资源环境科技发展态势分析平台

Asperities are patches where the fault surfaces stick until they break in earthquakes. Locating asperities and understanding their causes in subduction zones is challenging because they are generally located offshore. We use seismicity, inter‐ and co‐seismic slip, and the residual gravity field to map the asperity responsible for the 2014 M8.1 Iquique Chile earthquake. For several years prior to the mainshock, seismicity occurred exclusively downdip of the asperity. Two weeks before the mainshock, a series of foreshocks first broke the upper plate, then the updip rim of the asperity. This seismicity formed a ring around the slip patch (asperity) that later ruptured in the mainshock. The asperity correlated both with high inter‐seismic locking and a circular gravity low, suggesting that it is controlled by geologic structure. Most features of the spatiotemporal seismicity pattern can be explained by a mechanical model in which a single asperity is stressed by slab pull.