Abstract

The 2015 MW 8:3 Illapel earthquake shook Chile on September 16, 2015, and was fol17 lowed in the remaining weeks by very dierent responses from Nevados de Chillan, Co18 pahue, and Villarrica volcanoes, all located on the earthquake far-eld, more than 580 19 km away. Here we show how Nevados de Chillan and Copahue started new eruptive phases 20 in the weeks and months following the Illapel megathrust, and a new magma intrusion 21 process was halted at Villarrica. These were the only 3 volcanoes that were in an altered 22 state before the mainshock. Using seismic, geodetic, and geochemical observations, in 23 combination with numerical wave propagation simulations, we also show that the geom24 etry of the fault system controlled the impact of the earthquake on each volcano. We 25 argue that the sensitivity of a volcano towards an earthquake depends on both the vol26 canic state before the mainshock and the geometry of its fault system. This is a case where 27 the same earthquake generates very dierent responses at the same time, at large dis28 tances, which renders volcanoes as very sensitive systems.