## 5 Structural Interpretation--Discussion
### Insight into the Paleostress Analysis from Previous Approaches
 & **N (Appendix A)** & **SS** \\ \hline T1 MF & 18 & 144\({}^{\circ}\)–03\({}^{\circ}\) & 014\({}^{\circ}\)–86\({}^{\circ}\) & 234\({}^{\circ}\)–03\({}^{\circ}\) & 0.46 & SS & 14.6\({}^{\circ}\) & 16 & 46, 50, 52, 69, 72, 77, 78, 77, 87, & **(6), S57 (6)**, & **S57 (6)**, & **S57 (6)**, & **S59 (7)**, & \\  & & & & & & & 91, 92 & SS11 (3) \\ T2 MF & 19 & 321\({}^{\circ}\)–88\({}^{\circ}\) & 196\({}^{\circ}\)–01\({}^{\circ}\) & 106\({}^{\circ}\)–02\({}^{\circ}\) & 0.60 & PE & 12.6\({}^{\circ}\) & 19 & 38, 40, 52, 54, 59, & **(4)**, S56 (2), & \\  & & & & & & & & 66, 70, 74, 75, 80, & **S57 (9)**, & \\  & & & & & & & & 86, 89, 90, 91 & **S511 (4)** & \\  & & & & & & & & 1, 9, 17, 19, 23, 28, & & \\ T3 MF & 22 & 263\({}^{\circ}\)–04\({}^{\circ}\) & 105\({}^{\circ}\)–86\({}^{\circ}\) & 353\({}^{\circ}\)–02\({}^{\circ}\) & 0.84 & SS-TRN & 14.2\({}^{\circ}\) & 21 & 60, 62, 63, 65, 68, & **(7)**, S56 (2), & \\  & & & & & & & & 73, 75, 76, 82, & **S57 (9)**, & \\  & & & & & & & & 90 & SS11 (2) \\  & & & & & & & & 3, 4, 5, 7, 8, 9, 10, & & **S52 (11)**, S53 \\  & & & & & & & & 12, 13, 15, 16, 18, & & \\  & & & & & & & & & 60, 62, 63, 64, 65, & & \\  & & & & & & & & 70, 82, 83, 84, 85 & & \\  & & & & & & & & 3, 4, 21, 22, 29, 35, & SS2 (2), SS3 \\ T5 MF & 17 & 202\({}^{\circ}\)–13\({}^{\circ}\) & 304\({}^{\circ}\)–41\({}^{\circ}\) & 098\({}^{\circ}\)–45\({}^{\circ}\) & 0.16 & & 15.1\({}^{\circ}\) & 17 & 38, 47, 48, 49, 53, & **(4)**, S56 (4), & \\Any resolved site stress tensor calculated mathematically with a best-fit stress inversion software results in a specific combination of fault activations. As a result, it is not only the stress regime, but also the fault activations that should be geologically reasonable and plausible. Are these fault activation combinations similar when determined by different software? As shown in Figure 5 of [32], in the SS3 station (3--N of Palo), the Andersonian and non-Andersonian tensors, T1 and T2, respectively (as derived using FSA), are grouped in the same event B, whereas with Win-Tensor software, the resolved stress tensors have been grouped differently due to different fault combinations. In a more detailed inspection of the above-mentioned best-fit stress tensors, it is evident that they can be either Andersonian or not, considering if the steepest plunging principal stress axis plunges \(\geq 65^{\circ}\) or not, respectively (cf. [86]). Nonetheless, in most cases, the non-Andersonian stress tensors have their greatest or least principal stress axes in a (sub)horizontal position. An explanation for this is that the four components of the reduced stress tensor are defined using best-fit algorithms simultaneously but independently from one another, and without having any physical, and therefore, geological constraints or limitations concerning the position of the principal stress axes. However, non-Andersonian stress tensors can be falsely resolved from fault-slip data if the latter are heterogeneous [85] or mixed in kinematics, i.e., dip-slip (thrust or normal), oblique, and strike-slip faults  
Figure 5: Tectonic setting of the Central-Western Mediterranean (based and modified from [45]) and paleostress reconstruction of the Ligurian Alps (NW Italy) (red square) since the Late Eocene, considering the \(50^{\circ}\) counterclockwise rotation that occurred in Early–Middle Miocene [32, 69]. (**a**) T1 TRM (restored) (**b**) T2 TRM (restored), (**c**) T4 TRM, and (**d**) T5 TRM. Explanation: \(\alpha_{1}\) and \(\alpha_{3}\) axes are shown with convergent and divergent arrows, respectively. driven by transprssional _s.l._ stress regimes. It is worth noting that in TRP or TRN, where R \(\leq\) 0.125 and R \(\geq\) 0.875, respectively [79], it is not important which of the two principal stress axes is in a vertical position, since their magnitudes are very close, if not equal, making it trivial as to whether the resolved stress type is Andersonian or not.