The impact of seasonality over the sensitivity of Einstein Telescope and the SNR of CBC signals at the Sardinia candidate site

TL;DR

This study assesses how seasonal seismic noise variations at the Sardinia site affect the Einstein Telescope's low-frequency sensitivity and the SNR of compact binary signals, finding minimal impact.

Contribution

It provides a detailed analysis of seasonal seismic noise effects on ET sensitivity and SNR, supporting site suitability for low-frequency gravitational wave detection.

Findings

Seismic noise varies seasonally but has limited impact on ET sensitivity.

SNR of binary signals is affected by only a few percent due to seasonal noise.

Sardinia site remains suitable for ET low-frequency performance despite seasonal variations.

Abstract

This work investigates the impact of seasonal variations in seismic noise on the low-frequency performance of the Einstein Telescope (ET) at the Sardinia candidate site, focusing on implications for compact binary coalescence observations. Using seismic data collected between 2022 and 2025 in deep boreholes, we characterize monthly noise variations and identify representative best and worst case scenarios, corresponding to July and December. The measured seismic spectra are used to estimate the Newtonian noise contribution in the 2-10 Hz band and to derive modified ET sensitivity curves. These are implemented in a simulation framework to evaluate their effect on the signal-to-noise ratio (SNR) of binary neutron star and intermediate mass black hole signals, assuming the triangular ET configuration. We find that the low seismic noise of the Sardinia site results in only minor seasonal variations in detector sensitivity. The corresponding impact on SNR is limited to a few percent, even without including Newtonian noise mitigation. These results indicate that seasonal environmental fluctuation have a minor effect on the early inspired detectability of compact binaries, confirming the suitability of the Sardinia site for achieving ET low-frequency sensitivity goals.