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

22 PATA Days 2024 similar to the scarps observed in Argentina that formed during the 1949 earthquake; (2) occurrence of tree trunks located above the scarp which are tilted towards the descending block (Figure 3a), and (3) occurrence of small sag ponds, generally 10 meters-long and 2 meters-wide, which are often filled with water (Figure 3b). These may not be preserved nowadays if the associated rupture was very old. From east to west, the first segment close to the border with Argentina, is at least 2 km-long with an azimuth of N100ºE (Figure least five fault segments in the area (Figure 2a) that accommodated recent ruptures, possibly associated with the 1949 earthquake. Faults presenting evidence of recent ruptures are located north of the western part of Lake Fagnano, in the vicinity of Estancia Lago Fagnano. Direct evidences for a recent activity of these ruptures are the following: (1) well-preserved scarps developed within the soft Quaternary cover(including sand and silt-clay soil, moraine deposits and fluvial deposits) which indicates the lack of erosion or degradation, Fig. 2: a) Map showing the location of recent ruptures (red lines) identified on the northern part of Lake Fagnano in Chile. The plus and minus symbology represents positive and negative topography of the scarp, respectively. The reported sunken forest location is shown in this map. b) Mapping of part of the easternmost fault segment, showing detailed geometry and extension of ruptures. The location of one of the sampling sites for dendrochronology and the trench excavation site are shown in this map.