Three‐Dimensional Variation of the Slab Geometry Within the South American Subduction System

Abstract

AbstractSubduction of the Nazca plate results in the uneven distributions of earthquakes and arc volcanoes along the South America's western margin. Here, we construct a high‐resolution shear‐wave velocity model from immediately offshore to the backarc in South America, using advanced full‐wave ambient noise tomography. Our new model confirms and provides further constraints on three major features, including (a) extensive low‐velocity anomalies within the continental crust, (b) two high‐velocity flat slab segments located beneath southern Peru and central Chile, and (c) complex slab geometry at flat‐to‐normal transitional subduction. The flat slab segments roughly correlate with the volcanic gaps but not with the seismicity gaps. We suggest that variations of slab geometry along strike and down dip have significantly modified the flow patterns within the mantle wedge. Subduction of oceanic ridges has altered the slab dehydration processes, which can influence the distribution of arc volcanism and the occurrence of intermediate‐depth earthquakes.