Speaker
Description
Abstract:
The Einstein Telescope gravitational wave observatory aims to achieve a sensitivity down to 3 Hz, where Newtonian noise becomes a dominant disturbance. Seismic waves propagating in the surrounding soil generate density fluctuations that induce gravitational forces on the suspended mirrors. Since these forces cannot be shielded, they must be estimated from the seismic wave field and subtracted from the interferometer data.
In realistic site configurations the seismic wave field is obtained using numerical wave propagation models that account for soil layering and underground structures. The remaining step is the evaluation of the gravitational acceleration from the computed displacement field.
A finite element formulation for Newtonian noise analysis has been recently developed and implemented in the ANNA Newtonian Noise Analysis toolbox [1]. The Newtonian noise is computed from three-dimensional seismic wave fields using a finite element formulation. The gravitational acceleration is obtained by numerical integration of density perturbations using Gaussian quadrature, leading to finite element operators that directly map the displacement field to the Newtonian noise contributions.
In this work, the methodology is extended to account for layered geological formations. A multi-criteria meshing strategy is introduced, in which the domain size and mesh refinement required by the Newtonian noise integrals are consistently addressed over a frequency range. Seismic wave fields are constructed in the layered medium, and the contribution of motion in each layer to the total Newtonian noise is quantified. The resulting framework enables the prediction of Newtonian noise in heterogeneous subsurface configurations and provides a basis for application to realistic site data.
[1] P. Reumers, X. Kuci, S. François, and G. Degrande. ANNA: a toolbox for Newtonian Noise Analysis. https://arxiv.org/abs/2603.15157