Early inhabitants along the hyperarid coastal Atacama Desert in northern Chile developed resilience strategies over 12,000 years, allowing these communities to effectively adapt to this extreme environment, including the impact of giant earthquakes and tsunamis. Here, we provide geoarchaeological evidence revealing a major tsunamigenic earthquake that severely affected prehistoric hunter-gatherer-fisher communities ~3800 years ago, causing an exceptional social disruption reflected in contemporary changes in archaeological sites and triggering resilient strategies along these coasts. Together with tsunami modeling results, we suggest that this event resulted from a ~1000-km-long megathrust rupture along the subduction contact of the Nazca and South American plates, highlighting the possibility of M _w ~9.5 tsunamigenic earthquakes in northern Chile, one of the major seismic gaps of the planet. This emphasizes the necessity to account for long temporal scales to better understand the variability, social effects, and human responses favoring resilience to socionatural disasters.

On 16 September 2015, the $Mw$ 8.3 Illapel megathrust earthquake broke the subduction contact of the Nazca plate beneath the South American plate, causing unexpectedly high tsunami waves that strongly impacted the coast along the Coquimbo region in central–northern Chile. Here, we report results from a postearthquake and tsunami survey, evidencing a complex coastal geological response driven by the near coast and near trench seismic patches that ruptured during this event. Systematically, high tsunami run‐ups, up to 10–11 m a.s.l., were measured on the western coast of the Punta Lengua de Vaca Peninsula in front of the near trench rupture patch, whereas tsunami run‐ups up to 5–6 m were measured close to the near coast rupture patch. Detailed measurements conducted in the Coquimbo area revealed tsunami run‐ups systematically higher than 6–6.5 m and up to 7.8 m. Field observations of bleached coralline algae supported by ulterior laboratory experiences were compared with geodetic measurements that evidenced complex and variable alongshore uplift‐subsidence responses of the coast, suggesting a relative consistency with respect to its modern geomorphological configuration. From the analysis of pit dug in the Tongoy area, which was strongly impacted by this last tsunami, we evaluated distinctive sandy layers with benthic foraminifera tests interbedded between alluvial fine sediments, which we interpreted as paleotsunami events dated before 1108 ± 77 C.E., shortly before 1346 ± 50 C.E., and approximately 1473 ± 37 C.E. In addition to the historical massive tsunamis that occurred in 1730, 1877, and 1922 C.E. in central and northern Chile, we interpreted prehistoric tsunamis revealed here as events triggered by large megathrust earthquake ruptures, evidencing the high exposition of these coasts to near fields as well as to distant tsunamis produced along the Chilean subduction margin but also in the pan‐Pacific region.

El terremoto de Atacama del 11 de noviembre de 1922 (Mw 8,5 – 8,6) es el segundo mayor terremoto ocurrido en Chile en el siglo XX. En este trabajo revisamos los depósitos asociados a este evento tsunamigénico y presentamos nuevas evidencias de su registro en la costa del desierto de Atacama. Las evidencias geológicas aparecen de manera muy puntual y heterogénea debido a la escasez de contextos ambientales adecuados para su conservación, destacando el buen potencial de preservación de los campos de bloques en zonas acantiladas. Es probable que grandes eventos tsunamigénicos ocurridos durante el Presente Interglaciar en costas áridas, como la del desierto de Atacama, hayan pasado desapercibidos hasta la fecha, siendo necesarios estudios multidisciplinares y enfocados a escenarios muy concretos para su correcta identificación y análisis.