by the amplitude-normalized beamforming is derived,and then the theoretical dispersion curve of multichannel Rayleigh wave data is calculated by utilizing the Golden Section search method.Numerical results show that the proposed algorithm can quickly and efficiently calculate the theoretical dispersion curve of multichannel Rayleigh waves in laterally inhomogeneous media.The difference between dispersion curves calculated by the proposed algorithm and produced by the 2D elastic wave finite-difference time-domain algorithm is small,which indicates the reliability of the proposed algorithm.The proposed forward algorithm can provide a theoretical foundation for the inversion of dispersion curves in laterally inhomogeneous media and an efficient tool for the optimization design of the MASW acquisition system.