Long-Term Interactions Between Intermediate Depth and Shallow Seismicity in North Chile Subduction Zone

We document interactions between intermediate depth and interplate seismicity in the North Chile subduction zone, over a 25 year period (1990-2015). We show that the 2005 M-w 7.8 Tarapaca slab-pull earthquake was followed by 9 years of enhanced deep and shallow seismicity, together with the decrease of eastward average GPS velocities and associated interplate coupling, eventually leading to the 2014 M-w 8.1 Iquique megathrust earthquake. In contrast, megathrust ruptures (e.g., M-w 8.0 Antofagasta in 1995, or M-w 8.1 Iquique in 2014) initiate several years of silent background seismicity in the studied area, both at shallow and intermediate depths. The plunge of a rigid slab into a viscous asthenospheric mantle could explain the observed synchronization between deep and shallow seismicity and their long-term interactions.