## 7 Discussion  
The lichenometric analysis developed in this paper indicates a high sensitivity of LGR to the position (vertical/horizontal) and geographical orientation of the exposed rocky surfaces. This occurs at short distances (6 km maximum), and even in the same location, a cemetery in our case (Figures 9 and 10). As it was expected, horizontal populations of lichens display larger LGR, than the vertical ones, but these last are the most suitable ones for the chronological analysis of the vertical bedrock scarp of the Sencelles Fault. Among the differently oriented vertical lichen populations, those facing the NW, like the bedrock fault scarp, resulted in the most appropriate for this study (Figure 12). Eventually, only the vertical populations (facing NW) of the cemeteries of Sta. Eugenia and Sencelles, located on the fault trace (Figure 2), were used to calculate the LGR of the two lichen species used in this study (Figure 12). In both cases, mean growth rates for _A. calcarea_ (0.22-0.23 mm/yr) were always higher than those for _A. radiosa_ (0.16-0.19 mm/yr) (Figure 11; Table 1). Mean LGR for the vertical datasets of _A. calcarea_ and _A. radiosa_ indicated that the differentially colonized ribbons of the basal fresh scarp (Figure 8) have a historical age as old as the early 16 th century (Tables 2 and 3). On the contrary, the upper rugged section of the scarp was largely colonized by black lichen colonies overlapped by the orange crustose lichen _X. calcicola_ and by large coalescent colonies of _A. calcarea_ unsuitable for lichenrometric analysis. As indicated by the survival time of lichen colonization in limestone surfaces before flaking at 700-800 years [7, 31], this upper segment of the scarp may have an age predating the 12 th century. However, considering its weathering stage (solution pits), scarp retreat (78 cm), and scarp angle (45-75\({}^{\circ}\)), this scarp segment should have a Holocene age probably older than 3500 years before the present (Figure 8). As mentioned in Section 5, the obtained ages for the older ribbon (B3) of the basal historical scarp are near the range of the first strong earthquake documented on the island: the 1721 CE earthquake (VII EMS-VIII ESI07) near the locality of Selva [36], 12 km north of the fault scarp (Figure 1). This is a doubtful seismic event, recently characterized as a giant mass-movement event by some authors (Biniarroi complex landslide) [39]. This large avalanche affected an area of 296,000 m\({}^{2}\) and mobilized more than 2 million cubic meters of poorly consolidated Plio-Quaternary materials, generating a high variety of ground failures and hydrogeological changes [39]. The event affected several houses in the small village of Biniarroi and it was felt at Selva as a large tremor [23-25]. In the case of a coseismic landslide, their huge dimensions will indicate a minimum local intensity of VIII ESI07 [40]. Whatever the case, this event is still cataloged as an intensity VII EMS earthquake in the official seismic databases of Spain [36]. These same catalogs list other smaller earthquakes (IV-V EMS) in the environs of Sta. Maria del Cami and Sencelles between the years 1763 and 1773 CE (Figure 1), also within the range of the computed age for ribbon B3 (Figures 8 and 10). These two last historical events have their macroseismic epicenters near the locality of Sencelles (Figure 1) and they can be related to the activity of the SCF but not to any of the studied ribbons or trench units. However, the dimensions of the third ribbon of the scarp B3 (c. 70 cm) preclude its correlation with any of the mentionedevents, suggesting instead a prehistorical age for the causal event. The colluvial wedge of Unit C is the oldest one (Figure 12). This unit is free of _terra-rossa_, strongly cemented, and displays littoral features impossible to corelate with the obtained lichenometric ages (c. 1700 CE) of the basal fresh fault plane (Tables 2 and 3).