Gravity fluctuations produced by ambient seismic fields are predicted to
limit the sensitivity of the next-generation, gravitational-wave
detector Einstein Telescope at frequencies below 20 Hz. The detector
will be hosted in an underground infrastructure to reduce seismic
disturbances and associated gravity fluctuations. Additional mitigation
might be required by monitoring the seismic field and using the data to
estimate the associated gravity fluctuations and to subtract the
estimate from the detector data, a technique called coherent noise
cancellation. In this paper, we present a calculation of correlations
between surface displacement of a seismic field and the associated
gravitational fluctuations using the spectral-element SPECFEM3D
Cartesian software. The model takes into account the local topography at
a candidate site of the Einstein Telescope at Sardinia. This paper is a
first demonstration of SPECFEM3D's capabilities to provide estimates of
gravitoelastic correlations, which are required for an optimized
deployment of seismometers for gravity-noise cancellation.