Intraplate stress state from finite element modelling: The southern border of the Spanish Central System

Abstract

An elastic finite element approach has been used with the dual aim of determining the most appropriate reference state of stress, namely a uniaxial strain state or a lithostatic state, and refining the understanding of the Iberian intraplate stresses. A cross-section model with an average crustal rheology and a flat topography has been analysed first in order to evaluate the influence of boundary conditions and rheological properties in the reference and tectonic stress states. The uniaxial and lithostatic states are obtained by including the overburden weight and a compressive horizontal load, which equals the uniaxial and lithostatic stress respectively, and provided that Poisson's ratio equals ~ 0.5 in the lithostatic state. On the other hand, a tectonic state with a σ H > σ V regime is reproduced by adding a horizontal constant load. Subsequently, constraints on the magnitude of the predicted Cenozoic stresses along a NW–SE cross-section in the southern border of the Spanish Central System (in the Variscan granitic basement of El Berrocal) have been estimated incorporating the topographic loading, lithological variations and the most recent far tectonic stresses. The deep geological structure has been established from gravity modelling and geological data. To simulate the active strike-slip to uniaxial extension regimes in the interior of Iberian Peninsula, a lithostatic initial state has to be considered and a tectonic load in the range of 15–20 MPa has to be applied. The gradient of maximum horizontal stress originated under these conditions is in the range of 30–35 MPa km − 1 . These results are in accordance with the estimated intraplate tectonic stress, the force along the convergent plate boundary of Eurasia–Africa, the lithospheric strength of Iberia, and the direct measurements of stresses.