Abstract
Current active front of the Central Andes at Mendoza city latitude (32o50ʼ-33oS). Current active front of the Central Andes comprises part of the western piedmont of the city of Mendoza, where more than 800,000 people are established. Despite this, a comprehensive study of active faults mainly as potential seismogenic sources is lacking in this crucial sector of the Andean foreland. The present study attempts to outwit this shortcoming by characterizing the main Quaternary structures and integrating them in a structural-kinematic model developed from three balanced structural cross-sections. The foreland deformation at the study area is characterized by a population of N-S to NNE striking reverse faults, whose detachment level will be located in the Pre Silurian basement, constituting a thick skin thrust front. The series of thrusts, rooted at a 10-11 km-depth detachment, corresponds to Melocoton and Divisadero Largo faults showing surficial expression, and a blind fault called Maure, inferred om the structural-kinematic model. The Maure blind fault transfers shortening to the west-vergent thin-skinned Cerro de la Gloria thrusts, thus forming a triangular deformation zone. According to morphometric features of these active faults, a probable maximum earthquake magnitude ranges from Mw 5.4 to 6.8. Furthermore, strike slip faults with NW-SE strike are cutting Cerro de la Gloria fault system. Results were contrasted with ground data and focal mechanisms of surficial local earthquakes.
Highlights
Current active front of the Central Andes at Mendoza city latitude (32o50ʼ-33oS)
A comprehensive study of active faults mainly as potential seismogenic sources is lacking in this crucial sector of the Andean foreland
The Maure blind fault transfers shortening to the west-vergent thin-skinned Cerro de la Gloria thrusts, forming a triangular deformation zone
Summary
La historia sísmica de la región centro-oeste de Argentina es ampliamente conocida, ya que sismos de gran magnitud han sido reportados desde 1575 en la ciudad de Mendoza (Morey, 1938; Moreiras, 2004; Perucca y Moreiras, 2010). El frente orogénico presenta un intenso neotectonismo que se evidencia por importante fallamiento de los depósitos cuaternarios, lo que indica que la actividad sísmica tuvo lugar en la región durante este período (Costa et al, 2000a, 2000b; Siame et al, 2006; Ahumada, 2006). Si bien las estructuras con expresión superficial han permitido evaluar su potencial peligrosidad sobre la base de parámetros morfométricos, son escasos los estudios de detalle que permiten establecer el grado de actividad de dichas fallas. Existen también fuentes potencialmente sismogénicas que no tienen expresión en el terreno denominadas fallas ciegas, cuya existencia solo es evidenciada mediante métodos indirectos como estudios geofísicos o modelado estructural. La profundidad donde se encuentre la falla será fundamental para establecer los efectos superficiales de los sismos asociados
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