The subduction zone along southern Peru and northern Chile is one of the most earthquake-prone subduction zones. It has experienced many >M8 large earthquakes in the past millennia, yet a key segment, the Arica gap, has not ruptured since the 1800s. Understanding how this region is deforming between earthquakes helps assess future earthquake hazards. We use a decade of radar satellite observations (InSAR) from 2014 to 2025 to measure ground motion across 2,500 km of the South American plate interface. This data reveals patterns of landward movement and uplift that vary along the coast, indicating varying velocities of loading of the subducting slab.

To better understand these processes, we use a physical model of the subducting slab and a statistical Bayesian inference method to estimate the distribution of slip velocity along the 2500-km-long plate interface. Our results offer a clearer picture of where strain is accumulating, which can provide clues about the mechanical properties of the subducting slab, how it interacts with the topography on land, and understand the potential for future large earthquakes that may occur along the subduction zone.