## 3 Results
### The Mattinata Fault Case Study  
The seismically-active Mattinata fault (MF) outcrops for over 40 km in the Gargano Promontory, Puglia region of southern Italy. It shows an undulated trajectory that is characterized by a number of significant tectonic-related morphological features, compatible with general, long-lasting, left-lateral strike-slip kinematics, although a present-day right-lateral activity has been detected by the focal mechanism solution of an earthquake along this fault [80]. These features include a pull-apart basin and a transgressional zone. In Figure S1, we redraw the geological map of MF given in [59], marking the pull apart basin and transgressional sector in yellow and blue, respectively. The authors analyzed the cleavage sets of the MF and established a number of geometrical and kinematic relationships between the fault and the associated cleavage system. They found that the main associated cleavage consists of a marked array of disjunctive, spaced pressure-solution surfaces developed within the 200-300 m wide fault damage zone that is bounded by unfractured wall rocks. The cleavage-fault angle is almost constantly equal to 40\({}^{\circ}\). It slightly increases in the pull-apart basins and decreases in the transgressional segment. Figure 4: The Pernicana fault, at Piano Pernicana, Mt. Etna (Italy), redrawn after [79]. (**A**) Map of the PF [77]. White arrows indicate the horizontal displacement vectors as measured by [77] between 2005 and 2006. The top picture (taken in 2013) shows visible damage produced by the continuous fault movement to man-made structures. (**B**) Ground motion polarization of each station obtained through the covariance matrix analysis, represented by rose diagrams (in red and blue to the north and south of the fault, respectively). (**C**) Fracture cleavages in the two sides of the PF fault, modeled by using the FRAP package [59]. (**D**) Comparison between fracture strike (black rose diagrams) modelled for the two sides of the fault and the horizontal polarization (red and blue rose diagrams to the north and south of the fault, respectively), highlighting a transversal relationship in the two sides of the PF. Considering the high number of structural investigations performed in the above cited study, this fault was chosen to apply the study of wavefield polarization using ambient noise records [81]. Ambient vibrations were recorded at about 30 sites chosen (at a duration between 20 and 50 min) in the fault damage zone, close to available structural geological measurements at rock outcrops. The stations were equipped with a high-dynamic seismic digitizer (Reftek 130) and a three-component sensor with an eigenperiod of 5 s (Lennartz LE-5s). All measurements were performed according to SESAME (Site EffectS assessment using Ambient Excitations [[http://sesame.geopsy.org/SES_Home_Description.htm](http://sesame.geopsy.org/SES_Home_Description.htm)]([http://sesame.geopsy.org/SES_Home_Description.htm](http://sesame.geopsy.org/SES_Home_Description.htm)), last accessed 16 April 2023) guidelines. The tendency of ground motion to be polarized in the horizontal plane was evaluated in the frequency domain through rotated HVSR (see Section 1) using Geopsy software [82] ([[http://www.geopsy.org](http://www.geopsy.org)]([http://www.geopsy.org](http://www.geopsy.org)), last accessed on 19 April 2023), after applying an anti-trigger algorithm, to select the most stationary part of the signals [82]. The results are given as rose diagrams in Figure S1 for some exemplificative sites. In Figure S2, we also show the contour plots of the HVSR amplitudes. An ambient noise measurement was performed close to the permanent broadband station of the Italian Seismic Network MSAG. The HVSR obtained on ambient noise (Figure S2) were found to be consistent with those inferred on earthquake records [83], both in terms of the amplified frequency band (broadband from 2 to 8 Hz) and in terms of the direction of maximum amplification (roughly NNE-SSW).