Linking offshore morphology and interplate kinematics along the Chilean subduction margin

The coastal morphology along subduction zones is understood to result from the interaction of the megathrust seismic cycle deformation with erosion and sedimentation. The variation of this interplay creates some areas that remain stable and other areas that accumulate permanent deformation over long time scales. However, the link between plate interface kinematics and geomorphology has not been fully explored and therefore a potentially valuable constraint on the long-term seismotectonic segmentation has been neglected. Here, by combining morphometric and statistic analysis with numerical modeling of the transient kinematics (constrained by GPS data along the Chilean margin), we validate that the morphological domains exhibiting conditional stability spatially correlate with locked areas and the rupture extents of recent great earthquakes, and that these domains are primarily related to forearc basins and marine terraces. This correlation, that likely integrates over a time window of several 103 to several 105 years, corroborates that earthquake cycle deformation has a strong imprint on the coastal morphology and that the instrumentally inferred locking has a long term memory across multiple seismic cycles. From this interrelationship we suggest that areas with gentle slopes and that have been identified geodetically as being locked indicate a quiescence process, which can be interpreted as the expression of spatial variations in friction that control the sizes and recurrence intervals of megathrust earthquakes. Our findings reveal that the width of the seismogenic zone is linked to both long and short-term deformations, opening up new avenues for inferring seismic scenarios of a margin by analysing its morphological domains.