Seismic-afterslip characterization of the 2010 MW 8.8 Maule, Chile, earthquake based on moment tensor inversion

On February 27th 2010, a MW8.8 earthquake struck the coast of south‐central Chile, rupturing ∼500 km along the subduction interface. Here we estimate the amount of seismically‐released afterslip (SRA) and the mechanisms underlying the distribution of aftershocks of this megathrust earthquake. We employ data from a temporary local network to perform regional moment tensor (RMT) inversions. Additionally, we relocate global centroid‐moment‐tensor (GCMT) solutions, assembling a unified catalog covering the time period from the mainshock to March 2012. We find that most (70%) of the aftershocks with MW> 4 correspond to thrust events occurring on the megathrust plane, in areas of moderate co‐seismic slip between 0.15 and 0.7 fraction of the maximum slip (Smax). In particular, a concentration of aftershocks is observed between the main patches of co‐seismic slip, where the highest values of SRA are observed (1.7 m). On the other hand, small events, MW< 4, occur in the areas of largest co‐seismic slip (>0.85 Smax), likely related to processes in the damage zone surrounding the megathrust plane. Our study provides insight into the mechanics of the seismic afterslip pattern of this large megathrust earthquake and a quantitative approach to the distribution of aftershocks relative to coseismic slip that can be used for similar studies in other tectonic settings. Key Points Seismic afterslip occurs mostly offshore in between patches of co‐seismic slip Major aftershocks occur on the megathrust, in areas of medium coseismic slip High co‐seismic slip areas are dominated by small aftershocks