The Search for Time-Dependent Coupling Changes on the Plate Interface following the Great Earthquakes of Chile

The increase in space geodetic measurements for examining plate motion in the past three decades has significantly advanced our understanding of complex deformation processes in subduction zones throughout the earthquake cycle. We now recognize a spectrum of seismic and aseismic behaviors, including slow slip events, non-volcanic tremor, low-frequency earthquakes, fault creep, episodic tremor and slip (ETS), postseismic afterslip, and viscoelastic mantle flow transients. Notably, Materna et al. (2019) observed dynamically triggered increases and decreases in plate coupling associated with nearby earthquakes in southern Cascadia. We have reproduced and extended these findings using an improved semi-automated detection method, which reveals additional examples of time-dependent coupling changes in the region. 

This study applies our method to the Chilean subduction zone to investigate similar temporal variability in plate coupling changes. In southern Chile, Klein et al. (2016) and Melnick et al. (2017) documented GNSS velocity increases near the boundaries of the unruptured segments following the 2010 Maule earthquake. GNSS rates south of 21°S accelerate up to 10 mm/year in the second year following the 2014 Iquique earthquake, potentially reflecting a coupling increase (Hoffmann et al., 2018). Additionally, Luo et al. (2020) reported a systematic decrease in seaward velocities from 2010–2019 across the southern half of the great 1960 Valdivia rupture zone. Our ongoing work seeks to detect and characterize such abrupt GNSS velocity changes in Chile using our semi-automated approach and to better understand the underlying physical mechanisms. In particular, we aim to constrain the recently identified phenomenon of dynamically triggered coupling changes, with implications for earthquake cycle models and seismic hazard assessment across global subduction zones.