The GEO-URBAN Project: Exploring the Geothermal Potential of Dublin City using Electromagnetic and Passive Seismic Methods

The GEO-URBAN project aims to understand the potential of the geothermal district heating in Dublin City to respond to increasing demand for sustainable energy sources. To help elucidate the subsurface geology in the geothermal exploration effort, we perform a multi-disciplinary approach using two innovative and complementary geophysical techniques: (i) electromagnetics and (ii) passive seismics. We implement and test the feasibility of these methods to investigate the electrical conductivity and velocity variations beneath the city. The geology of Dublin City is characterised by a Carboniferous sedimentary basin separated from the Lowerpalaeozoic basement by bounding faults. The depth of the basement is unclear, but presumably between 1.5 to 2 km deep. We have deployed a broadband seismic array across the city to collect a dataset of ambient noise over a 4-month period, to be used for the single station H/V analysis and the array cross-correlation interferometry. The H/V analysis results show an overall high resonance frequency peak indicating a shallow soil layer across the study area. The preliminary cross-correlation results are promising and indicate the emergence of surface waves. To test the feasibility of the electromagnetic techniques in the urban areas, we conducted a magnetotelluric experiment in Dublin City. The first data acquisition results show that the time series were heavily contaminated by Dublin City tram/railway systems and other infrastructure. We are currently developing a work strategy to apply passive and controlled-source electromagnetic techniques within the Dublin Basin.