Continuing megathrust earthquake potential in Chile after the 2014 Iquique earthquake

• Published in: Nature (London) Vol. 512; no. 7514; pp. 295 - 298
• Main Authors: Hayes, Gavin P., Herman, Matthew W., Barnhart, William D., Furlong, Kevin P., Riquelme, Sebástian, Benz, Harley M., Bergman, Eric, Barrientos, Sergio, Earle, Paul S., Samsonov, Sergey
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 21.08.2014; Nature Publishing Group
• Subjects: 704/2151/2809; 704/2151/508; 704/2151/562; Accretion disks; Aftershocks; Analysis; Chile; Earthquakes; Environmental aspects; Forecasts and trends; Humanities and Social Sciences; letter; multidisciplinary; Offshore; Science; Seismic activity; Seismology; Subduction zones (Geology); Tidal waves; Tsunamis; Chile
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature13677

The 2014 Iquique event was not the earthquake that had been expected to fill the regional seismic gap; given that significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, it is likely that future megathrust earthquakes will occur south and potentially north of the 2014 Iquique sequence. 2014 Iquique earthquake examined Two groups publishing in this issue of Nature analyse the seismic context of the Iquique earthquake that occurred off the coast of northern Chile on 1 April 2014 in a seismic zone that had been quiescent since a significant event in 1877. Gavin Hayes et al . identify areas of remaining or elevated earthquake hazard along the megathrust fault in the region, and conclude that the 2014 Iquique event was not the earthquake that had been anticipated. Given that significant sections of the northern Chile subduction zone have not ruptured in almost 150 years, they suggest that it is likely that future megathrust earthquakes will occur south and potentially north of the 2014 Iquique sequence. Bernd Schurr et al . show that the April 2014 earthquake broke a central fraction of the 'northern Chile seismic gap', the last major segment of the South American plate boundary that had yet to rupture in the past century. From July 2013 up to the April earthquake they identify three seismic clusters along this part of the plate boundary, each lasting a few weeks, with earthquakes of increasing peak magnitudes. They conclude that these seismic clusters and their slip transients reflect a gradual weakening of the central part of the seismic gap that was instrumental in initiating the final failure. 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 Chile 3 , 4 , 5 , 6 , which had not ruptured in a megathrust earthquake since a M  ∼8.8 event in 1877. On 1 April 2014 a M  8.2 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, moment tensors, finite fault models, 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 this was not the earthquake that had been anticipated. Significant sections of the northern Chile 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.