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

24 PATA Days 2024 Fig. 3: a) Dendrochronological sampling site close to the trench excavation site and a cut-section of the tree in the upper-left picture. b) View of a 2 meters-wide sag-pond parallel to the strike of the fault, and filled with water. C O N C L U S I O N S Until now, surface ruptures associatedwith the 1949 earthquake had only been described in Argentina territory, to the east of Lake Fagnano (Costa et al., 2006; Pedrera et al., 2014; Roy et al., 2020; 2023). Roy et al. (2020) indicate that the rupture stopped to the east before reaching the Atlantic Ocean. The total length of ruptures that have been mapped west of Lake Fagnano barely exceeds 50 km, which is small considering the estimatedmagnitude. This study is the first to reveal surface ruptures associated to the 1949 earthquake in Chilean territory, 100 km east of the western shore of the Fagnano Lake, indicating that the total rupture length exceeded 150 km. Surface rupture in Chile is discontinuous, generating multiple segments, with lengths typically not exceeding 2 km, yet running parallel to each other. Although the fieldwork evidence does not allow for direct estimations regarding the strike- slip offset of the fault in the area, the vertical offset showing an apparent uplifted block situated either on the northern or southern side of the fault, depending on the topographic slope, indicates that horizontal motion was the main slip component on superficial faults. Finally, it is interesting to note that numerical simulations of co-seismic deformations resulting from the 1949 earthquakes indicate subsidence of the southern block close to the western termination of rupture (Mendoza et al., 2022). Then, the subsidence of the Betbeder River delta evidenced by the sunken forest may be related to the western end of the 1949 rupture.