On 2016 December 25, an Mw 7.6 earthquake broke a portion of the Southern Chilean
subduction zone south of Chiloe Island, located in the central part of the ´ Mw 9.5 1960 Valdivia
earthquake. This region is characterized by repeated earthquakes in 1960 and historical times
with very sparse interseismic activity due to the subduction of a young (∼15 Ma), and therefore
hot, oceanic plate. We estimate the coseismic slip distribution based on a kinematic finite-fault
source model, and through joint inversion of teleseismic body waves and strong motion data.
The coseismic slip model yields a total seismic moment of 3.94 × 1020 N·m that occurred
over ∼30 s, with the rupture propagating mainly downdip, reaching a peak slip of ∼4.2 m.
Regional moment tensor inversion of stronger aftershocks reveals thrust type faulting at depths
of the plate interface. The fore- and aftershock seismicity is mostly related to the subduction
interface with sparse seismicity in the overriding crust. The 2016 Chiloe event broke a region ´
with increased locking and most likely broke an asperity of the 1960 earthquake. The updip
limit of the main event, aftershocks, foreshocks and interseismic activity are spatially similar,
located ∼15 km offshore and parallel to Chiloe Islands west coast. The coseismic slip model ´
of the 2016 Chiloe earthquake suggests a peak slip of 4.2 m that locally exceeds the 3.38 m ´
slip deficit that has accumulated since 1960. Therefore, the 2016 Chiloe earthquake possibly ´
released strain that has built up prior to the 1960 Valdivia earthquake.