## 3 Materials and Methods
### SAR Data and Interferometric Processing  
Space-born synthetic aperture radar (SAR) imagery is routinely utilized for measuring co-seismic surface displacements based on the DInSAR technique. DInSAR allows mapping the co-seismic motion by using two satellite images taken before and after an earthquake [56; 57; 58]. The systematic availability of SAR data from the Copernicus Sentinel-1 mission, with a revisiting time of 6 days over Europe (12 days globally), as well as the wide swath coverage of 250 km, enables the near-real-time response to seismic events [59; 60; 61; 62; 63].  
The contribution of platform-based solutions in the early response phase of an earthquake has been well demonstrated [64; 65]. The Geohazards Exploitation Platform (GEP; [[https://geohazards-tep.eu](https://geohazards-tep.eu)]([https://geohazards-tep.eu](https://geohazards-tep.eu)), accessed on 23 January 2022) focuses on mapping hazard-prone land surfaces and monitoring terrain motion, providing access to several Earth Observation (EO) missions and a broad range of relevant online services and development on cloud processing resources [66].  
The present work utilized Sentinel-1 data acquired during the period from 23 September to 1 October 2021, with different viewing geometries to optimize the displacement map generation. For the interferometric processing, the GEP DIAPASON service was exploited, considering precise orbit state vectors and SRTM Digital Elevation Model 3-arcsecond (\(\approx\)90 m) data to remove the topographic phase. Interferometric measurements correspond to movements detected along the Line-of-Sight (LoS) of the satellite, i.e., the oblique direction between the satellite and the Earth's surface. Positive LoS values indicate uplift or motion towards the satellite, whereas negative ones correspond to subsidence or motion away from the sensor. The DInSAR processing scheme implemented herein is described in detail in [67; 68]. Four differential interferograms were generated for the descending 036 (D036) and 109 (D109) orbital tracks, as well as for the ascending 102 (A102) and 029 (A029) ones, with temporal separation of 6 to 12 days and spatial resolution of approx. 45 m. Figure 4 and Figure S2 in the Supplementary Materials show the obtained displacement fields, while Table 1 details the interferometric pairs considered for the various geometries. Based on their temporal coverage, it is important to note that each co-seismic displacement map is affected by a different contribution of post-seismic motion. The interferograms for tracks A102 and D036 represent those with the smallest and largest post-seismic contribution, respectively (Figure 4).  
Furthermore, due to the opposite geometries, independent LoS measurements were decomposed into vertical (Up) and E-W-motion components, to facilitate the optimal interpretation of motion patterns. The horizontal and vertical components were calculated using both Sentinel-1 geometries in a comprehensive decomposition scheme [69], considering the variability of the incidence angles within the scenes. In order to simplify the geometrical assumptions, only measurements of similar incidence angles were considered in the decomposition (i.e., orbital tracks A102--D036 and A029--D109) (see Table 1).