## 2 Geological Setting  
The EBSZ runs across the Internal Zone of the Betic Cordillera, a mountain belt that resulted from the convergence between the Nubian and Eurasian plates since the late Neogene (Figure 2A) [28; 29]. The Internal Zone is formed by a stack of tectometamorphic complexes formed of Paleozoic, Mesozoic, and Cenozoic rocks that were exhumed during the Paleogene [30; 31]. Subsequently and until the middle Miocene (Serravalian), former thrusts were reactivated as low-angle normal faults under extensional tectonics related to the opening of the South Balearic basin (e.g., [32; 33]). Partly coetaneous with this extension (from the Langhian to the Messinian), an intense magmatic activity took place in this area [34], and Neogene sedimentary basins formed (e.g., Lorca and Fortuna basins) [35]. At the end of the Messinian/beginning of the Pliocene, the tectonic convergence between the Nubian and Eurasian plates under an NNW-SSE regional shortening direction [28; 36; 37], inverted previous Neogene basins, and the Guadalentin Depression formed in an area that was previously uplifted [35; 38; 39]. Furthermore, the NNW-SSE regional shortening direction has not changed in the region since the late Miocene [40], as evidenced by GPS data. The study area is located in the central and northern part of the EBSZ (Figure 2B). There, the Guadalentin Depression is bordered to the north by the Alhama de Murcia fault (AMF) and to the south by the Carrascoy fault system (CAF), NE-SW left-lateral strike-slip faults with a reverse component [41] (Figure 2B). The AMF is divided in four sections from SW to NE according to their geomorphological expressions, seismicity rates and fault zone geometries [42]: (i) G\(\ddot{\text{o}}\)nar-Lorca, a N40E narrow fault zone that ends in a horsetail to the south; (ii) Lorca-Totana, a section with a N60E trend and \(\sim\)2 km wide fault zone where G\(\ddot{\text{o}}\)mez-Novell [43] identifies at least five strands; (iii) Totana-Alhama de Murcia, also with numerous strands, which recovers the N40E trend and loses geomorphological expression (outcrop of fault plane) northeastward; and (iv) Alhama de Murcia-Alcantarilla, where this expression is very diffuse, possibly because the deformation in this sector is transferred to CAF [42]. In turn, the CAF is formed by two overlapping segments [44]. The SW segment is represented by: (i) the Carrascoy fault sensu lato, that uplifted the Carrascoy Range, and (ii) the Algezares-Casas Nuevas fault (ACNF), that runs for 23 km from the villages of Algezares to Casas Nuevas [44,50]. This area was studied by MASW and P-wave tomography, revealing the underground structure, damage zone related to blind faults, and allowed us to propose a vertical slip rate for the Algezares-Casas Nuevas fault of 0.66 \(\pm\) 0.06 m/kyr since 209.1 \(\pm\) 6.2 ka [27]--submitted. The La Torrecilla profile is located in the northern sector of the Gonar-Lorca section of the AMF (Figure 2C). A single strand and 100 m wide deformation shear zone separates  
Figure 2: Geological setting of the study area. (**A**) Geodynamic frame of the study area. Arrows indicate the current approximation direction between Eurasian and Nubian plates. (**B**) Geological and seismological setting of the Eastern Betic Shear Zone (EBSZ); SMF: San Miguel de Salinas Fault; BSF: Bajo Segura Fault; CAF: Carrasco Fault; LTF: Los Tollos Fault; AMF: Alhama de Murcia Fault; PF: Palomares Fault; CF: Carboneras Fault; ACFZ: Alpujarrides Corridor Fault Zone; MF: Las Moreras-Escarpe de Mazarro Fault. Geological mapping was carried out from Continuous Digital Maps at scale of 1:50.000 of the Internal Zones of the Betic Cordillera [45]. Active fault traces are from an updated version of QAFI database [46,47]. Earthquake data correspond to a declustered version of the Spanish national seismic catalog [48]. (**C–E**) represent the locations of Figure 2C–E. Geological setting of the La Torrecilla profile modified from [PERSON] et al. [49]. The blue star marks the position of the scientific borehole FAM-1.