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

34 PATA Days 2024 wall topography and coincide with the footwall surface. The input parameters used directly impact scarp morphology and resulting shortening. Maximum and minimum shortening rates for each unit (Q3, Q4, Q5) were calculated to compare them with bibliographic data and contribute with novel data. For the case of the Q3 level, the maximum shortening obtained by the trishear model was used because the tip point of the fault is located above the topography, observed at the thrust outcrop (Alvarellos et al., 2022). Furthermore, the modeling suggests a hanging wall with excess material that could be deposited at the foot of the thrust once the erosive agents acted on the scarp. The resulting shortening on the horizontal vector is 5.06 meters and considering the fault plane of 28° and the age of the unit of 3.3 ka (Schmidt et al., 2011a), this yields a dip-slip rate of 1.79 mm/yr and a shortening rate of 1.58 ± 0.95mm/yr. The trishear modelling chosen to calculate the dip-slip rate of the Q4 unit corresponds to the maximum given, presenting a tip above the topography which is inferred from what happens at the Q3 level, and also it presents a morphology of the hanging wall coherent with what is seen in the field. For a shortening in the horizontal vector of 10.33 m and an age of 12.6 ka, a ramp angle equal to the Q3 thrust since is the same structure, the result for the dip-slip rate is 0.90 mm/yr and the shortening rate is 0.80 ± 0.14 mm/yr. For the Q5 unit, given the assumptions made for this data, we prefer the average value obtained between the two shortening rates, which is 0.12 ± 0.2 mm/yr, for the last 16-13 ka. These results suggest a variation in the shortening rate of the splays that affect the piedmont. While the data might imply an acceleration in more recent times when considering different alluvial surfaces affected by the same thrust (0.90 mm/yr over the last 12.6 ka and 1.79 mm/yr over the last 3.3 ka), we must account for spatial variations in the movement rate or varying degrees of erosion across different surfaces, which could be influencing the obtained rates. C O N C L U S I O N S The LPTS of the Southern Precordillera shows clear evidence of propagation towards the piedmont, allowing the estimation of shortening rates in each splay. Maximum and minimum shortening rates ranges were calculated using the forward modelling to assess the extreme possible cases, considering dating errors (Q3: 0.63 mm/yr to 2.53 mm/yr; Q4: 0.66 mm/yr to 0.94 mm/yr; Q5: 0.09 mm/yr to 0.12 mm/yr). The most representative values were chosen and with the mean age two dip slip rates and three shortening rates have been calculated through trishearmodeling in threeQuaternary units (Q3, Q4, and Q5). For the Q3 deposits, the dip- slip rate is 1.79 mm/yr and shortening rate is 1.58 ± 0.95 mm/yr; for the Q4 unit the dip-slip rate is 0.90 mm/yr and shortening rate is 0.80 ± 0.14 mm/yr; and for the Q5 level the shortening rate is 0.12 ± 0.2. A C K N O W L E D G E M E N T S The authors thank the National Council for Scientific and Technical Research (CONICET), Universidad Nacional de San Luis, and Strategy II for their funding support.