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正演模拟是瑞雷面波研究的一个主要方面,目前对于瑞雷面波的正演研究大多是基于均匀层状弹性介质条件下的瑞雷面波频散曲线方程,这只适用于层状模型,无法模拟全波场,而且不考虑实际介质的黏弹效应.本文采用交错网格高阶有限差分法对黏弹性介质中的瑞雷面波进行了高精度全波场模拟,并对频散特征进行了提取与分析.其中采用属于非线性最优化的Levenberg-Marquarat方法直接计算松弛时间来拟合常Q模型,并将应力镜像法与紧致差分格式相结合来准确实施自由表面条件,在其余边界处以非分裂的多轴卷积完全匹配层为吸收边界.然后利用相移法从地震记录中提取频散剖面并对几种典型模型的面波频散特征进行了对比分析.结果表明黏弹性对面波的频散特性有显著影响,面波勘探中有必要考虑黏弹性因素.
Forward modeling is one of the main aspects of Rayleigh wave research. At present, most studies on the Rayleigh wave are based on the Rayleigh wave dispersion curve equation under the condition of uniform layered elastic medium, which is only applicable to the layered Model can not simulate the whole wave field and does not consider the viscoelastic effect of the actual medium.In this paper, the staggered-grid high-order finite difference method is used to simulate the Rayleigh wave in viscoelastic medium with high accuracy and full-wave field, The Levenberg-Marquarat method, which belongs to non-linear optimization, is used to directly calculate the relaxation time to fit the constant Q model and to combine the stress image method with the compact difference scheme to accurately implement free surface conditions. And the non-splitting multi-axis convolution perfect matching layer is taken as the absorption boundary at the other boundary.Secondly, the phase-shift method is used to extract the dispersion profile from the seismic records and the surface wave dispersion characteristics of several typical models are compared and analyzed.The results show that Viscoelastic opposite wave dispersion characteristics have a significant impact, surface wave exploration is necessary to consider the viscoelastic factors.