Characterization of the seismic environment at the Sanford Underground Laboratory, South Dakota

TL;DR

This study characterizes the seismic noise environment at Sanford Underground Laboratory, analyzing seismic data and external sources to evaluate its suitability for advanced gravitational-wave detectors.

Contribution

It provides a detailed seismic noise profile at various depths, highlighting the 4100-ft level as an exceptionally low-noise environment for sensitive experiments.

Findings

4100-ft level has the lowest seismic noise among studied depths

Seismic noise correlates with oceanic microseisms and surface wind speeds

Long-term spectral variations reveal seismic source characteristics

Abstract

An array of seismometers is being developed at the Sanford Underground Laboratory, the former Homestake mine, in South Dakota to study the properties of underground seismic fields and Newtonian noise, and to investigate the possible advantages of constructing a third-generation gravitational-wave detector underground. Seismic data were analyzed to characterize seismic noise and disturbances. External databases were used to identify sources of seismic waves: ocean-wave data to identify sources of oceanic microseisms, and surface wind-speed data to investigate correlations with seismic motion as a function of depth. In addition, sources of events contributing to the spectrum at higher frequencies are characterized by studying the variation of event rates over the course of a day. Long-term observations of spectral variations provide further insight into the nature of seismic sources. Seismic spectra at three different depths are compared, establishing the 4100-ft level as a world-class low seismic-noise environment.