Speaker
Description
Accurate prediction of seismic noise and Newtonian noise is essential for characterizing candidate sites for the Einstein Telescope (ET), a third-generation underground gravitational-wave observatory. Near-surface settings with a low-velocity sedimentary layer overlying hard rock can strongly modify the seismic wavefield and, consequently, the associated Newtonian noise. In this study, we perform 2D numerical simulations by solving the viscoelastic seismic wave equation to investigate how sediment geometry and material properties influence seismic wavefields and the resulting Newtonian noise. The test models are designed to represent an unconsolidated, low-velocity sediment layer over hard rock, and the noise sources are randomly distributed and driven by random time series. We first compare models with flat and curved sediment-hard-rock interfaces to analyze the effect of interface geometry. The flat-interface model produces strong resonance due to interference among waves reflected within the sediment layer. We then systematically examine the sensitivity of the simulated wavefield and noise response to variations in shear-wave velocity and attenuation. Lower shear-wave velocity leads to stronger trapping of seismic energy within the shallow sedimentary layer, whereas stronger attenuation causes more energy to be dissipated within the sediment. These results provide a framework for assessing how realistic low-velocity sediment structure affects seismic and Newtonian noise, with potential implications for site characterization and noise prediction in geologically heterogeneous shallow structures.