## 3 Results and Discussion
### The 2018 \"Plowing\" Event
This effect is also clearly enhanced in the northwestern part of the area due to the presence of topography. Figure 4: **(a)** Sketch of the tire marks left by the truck on 27/01/2018 (as inferred based on photographic evidence in [22; 23]), with indication of the position of the truck during the incident (black star; as inferred based on the video in [24]); and **(b–e)** InSAR coherence \(\gamma\) for the COSMO-SkyMed StripMap pairs: **(b)** 18/01/2018–26/01/2018 (pre-event); **(c)** 26/01/2018–30/01/2018 (cross-event); **(d)** 10/01/2018–30/01/2018 (cross-event); and **(e)** 13/12/2017–30/01/2018 (cross-event). Figure 3: Analysis of the 27/01/2018 event: **(a)** Google Earth overview of the Pan-American Highway (VHR image © 2018 DigitalGlobe), with the locations of the event and Observation Tower marked by the dashed rectangle and oval, respectively; and **(b–e)** InSAR coherence \(\gamma\) for a series of COSMO-SkyMed StripMap pairs: **(b)** 18/01/2018–26/01/2018 (pre-event); **(c)** 26/01/2018–30/01/2018 (cross-event); **(d)** 10/01/2018–30/01/2018 (cross-event); and **(e)** 13/12/2017–30/01/2018 (cross-event). * Pan-American Highway: here decorrelation occurs as an effect of cars and trucks driving along the road and thus generating temporal decorrelation in all InSAR pair combinations. The effects of vehicular decorrelation are more evident with increasing temporal baselines. For instance, pair 13/12/2017-30/01/2018 in Figure 3e with a \(B_{t}\) of 48 days shows a much more marked decorrelation feature along the highway than pair 18/01/2018-26/01/2018 in Figure 3b with a \(B_{t}\) of only 8 days. * Observation Tower: at this location, coherence loss extends some meters off the Pan-American Highway due to the transit of tourists visiting the tower. Decorrelation is observed both to the southwest of the highway at the tower location (e.g., Figure 3c), and to the opposite side, where its small parking lot occupies an area of about 10 by 20 m adjacent to the highway (e.g., Figure 3d,e; see also Figure 2b). * January 2018 incident: decorrelation in the three cross-event InSAR pairs is observed in the area identified as that affected by the 2018 event (Figure 3c-e). A detailed analysis of coherence for this area is provided in Figure 4b-e, where the same InSAR pairs are shown by zooming in at the local scale. In the pre-event 18/01/2018-26/01/2018 pair (Figure 4b), there are no obvious coherence loss marks other than those along the highway due to vehicle transit and a few spots of possible human/vehicle transit along the verge of the highway. On the other hand, some very noticeable marks appear in the three cross-event pairs in Figure 4c-e. The decorrelation marks seem to follow the exact path that was followed by the truck during the incident, with the main linear feature originating from the highway and moving off it towards the guardhouse. The feature is best depicted in the InSAR pair 13/12/2017-30/01/2018 (Figure 4e) which is the cross-event pair characterised by the smallest \(B_{p}\) but longest \(B_{t}\) among all the cross-event pairs. Comparison of the pre- and post-event Sentinel-2 scenes for this area (Figure 5) confirms the occurrence of a slight surface reflectance change, even at the 10-m image resolution. The increase in reflectance is due to plowing of the surface and uncovering of the light grey-yellow clay underneath the darker pebble constituting the surface of the Pampa. It is to be noted, however, that the spatial resolution of Sentinel-2 data does not allow precise spatial delineation of the site disturbance at the scale of this event. In this case, a post-event optical scene with higher spatial resolution would have been necessary to identify accurately the surface reflectance change marks. No post-event VHR imagery is, however, currently available via Google Earth, where the most recent scene for this location dates back to 20/10/2014.