3D finite element modelling of the central andean subduction zone with realistic geometry

Zeumann, Stefanie GND

One of the most interesting subduction zones on earth is the western margin of Central South America, where the Nazca plate descends beneath the South American Plate. The Andes are the largest active orogen caused by subduction. In this work 3D dynamic models of the Central Andes between 17°S-23.5°S and 60°W-75.5°W are developed with the Finite element Method (FEM). In contrast to earlier finite element models the geometry of the models in this work were derived from a well constrained density model. Convergence velocities were applied to the Nazca and the South America plate. Nearly the whole model shows compressional east-west strain with the highest compression in the Precordillera and Western Cordillera with values up to -0.006 strain. The strain rates calculated from the model results fit quite well to strain rates estimated from geological observations. The calculated east velocity agrees well with GPS measurements. The modelled stress pattern on the descending Nazca plate correlates with the earthquake distribution in the investigation area. The sensitivity of the models to different rheological parameters e.g. density, mantle viscosity and boundary conditions e.g. slab pull on the deformation pattern in the continental crust are investigated. The oceanward curvature of the trench in southern Peru and northern Chile is unique and turned out to have an influence on the deformation patterns.The investigation shows that using density models as basis for dynamic models is an excellent approach for dynamic modelling.

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Zeumann, Stefanie: 3D finite element modelling of the central andean subduction zone with realistic geometry. 2014.

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