Postseismic evolution and megathrust re-coupling revealed by the spatio-temporal distribution of seismicity after the 2010 Maule earthquake

The 2010 Mw 8.8 Maule earthquake is one the largest and the best-instrumented megathrust ruptures worldwide, with extensive seismic and geodetic observations spanning its interseismic, coseismic, and postseismic phases, making it an exceptional case for understanding how a subduction interface relaxes and recouples after a great earthquake. In this study, we investigate the spatio-temporal evolution of seismicity with a focus on moderate-to-large seismic events (M ≥ 6) that occurred between 2010 and 2022 in the northern half of the Maule rupture and analyze how their deformation patterns reflect postseismic stress redistribution. While shallow aftershocks dominated the first two years following Maule, later seismicity concentrated around the margins of the main slip patch, where both afterslip and Coulomb stress changes were greatest. Only three M ≥ 6 earthquakes recorded in this interval generated measurable surface deformation: the 2012 Mw 7.1 Constitución, 2017 Mw 6.9 Valparaíso, and 2019 Mw 6.8 Pichilemu earthquakes. GNSS trajectory modeling combined with InSAR observations were used to characterize their coseismic deformation fields and invert for slip on the megathrust, revealing rupture patches consistent with independent constraints on Maule coupling and coseismic slip. The Constitución earthquake activated a deep asperity down-dip of the Maule high-slip zone, in a region that accumulated stress during early postseismic relaxation; the Valparaíso rupture occurred within a strongly coupled segment north of the Maule rupture that experienced enhanced loading and was preceded by a slow-slip episode; and the Pichilemu earthquake ruptured a shallow zone that underwent rapid afterslip before gradually re-locking. Together, these earthquakes demarcate a decade-long transition from afterslip-dominated deformation to the re-establishment of heterogeneous coupling along the megathrust, revealing that the Maule rupture continued to control regional tectonics long after the mainshock. These findings emphasize that moderate-magnitude events are key markers of ongoing stress redistribution and must be included to fully resolve the postseismic stage of the seismic cycle in one of the most active seismogenic subduction zones on Earth.