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. •Exploration of shallow velocity anomalies by phase velocity and ellipticity characteristics of Rayleigh waves.•Rotational motion can be applied to shallow engineering seismic exploration.•Propose spectral ratio calculated by joint translational and rotational components to explore shallow velocity anomalies.