## 2 The Case Study  
### The Seismic Sequence  
On 20 May 2012, the Emilia-Romagna region in northern Italy was struck by an M\({}_{w}\) 5.8 earthquake (Figure 1), resulting in devastating damage and loss of life. In the following days, thousands of aftershocks were enucleated, six with a magnitude greater than 5, with the most significant aftershock, measuring M\({}_{w}\) 5.6, occurring on 29 May [27] (Figure 1). The seismic activity activated two segments of the Ferrara-Romagna thrust system, namely the Ferrara thrusts and the Mirandola thrusts (Figure 1). The rupture initially propagated eastward and downdip on the Ferrara thrust system. Then, it moved westward on the adjacent Mirandola thrust, leading to the M\({}_{\rm w}\) 5.6 aftershock [26; 27]. The moment tensor solutions for the stronger events displayed a reverse focal mechanism [28]. More than 70% of the earthquakes occurred within three months after the first shock, while the events with a magnitude greater than five happened in the first 15 days. A whole picture of the regional ground displacement pattern is provided first by two Radarsat-2 (RSAT-2) SAR images, acquired on 30 April and 17 June 2012, respectively, and spanning both the 20 and 29 May main events [29; 30]. The unwrapped interferogram (Figure 1) shows that the ground moved toward the satellite Line of Sight (LoS) (positive values in (Figure 1) over an area encompassing the seismic activity in the hanging wall of the main shocks. A significant component of this motion involved uplift across the Ferrara and Mirandola thrust faults, peaking at approximately 16 cm close to the Finale Emilia town [26; 29]. The study area corresponds to the buried frontal portion of the compressive ramp and flat structures of the Apennines [32]. The earthquake sequence occurred over an alluvial plain representing the surface expression of the foredeep basin of the Apennine chain, where a combination of fast subsidence and substantial sediment input generated very thick Plio-Pleistocene successions made of alternating layers of coarse-grained and fine-grained deposits [33]. Figure 1: Sketch of the area affected by the 2012 Emilia earthquake sequence. The thrusts of Ferrara and Mirandola depict the tectonic framework (from [PERSON] et al. [26]). The color map shows the unwrapped co-seismic displacements along the Line of Sight of the descending track of the RSAT-2 satellite mission encompassing the 20 and 29 May events (30 April–17 June 2012; side-looking angle 30\({}^{\circ}\); negative and positive values identify movements away and towards the satellite sensor, respectively; modified from [PERSON] et al. [29] and [PERSON] et al. [30]). The location of liquefaction phenomena is provided by Emergeo Working Group [31]. The dashed purple line identifies the partial boundary of the COSMO-SkyMed (CSK) SAR frame, located over the Sant’Agostino, San Carlo, and Mirabello villages. Seismicity is available from the INGV database ([[https://terremoti.ingv.it/](https://terremoti.ingv.it/)]([https://terremoti.ingv.it/](https://terremoti.ingv.it/)), accessed on 8 February 2024). In this context, many phenomena occurred after the mainshock. Wells near the epicentral area experienced a sudden increase in water level [34], testifying to a sustained regional perturbation of the deep and shallow aquifers because of tectonic dislocation [30; 35; 36]. Periodic sampling of the liquid and gaseous phases in surficial aquifers also indicated a rise in deep-seated fluids along faults and fractures, which altered the geochemical composition of fluids belonging to shallower aquifers [37]. Additionally, over 700 liquefaction phenomena were observed, particularly in the area encompassed by the San Carlo and Sant'Agostino villages [31; 38] (red dots in Figures 1 and 2a,b). Sand boils, water leaks from cracks at the ground surface, gravitational lateral spreading, and a widespread pattern of ground subsidence were reported, often distributed along elongated strips, corresponding to fluvial buried sandy bodies of the Holocene age [39].