Geophysical Research Letters

A double-layered seismic zone in Arica, northern Chile



A double layered seismic zone is determined in Arica, northern Chile using locally recorded events. At depths >100 km two planes of seismicity can be observed: one dipping at ∼30°E with ∼10 km of thickness and a second parallel plane 20–25 km deeper, with the same average thickness. Fault plane solutions for both layers show a wide variability, even between nearby events. The genesis of the Arica double seismic zone seems to be independent of the age, the relative convergence rate and direction of the Nazca plate, because all of these parameters are almost the same along the whole northern Chile and a clear separation of the seismicity into two layers is only observed around the Arica elbow. Moreover, it cannot be responsible of the double layered seismic zone because no similar significant changes are observed in the other well studied double seismic zones.