Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake

Abstract

The seismic gap theory 1 identifies regions of elevated hazard based on a lack of recent seismicity in comparison with other portions of a fault. It has successfully explained past earthquakes (see, for example, ref. 2) and is useful for qualitatively describing where large earthquakes might occur. A large earthquake had been expected in the subduction zone adjacent to northern Chile3–6, which had not ruptured in a megathrust earthquake since aM 8.8 event in 1877. On 1 April 2014 aM8.2 earthquake occurred within this seismic gap. Here we present an assessment of the seismotectonics of the March– April 2014 Iquique sequence, including analyses of earthquake relocations, momenttensors, finite faultmodels,moment deficit calculations and cumulative Coulomb stress transfer. This ensemble of information allows us to place the sequence within the context of regional seismicity and to identify areas of remaining and/or elevated hazard. Our results constrain the size and spatial extent of rupture, and indicate that thiswas not the earthquake that had been anticipated. Significant sections of the northernChile subduction zone have not ruptured in almost 150 years, so it is likely that future megathrust earthquakes will occur to the south and potentially to the north of the 2014 Iquique sequence.