Seismic noise characterization at a potential gravitational wave detector site in Australia

TL;DR

This study characterizes low-frequency seismic noise at a potential gravitational wave detector site in Australia, analyzing environmental influences like wind and human activity to inform detector design.

Contribution

It provides a detailed seismic noise profile of the Gingin site, distinguishing between wind-induced and anthropogenic noise sources using beamforming techniques.

Findings

Wind noise affects seismic coherence at high wind speeds.

Seismic noise between 1-10 Hz is lower than at Virgo due to less human activity.

Microseism levels are higher than at Virgo, but overall noise is lower in the 1-10 Hz range.

Abstract

A critical consideration in the design of next generation gravitational wave detectors is the understanding of the seismic environment that can introduce coherent and incoherent noise of seismic origin at different frequencies. We present detailed low-frequency ambient seismic noise characterization (0.1--10~Hz) at the Gingin site in Western Australia. Unlike the microseism band (0.06--1~Hz) for which the power shows strong correlations with nearby buoy measurements in the Indian Ocean, the seismic spectrum above 1~Hz is a complex superposition of wind induced seismic noise and anthropogenic seismic noise which can be characterized using beamforming to distinguish between the effects of coherent and incoherent wind induced seismic noise combined with temporal variations in the spatio-spectral properties of seismic noise. This also helps characterizing the anthropogenic seismic noise. We show that wind induced seismic noise can either increase or decrease the coherency of background seismic noise for wind speeds above 6~m/s due to the interaction of wind with various surface objects. In comparison to the seismic noise at the Virgo site, the secondary microseism (0.2~Hz) noise level is higher in Gingin, but the seismic noise level between 1 and 10~Hz is lower due to the sparse population and absence of nearby road traffic.