## 3 Methods and Data  
### Structural Analysis of Faults in La Palma  
The study of tectonic stress and strain deformation fields in active zones makes it possible to describe the role of faults within volcanotectonic processes, which are ultimately those that dominate the geodynamics of volcanic eruptions. In order to establish the orientation of the deformation fields generated by the tectonic stresses, it is necessary in such studies to establish the kinematics of the brittle deformation determined by both the seismic and aseismic movement of the faults. One of the most powerful techniques for determining the stress/strain field is the so-called \"fault population analysis\" (FPA) based on the geometry of the fracture and the kinematic markers observed on the plane of the microfracture, assuming that this process is self-affine [24; 25; 26]. Knowledge of the deformation tensors in a tectonically active zone is a necessary tool to establish which faults are preferentially oriented under a tectonic deformation field and, therefore, which are susceptible to being active faults. Generally speaking, the kinematics of the deformation are obtained from the failure plane and the measurement of its striation (Figure 2). This means that it is necessary in the FPA to take field measurements of pairs of fault plane orientation and striation angle data. In the methods used in this work and described below, the Landslide Model [26; 27] and the Straight Dihedral Model [28; 29], the data obtained based on a single fault offer a possible solution to the deformation field. However, at least 5 faults would be necessary to make it possible to obtain a deformation field that allows fracturing models such as [PERSON]'s to be realistically reproduced. In this work, within the fault population analysis (FPA) methods, we  
Figure 1: Geographical and geological setting: (**A**) geographic location of the Canary Islands archipelago; (**B**) location of La Palma island within the Canary Islands archipelago; (**C**) digital elevation model (DEM) of the island of La Palma and the location of the area covered by lava flows from the 2021 Tajogaite volcanic eruption; (**D**) detailed view of the extent of the lava flows and cinder cone of the 2021 Tajogaite eruption. have used the following methods due to their simplicity, their graphic solution, and the fact that they have sufficient kinematic data giving credibility to the results:  
1. The Right-Dihedron Method, RDM, is a geometric and dynamic method for obtaining deformation fields [28; 29]. 2. The Slip Model, SLIPM, is a method for reconstructing paleostresses through stress inversion [25; 27]. Figure 2: Examples of normal faults in La Palma (DEM of La Palma with the photograph location): (**A**) conjugate normal faults affecting pyroclastic deposits (Taburiente volcanic edifice (superior), Barlovento, La Palma); (**B**) slickensides on normal fault plane affecting basaltic lava flows (Bejenado volcanic edifice, Barranco de las Angustias, La Palma). The main method applied in this work is the Slip Model (SLIPM), as it has several advantages over other paleostress reconstruction methods by means of inverse techniques. (a) It obtains a graphic representation that is applicable to the study of the geodynamics of fracturing by spatial distribution (deformation cluster) and (b) it is a direct method that avoids subsequent manipulations that could be mathematical artifacts. SLIPM, in addition, allows the separation of fault subpopulations that are compatible with different maximum horizontal shortening directions (D\({}_{\text{ey}}\)), which defines homogeneous deformation areas that can be related to different geodynamic stages. Furthermore, SLIPM also makes it possible to deduce the movement directions in those faults whose kinematics could not be observed from field data [27; 30].