Patterns of Rupture Directivity of Subduction Zone Earthquakes in Northern Chile

Abstract

AbstractWe perform a systematic directivity analysis of local seismic events west off the coast of northern Chile. An empirical Green's function technique is applied to a selection of events from a time period from 2008 to 2016 in the vicinity of the rupture area of the MW8.1 Iquique megathrust earthquake in 2014. We compute rupture directivity for 293 events of magnitudes between ML 2.6 and ML 5.3. We find a strong preference of rupture orientations subparallel to the convergence vector of the Nazca plate relative to the South‐American plate. The preferred rupture direction is downdip. We speculate that the reason for the dominating rupture direction could be a lateral limitation of available rupture directions by the repeating earthquake‐like nature of the observed events combined with a material contrast at the subduction interface which, according to the bimaterial effect, favors the downdip rupture direction.