Imaging high-temperature geothermal reservoirs with ambient seismic noise tomography, a case study of the Hengill geothermal field, SW Iceland

•High-resolution 3D seismic noise tomography of the Hengill geothermal field.•Potential of seismic noise tomography in geothermal exploration.•Constraining the current thermal state of high-enthalpy geothermal reservoirs.•Identifying an attractive location for the Iceland Deep Drilling Project.•Delineating the bottom of the steam cap through the iso-velocity of 2 km/s. The Hengill volcanic system is located in the Reykjanes Peninsula (Iceland) and hosts two large geothermal power plants: Nesjavellir and Hellisheiði. This area is the next target for the Iceland Deep Drilling Project (IDDP) to search for super-critical fluids. Here, we investigate the potential for ambient seismic noise tomography to be used as a geothermal exploration tool. The results are compared with different geophysical observables, of which resistivity modeling shows an excellent correlation with our results. We also observe a prominent seismic velocity reduction to the south of Hverahlíð, where the most powerful boreholes in the region are located.