## 4 Results  
### Quantifying the Deformation of the North Bastion of the City Wall  
What remains of the northern bastion of the city wall (Figure 3(1)) is a sturdy 1.25 m wide piece of wall made up of limestone ashlars and crowned by a solid bastion up to 6 m thick. Nowadays, a segment of the city wall 49 m in length is archaeologically conditioned and preserved. The city wall and bastion are strongly deformed. In the field, tilting of up to 30 degrees from the original 90 degrees at which the wall and bastion were built can be measured. Seen in plan view, the entire construction is also deformed by a series of folds with a vertical axis that give a wavy appearance to what remains of the wall (Figure 6A).  
Once a DEM of the eastern canvas of the wall was obtained and rotated 90\({}^{\circ}\) for convenience (see Figure 5 in the methodological section), a series of derived models could be obtained. As usual, the hillshade model gave us a perception of the visual morphology of the reconstructed element, from which we can interpret and map the best-observed defor  
Figure 6: (**A**) Orthophoto of the northern bastion of the city walls obtained in this work. Note the strong deformation in the form of folds with a vertical axis and the relevant tilting of the most northeastern part of the east side of the city wall. (**B**) Hillshade model of the east side of the city wall and bastion. (**C**) Hyposometric distribution of the horizontal displacement from the vertical in cm on the E side of the city wall; note the different sectors all constrained by the deformation caused by the earthquake. Those sectors correspond with fractures and overall folding. (**D**) Vertically exaggerated topographic profile along the mid part of the remains of the studied wall. The profile shows up to five folds developed in the city wall. (**E**) Slope distribution (dip in degrees) along the studied side of the city wall. Note how the city wall is more tilted towards the NE. (**F**) Aspect model of the east panel of the wall coherent with the deformation depicted in D and F. Note that models B and C were obtained from a DEM with 1 mm of pixel resolution and models E and F with a 10 cm DEM pixel resolution.  
mation features, in this case, the fractures (Figure 6B). On the other hand, a hyposymetric distribution allowed us to characterize the domains/segments of the studied canvas that were tilted in a similar manner, which were also quite visible in the bastion (see Figure 6C). Additionally, the set of tilted domains defined the zones in which vertical-axis folds developed; these were very visible both in the wall near the bastion and southwards. This set of folds can be characterized in several ways and through various classical GIS algorithms, such as topographic profiles (Figure 6D), slope (Figure 6E) or aspect (Figure 6F). Based on the several obtained models, these vertical folds that developed on the city wall range between 11 and 6 m in wavelength, with maximum amplitudes of c. 30 cm and a minimum of only 9. It is worth noting that the axial trace of the folds was not rectilinear (Figure 6C), and the axial plunge (inclination direction of the fold axis) varied along the studied area, from eastward in the northernmost sector of the city wall to westward towards the south (Figure 6D). The axial plunge was also different for both sets of folds, in the range of 81-78\({}^{\circ}\) for the northernmost ones and of 82-88\({}^{\circ}\) for the southern ones.  
In regards to the tilted segments in the bastion (north segment of the study area), it is remarkable how a detailed analysis of the hyposymetric distribution (highlighting the tilted domains of the wall with similar dips) and slope over a very detailed DEM (1 mm pixel) allowed the identification and mapping of the exact fractures responsible for resolving the deformation with extreme precision (Figure 7).