Local Maximum Second Order Multi-Synchrosqueezing Transform for High Resolution Surface-Wave Group Velocity Dispersion Energy Imaging

Surface-wave group velocity dispersive energy imaging is a crucial technique for determining near-surface shear wave velocities. The conventional method based on time-frequency analysis (TFA) has a low resolution and low estimation accuracy at the low-frequency end. To address this issue, we made improvements in two aspects. On the one hand, we proposed a novel TFA method that incorporated the concept of local maxima into the second-order multisynchrosqueezing transform to achieve high-resolution and reliable time-frequency (TF) representations. On the other hand, the classical unnormalized cross-correlation sum method in seismic velocity analysis was introduced to improve the accuracy of group velocity estimation. The synthetic and field data test results demonstrated that the group velocity dispersion energy imaging resolution of the proposed method was significantly higher than that of the generalized S-transform (GST) method. Furthermore, our method required only three traces with an interval of 20 m to achieve good results.