Distributed Acoustic Sensing (DAS) for Geothermal Applications: a Case Study Across Dublin City

Seismic monitoring plays an integral role in geothermal renewable energy projects for imaging, site-specific noise characterisation and hazard risk assessment purposes. The number of European geothermal energy projects is expected to rise over the next decade as efforts to mitigate for reliance on fossil fuel-derived energy sources continue. Related to this is the pressing need to prospect for and expand the use of geothermal energy in urban settings.

Distributed Acoustic Sensing (DAS) is increasingly applied in lieu of geophone-based deployments. Instead of measuring seismic waves at a limited number of discrete points, DAS transforms fibre-optic cables into large and dense arrays of virtual sensors by measuring small changes in strain rate, with gauge length resolutions as small as 1-20 metres. DAS interferometry is able to capitalise on extant urban fibre-optic infrastructure, as well as exploit the diverse and passive seismic noise sources available in towns and cities.

Here we present in-progress DAS data analysis from an approximately 70-80km long cable crossing Dublin city (south to north) for three weeks of cumulative recording between September-October 2025. This cable tracks a large portion of the M50 ring road, the main arterial traffic route between north and south Dublin. We identify and characterise the main noise sources as a function of space and time, comparing DAS signals with temporally overlapping broadband seismometer data. We discuss possible approaches to suppress incoherent noise along the cable for future shallow and deep geothermal monitoring, as well as imaging applications using coherent noise.

This research feeds into the European Union-funded Clean Energy Transition partnership project, GEOTWINS, which seeks to extend the state-of-the-art in modular geothermal digital twins, for improved deep geothermal imaging methodologies, drilling risk mitigation and to progress societal acceptance.