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Abstract:
Between 2010 and 2015 three giant earthquakes occurred in the Chilean subduction where the oceanic Nazca plate plunges under South America. These were the largest events there since the gigantic M9.5 1960 earthquake so their close occurrences raise the question of a possible link between them. We show here that two-and-a-half days after the M8.2 Iquique earthquake, seismic activity started to increase downdip below (depth~100 km) the future Illapel epicenter. This increase, which began with the largest intermediate-depth earthquake in the Chilean subduction after Iquique, lasted until the M8.3 Illapel earthquake, 18 months later. The mechanisms involved suggest that the Iquique earthquake started a tear in the slab directly downdip from the future epicenter. This study relies on seismicity which occurs in the cold core of the slab and which is the only direct information we have on processes occurring at these depths. The results support that giant earthquakes interact at the scale of a subducting plate and suggest that this interaction occurs through the deep slab.
