Defining the shallow geothermal potential by using the seismic microzonation data: a case study from the Southern Marche Region to encourage a sustainable post 2016-earthquake reconstruction

The use of renewables is of paramount importance for sustainable development and economic growth. In this context, shallow ground-sourced heat exchangers (GSHEs) coupled with geothermal heat pumps represent a valuable opportunity for heating and cooling systems both in urban and rural areas. The regions of the Central Italy affected by the 2016 seismic sequence (Mmax 6.5), while involved in the post-earthquake reconstruction, could greatly benefit from the installation of GSHEs, which are environmental-friendly and with two peculiarities among the renewables: (i) continuous source of thermal energy and (ii) landscape protection (GSHEs are not visible). Here the focus is set on the evaluation of the shallow geothermal potential for the southern sectors of the Marche Region, with the aim of producing maps favouring the knowledge of the heat that could be extracted through GSHEs from different rocks of the subsoil. As a first pilot area we selected the upper-middle portion of the Potenza river fluvial plain to quantitatively estimate the values of key parameters such as the thermal conductivity, the volumetric heat capacity of the subsoil and the specific heat extraction. We followed the methods described in Taussi et al. (2021), thus averaging the geothermal parameters values over the first 100 meters, i.e. the most common depth of GSHEs. In order to assign the representative values for the shallow heat exchange parameters, the local stratigraphy was reconstructed on the basis of the surveys and data (mainly geognostic drillings) made available by the Civil Protection, thanks to the completion of the third level of the seismic microzonation studies. This freely accessible database might represent a valuable tool and source of information for such shallow geothermal studies in many different areas, and thus we recommend its use, given the relatively easy availability. In addition, the possibility (and the reliability) to use geophysical surveys (such as MASW or HVSR analyses) data, typically available in such databases, will be tested in order to independently estimate and compare the values of the most relevant shallow geothermal parameters. Preliminary results indicate that higher values for thermal conductivity (> 1.9 W∙m-1∙K-1) and volumetric heat capacity (> 2.35 MJ∙m-3∙K-1) characterize the uppermost sector of the fluvial plain of the study area, especially those areas around San Severino Marche and the ridges corresponding to Treia and Pollenza, where the, respectively, carbonate and siliciclastic bedrocks occur at relatively shallow depths. The development of GSHEs for heating and cooling systems should be really regarded as an opportunity for the reconstruction of these areas hit by the 2016 earthquake.