High-resolution multimode surface-wave dispersion spectrum imaging with a multichannel signal comparison method

High-resolution surface-wave dispersion spectrum imaging is crucial for estimating the shallow subsurface S-wave velocity based on the dispersion properties. In global seismic exploration, linear signal comparison (LSC) method is widely used to compute the dispersion spectrum, which uses only two seismic records. However, LSC relies on a cross-correlation strategy that leads to poor resolution in the low-frequency regions. Nonlinear signal comparison (NLSC) approach overcomes the resolution problem and can achieve high-resolution imaging by using the exponential function. However, we find that LSC and NLSC both suffer a severe problem: the higher modes imaging is inaccurate since the dispersion properties are not fully considered by utilizing only two recorded data. Based on the multichannel acquisition system in active source surface wave exploration, multichannel signal comparison (MSC) method takes all the signals into account, which can obtain an accurate multimode dispersion spectrum. However, MSC method needs to compare the signals of every two records that cause the problem of redundant calculation and low efficiency. Therefore, we improve the computational efficiency of MSC method by tracing the surface wave in the shot gathers. By comparing with the theoretical dispersion curves, we verify the effectiveness of the modified MSC method. Through comparing with the phase shift method, LSC, and NLSC, we demonstrate that MSC is a high-resolution and high-precision surface-wave multimode dispersion spectrum imaging approach. The application of field data reveals the great potential of MSC method in extracting multimode surface wave dispersion information in shallow seismic exploration. © 2021, Science Press. All right reserved.