Morphology of the Wadati-Benioff zone and volcanismin Ecuador and northern Perú

Abstract

The morphology and parameters of the Wadati-Benioff zone were established on the basis of the distribution of earthquake foci in Ecuador and northern Peru. The existence of an intermediate depth aseismic gap related to active andesitic volcanoes was confirmed in Ecuador and southern Colombia. For the flatly inclined slab an aseismic region in the Wadati-Benioff zone was found and correlated with the occurrence of the Pliocene and Pleistocene volcanism in northern Peru and southern Ecuador. The laterally variable depth of penetration and posible segmentation of the subduction zone appeared to be connected with the hampering effect of major ocean floor elevations and fracture zones of the Nazca plate. The rr.ean rate and the time of beginning of the present cycle of the Andean subduction were estimated.