## 5 Discussion
### Conceptual Scheme of the Observed Phenomenon  
Considering our results, we proposed a simple exploratory scheme, as shown in Figure 8, to support our conclusions about the observed displacements and further discuss the time delay in the consolidation process.  
Based on the typical geotechnical cross-section shown in Figure 2, we represented the stratigraphic column of the first 30 m of the study area in Figure 8a. The seismic shaking during the earthquake sequence led to excess pore pressure (depicted by the blue plus symbols in Figure 8b), which caused liquefaction of the saturated sandy layers. Our working assumption is that the arrangement of the main architectural elements of the alluvial succession below the groundwater table depth determines whether liquefaction may occur in the field.  
The liquefaction of the shallower sandy layers, especially those located within or below the braided paleo-drainages and abandoned meanders, had widespread effects on the ground, such as sand boils and water leaks from cracks. This was also accompanied by nearly instantaneous local subsidence (Figure 8b) ([PERSON], 2016; [PERSON], 2016). Excess pore pressures caused an upward flow of a sufficient volume and speed to lift soil particles and carry them to the ground surface. As a result, the pore water typically found or created cracks or holes through which it could flow to the surface. Indeed, the distribution of liquefaction effects seemed aligned with channel-levee complexes and is associated with prominent geomorphological features or lateral spreading effects in the study area ([PERSON], 2016; [PERSON], 2016).  
The absence of sand ejecta in other areas does not mean that sandy layers at depth did not liquefy. According to [PERSON] et al. [67], if the top of the liquefied layer is too deep, sand boils will not form, even if liquefaction below the crust does occur, because the upper, non-liquefiable layer is too thick. Therefore, we expect that liquefaction occurred also in the deep sand layer, as shown in Figure 8b [8]. For these layers, which are confined between thick clay deposits [41; 42], the pore water pressure dissipation is not as fast as the shallower layers, but is governed by the in-series seepage flow across both sandy and clay-like layers. The speed of in-series groundwater flow and pore pressure dissipation is governed mainly by the layer with the lowest permeability, which, in this case, is represented by the clay-like layer, characterized by low permeabilities of the order of k = 2-3 \(\times\) 10\({}^{-9}\) cm/s [40]. Such behavior could explain the approximately 4- to 5-month timespan required to achieve asymptotic subsidence.  
Consequently, a slow consolidation process developed, with a progressive displacement accumulation over time (Figure 8c). Other strong aftershocks during the seismic sequence could have also enhanced excess pore pressures [40], even producing new liquefaction effects at the ground (e.g., sand ejecta) and re-liquefaction at some sites [38], thus extending the pore pressure dissipation time.  
The observed ground displacements from the InSAR analysis confirm the proposed scheme, since the observed ground subsidence manifested independently at the location of liquefaction-related manifestations at the ground (Figure 4). Moreover, the amplitude of the observed displacements was compatible with the computed consolidation values, thus providing further confirmation about the origin of the post-liquefaction consolidation of the observed ground movements.