利用改进的F-K变换法提取瑞雷波的频散曲线

Rayleigh wave dispersion curve imaging using improved F-K transform approach

瑞雷波成像能够有效的探测近地表的横波速度结构,准确的提取瑞雷波的频散曲线是该技术的关键.F-K变换法是一种常见的提取频散曲线的方法,然而传统的F-K变换法由于受到震源频带范围和介质滤波作用的影响,计算的频散能量通常集中在较窄的频带范围内,其余频带的能量受到压制,因此提取出的频散曲线频带范围较窄,高阶模式不易识别,为了克服这种缺陷,我们提出一种改进的F-K变换法,提高了该方法提取高阶模式频散曲线的能力.在本文中,我们首先介绍了改进的F-K变换法的原理与计算步骤,然后分别利用传统的和改进的F-K变换法对理论模型正演模拟和实际采集的瑞雷波数据进行处理,将两种方法得到的频散能量图进行对比,结果表明改进的F-K变换法能够呈现出分辨率更高的频散信息,保证了高阶模式频散曲线的有效提取.

Rayleigh wave imaging is an efficient tool to estimate shear wave velocity in near-surface explorations. One key step of this technology is accurately determining the dispersion curves of Rayleigh wave. F-K transform is a commonly used dispersion curve imaging approach,however,the dispersive energy of this approach is severely affected by the amplitude of wave field which distributed in a narrow frequency band, the energy peaks also uneven distributed at different modes. In order to overcome these shortages,we propose an improved F-K transform approach for high resolution multi-mode dispersion curve imaging. In this paper, we first introduce the principle and steps of the improved F-K transform,then comparison has been made between conventional and improved F-K transform using both synthetic and real-world data. Results show that the improved F-K transform successfully enhance the higher order dispersive energies and bring a higher resolution of dispersion imaging.