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

causing widespread destruction and a pan Pacific tsunami. While there are historical records of other large earthquakes in this rupture zone, they might represent smaller, non-tsunamigenic events within a seismic supercycle (e.g., Goldfinger et al., 2013), emphasizing the need for paleotsunami investigations to understand long-term recurrence patterns. Recent studies have pointed out the existence of a “tsunami gap” in north-central Chile (Easton et al., 2022), where a large tsunami has not been recorded since 1730 C.E., coupled with an incomplete geological record of paleotsunamis during the Upper Holocene (Dura et al., 2015). This study focuses on paleotsunami record in the La Ligua and Petorca river mouths areas, due to the favorable sedimentary environments for tsunami deposit preservation. The research aims to determine the occurrence of ancient tsunamis linked to mega- earthquakes in the Chilean coast (32°24´50´´S), south of the 2015 Illapel earthquake (Mw ~ 8.3) rupture zone. A multidisciplinary approachcombininggeomorphology, sedimentology, geochronology, geochemistry, archaeology, and history is employed. M E T H O D O L O G Y Detailed geomorphological mapping was performed using satellite imagery, Google Earth Pro, aerial photographs, and a digital elevation model (DEM) from drone photogrammetry. Morphological units were classified based on their sedimentary environments, including littoral, estuarine, fluvial, aeolian, and anthropogenic features. Sedimentary facies analysis was performed from surface sediment samples, and from 21 trenches excavated in the La Ligua River floodplain. Facies were defined based on sedimentological, chemical, mineralogical, magnetic, and biological characteristics, and grouped into six assemblages. Radiocarbon dating and archaeological assemblages were used for age determination. Fig. 1: Location of La Ligua and Petorca rivers mouth in central Chile, and eastward view showing the geomorphological situation of the study area.