Seismic wavefield characteristics in translational and rotational components for isolated velocity-anomaly bodies in two-dimensional shallow media

With the increasing utilization of underground space, detecting shallow isolated velocity-anomaly bodies such as karst and boulder has become a critical challenge in engineering seismic exploration. This study employs the finite-difference algorithm to investigate two-dimensional seismic wavefields in translational (X and Z) and rotational (Y) components for homogeneous half-space and layered medium models that incorporate low-velocity and high-velocity spheres. The dispersion characteristics analyses of Rayleigh wave for these models are conducted to compare the wavefield differences caused by shallow velocity-anomaly bodies using the methods including Multichannel Analysis of Surface Wave, Horizontal-to-Vertical Spectral Ratio (HVSR), and Rotational to Vertical-and-Horizontal Spectral Ratio (RVHSR). Results demonstrate that the velocity-anomaly bodies cause noticeable influences on kinematics and dynamics dispersion characteristics of Rayleigh waves, which can be visually depicted on the rotational Y component. It can be more effective to accurately delineate the property and spatial distribution of underground velocity-anomaly bodies by combining the seismic response of translational and rotational components.