Monitoring seismic hazard with satellite geodesy in Italy: first steps for the integration of GNSS and European Ground Motion Service data

The potential role of satellite geodesy techniques for seismic hazard assessment, with particular focus on GNSS and InSAR, has been widely investigated in the last decades. These technologies can detect differences in ground velocity of less than one millimeter per year, and could therefore be suitable to highlight the accumulation of tectonic strain. While conventional strain field estimation is performed from a two-dimensional planimetric point of view, a novel approach was introduced by incorporating the independent a-priori tectonic knowledge of the study area to pre-select the directions along which strain accumulation signs should be searched [1, 2]. This method was applied to the earthquakes of Amatrice (2016) and Emilia (2012), analyzing the ground velocity estimated from GNSS station data along two transects of interest. Despite the promising results obtained, the spatial density of GNSS stations was too low to provide a detailed description of the velocity profile along the transects. In this sense, the combination of GNSS and InSAR techniques could greatly improve these analyses. The recent European Ground Motion Service (EGMS) [3] constitutes an ideal dataset to pursue this objective. In the present work, we evaluated the suitability of EGMS data for seismic hazard assessment. To achieve this, we defined transects covering known high seismic hazard regions of Italy, following the scheme outlined in [2], but greatly improving both the spatial resolution along the transects and their inter-distance, leveraging the high spatial density of InSAR measurement points. We evaluated the velocity profile along the transects using the data provided by the EGMS service, and compared the results obtained with velocities measured from GNSS station data, both projecting GNSS data along the satellite line of sight and retrieving displacements eastward and upward considering SAR acquisitions from ascending and descending orbits. Through this comparison we assessed whether the accuracy, the revisiting time and the covered temporal window of EGMS data are sufficient to ensure a correct velocity estimation, and took a first step in the direction of a future integration. Preliminary results obtained in the Irpinia region (Italy) suggested a good performance of EGMS data for the detailed description of the velocity profile and an excellent agreement with GNSS station data.