A travel-time tomography method for improving horizontal resolution of high-frequency surface-wave exploration

作者：Yin XiaoFei; Xu HongRui^*; Xia JiangHai; Sun ShiDa; Wang Peng

来源：Acta Geophysica Sinica, 2018, 61(6): 2380-2395.

DOI：10.6038/cjg2018L0373

• Horizontal resolution
• Pure-path phase-velocity dispersion curves
• Travel-time tomography method of surface waves
• A pseudo-2D S-wave velocity section

In high-frequency surface-wave methods, horizontal resolution refers to the ability to distinguish anomalous objects that are laterally displaced from each other. The horizontal length of a recognizable geological anomalous body is measured by the scale of shear (S)-wave velocity anomalies. The multichannel analysis of surface wave (MASW) method is an efficient tool to determine near-surface S-wave velocity. However the inverted 1D S-wave velocity model is an averaged geophysical model under the receiver spread length, thus the MASW method has low horizontal resolution. In addition, the common middle point (CMP) roll-along acquisition method can increase the amount of fieldwork by the roll-along acquisition geometry. To solve these problems, on the basis of the MASW method, we propose a complete technique flow to improve horizontal resolution of surface-wave exploration by the travel-time tomography method. Firstly, we use the wave field separation technique to obtain accurate fundamental or higher mode of surface waves. And surface-wave phase-velocity dispersion curves between any two traces are calculated by the combined method of cross-correlation and phase-shift scanning from a multichannel record. Then with the application of travel-time tomography method, we obtain high resolution pure-path phase-velocity dispersion curves at diverse sizes of grids. Finally, the pseudo-2D S-wave velocity structure is reconstructed by inverting pure-path phase-velocity dispersion curves. The proposed method can effectively enhance the ability of random noise immunity, and can extract accurate surface-wave phase-velocity dispersion curves from a record with a short receiver spacing theoretically. Moreover, the pseudo-2D S-wave velocity structure can be obtained by the proposed method with at least only one seismic record, which reduces the amount of fieldwork dramatically. A synthetic test and a real-data example have demonstrated that the proposed method has a great potential in improving the horizontal resolution of surface wave exploration using multichannel analysis.

• 出版日期2018-6
• 单位中国地质大学（北京）; 中国地震局地震预测研究所; 浙江大学; 华中科技大学