Proceedings of the 12th International INQUA meeting on paleoseismology, active tectonic and archaeoseismology

212 PATA Days 2024 Osl ages and palaeoseismology We dated single stratigraphic unit of each trench based on post- infrared infrared stimulated luminescence at 225oC (pIRIR225) ages of potassium feldspar. Sample locations are shown in Figures 2, 3, and 4. The ages models were constructed using OxCal (Bronk & Ramsey, 2006). Particularly in the SCF we use a 351 ± 181 ka 21Ne exposure age of Gonzalez et al., (2005) for constraining the beginning of the scarp formation. In all the trenches, we could draw a palaeoseismological evolution in which we distinguished discrete- sudden slip events interpreted as earthquakes as the main control of sedimentation. We based the paleoseimological interpretation on the standard convention that the thickness of the colluvial wedge represents the half of the total coseismic vertical displacement and the empirical relations between coseismic displacement (AD) and magnitude (Mw). In the SCF-1trench, we identified three Mw 6.9-7.0 earthquakes. The first Mw 6.9 earthquake marked the beginning of scarp formation and was related to the event horizon EH1 in Figure 2B. The 21Ne age and the pIRIR225 age of FSCAN5 are the maximal ages for this event horizon. The minimal age of EH1 was defined by the age of FSCAN4 obtained in CW1. The modelled age of EH1 was 100 ± 28 ka and represented a temporal constraint for the beginning of the CW1 accumulation and the age of the first earthquake. A second earthquake was expressed by Figure 4: NGF-2 Trench. A) Logging of the northern wall of trench NGF-2 at the Naguayán Fault. B) Measurements of unit thickness and displacements at the trench. Unit thickness is depicted with black lines. The red solid line depicts the along- dip separation of the AG unit. The red dashed line depicts the along-dip separation conducted by the fault considering the creeping-like displacements. The inset depicts the accumulated net offset of the NGF estimated considering the dip- and strike- slip components estimated from stratigraphic and geomorphic markers, respectively. The acute angle (alpha) corresponds to the rake of the slickenside. C) Detail of the shear bands identified at this trench. Note the change in grain size and orientation of the layers between the shear bands.