Characterization of historical megathrust earthquake ruptures in Central Chile using logic tree analysis

Characterizing the spatial distribution of ruptures from historical and recent earthquakes is key to understanding the seismic cycle of large earthquakes in subduction zones, and thus to assessing the potential risks associated with future earthquakes. Central Chile (35 $$^{\circ }$$ ∘ S–38 $$^{\circ }$$ ∘ S) has been repeatedly affected by large earthquakes, such as the 2010 Maule (Mw 8.8) and the 1835 earthquakes witnessed by Robert Fitzroy (HMS Beagle captain). Here, we identify the rupture pattern and tsunami propagation of the 1751, 1835, and 2010 mega-earthquakes, events that overlapped in central Chile, by compiling historical records and applying robust statistical tools. We used an adaptation of a logic tree methodology to generate random sources of slip distribution for each event, constrained by tsunami and vertical deformation data. We find that the three events studied have different slip peaks. The 1751 earthquake has the largest slip with a maximum patch of $$\sim$$ ∼ 26 m, while the 2010 and 1835 earthquakes reach slips of $$\sim$$ ∼ 16 m and $$\sim$$ ∼ 10 m, respectively. Our results show that a part of the margin between 36 $$^{\circ }$$ ∘ S and 37 $$^{\circ }$$ ∘ S was consistently affected by large earthquakes, but with different slip and depth. The shallower depths of the megathrust north of 36 $$^{\circ }$$ ∘ S accumulated energy for at least 300 years, which was released by the 2010 earthquake. Our results provide important constraint for rupture patterns and spatial relationships between historical and recent earthquakes, thus extending the time scale for seismic slip distribution analyses over multiple cycles and contributing to a more comprehensive understanding of seismic hazards.