Understanding the long‐term earthquake recurrence pattern at subduction zones requires continuous paleoseismic records with excellent temporal and spatial resolution and stable threshold conditions. South central Chilean lakes are typically characterized by laminated sediments providing a quasi‐annual resolution. Our sedimentary data show that lacustrine turbidite sequences accurately reflect the historical record of large interplate earthquakes (among others the 2010 and 1960 events). Furthermore, we found that a turbidite's spatial extent and thickness are a function of the local seismic intensity and can be used for reconstructing paleo‐intensities. Consequently, our multilake turbidite record aids in pinpointing magnitudes, rupture locations, and extent of past subduction earthquakes in south central Chile. Comparison of the lacustrine turbidite records with historical reports, a paleotsunami/subsidence record, and a marine megaturbidite record demonstrates that the Valdivia Segment is characterized by a variable rupture mode over the last 900 years including (i) full ruptures (M_w ~9.5: 1960, 1575, 1319 ± 9, 1127 ± 44), (ii) ruptures covering half of the Valdivia Segment (M_w ~9: 1837), and (iii) partial ruptures of much smaller coseismic slip and extent (M_w ~7.5–8: 1737, 1466 ± 4). Also, distant or smaller local earthquakes can leave a specific sedimentary imprint which may resolve subtle differences in seismic intensity values. For instance, the 2010 event at the Maule Segment produced higher seismic intensities toward southeastern localities compared to previous megathrust ruptures of similar size and extent near Concepciόn.

Event deposits in lake sediments provide invaluable chronicles of geodynamic and climatic natural hazards on multi-millennial timescales. Sediment archives are particularly useful for reconstructing high-impact, low-frequency events, which are rarely observed in instrumental or historical data. However, attributing a trigger mechanism to event deposits observed in lake sediments can be particularly challenging as different types of events can produce deposits with very similar lithological characteristics, such as turbidites. In this review paper, we summarize the state of the art on event deposits in paleolimnology. We start by describing the sedimentary facies typical of floods, glacial lake outburst floods, avalanches, hurricanes, earthquakes, tsunamis, volcanic eruptions, and spontaneous delta collapses. We then describe the most indicative methods that can be applied at the scale of lake basins (geophysical survey, multiple coring) and on sediment cores (sedimentology, inorganic and organic geochemistry, biotic approach). Finally, we provide recommendations on how to obtain accurate chronologies on sediment cores containing event deposits, and ultimately date the events. Accurately identifying and dating event deposits has the potential to improve hazard assessments, particularly in terms of the return periods, recurrence patterns, and maximum magnitudes, which is one of the main geological challenges for sustainable worldwide development.

Lake sediments contain valuable information about past volcanic and seismic events that have affected the lake catchment, and provide unique records of the recurrence interval and magnitude of such events. This study uses a multi-lake and multi-proxy analytical approach to obtain reliable and high-resolution records of past natural catastrophes from c. 600 year old annually-laminated (varved) lake sediment sequences extracted from two lakes, Villarrica and Calafquén, in the volcanically and seismically active Chilean Lake District. Using a combination of µXRF scanning, microfacies analysis, grain-size analysis, color analysis and magnetic-susceptibility measurements, we detect and characterize four different types of event deposits (EDs) (lacustrine turbidites; tephra-fall layers; runoff cryptotephras; lahar deposits) and produce a revised eruption record for Villarrica Volcano, which is unprecedented in its continuity and temporal resolution. Glass geochemistry and mineralogy also reveal deposits of eruptions from the more remote Carrán-Los Venados Volcanic Complex, Quetrupillán Volcano and the Huanquihue Group in the studied lake sediments. Time series analysis shows 112 eruptions with a Volcanic Explosivity Index (VEI) ≥ 2 from Villarrica Volcano in the last c. 600 years, of which at least 22 also produced lahars. This significantly expands our knowledge on the eruptive frequency of the volcano in this time window, compared to the previously known eruptive history from historical records. The last VEI ≥ 2 eruption of Villarrica Volcano occurred in 1991. We estimate the probability of the occurrence of future eruptions from Villarrica Volcano, and statistically demonstrate that the probability of a 22-year repose period (anno 2013) without VEI ≥ 2 eruptions is ≤ 1.7 %. This new perspective on the recurrence interval of eruptions and historical lahar activity will help improve volcanic hazard assessments for this rapidly expanding tourist region, and highlights how lake records can be used to significantly improve historical eruption records in areas that were previously uninhabited