Stress modeling in the Andes: constraints on the South American intraplate stress magnitudes

An elastic finite element analysis of the lithospheric stress field in the Cordillera Blanca region of Peru has been used to evaluate the lithospheric stress state and constrain the South American intraplate stress magnitudes. The modeling results indicate bounds of 10 and 75 MPa for the magnitude of the average horizontal stress averaged over a 100-km-thick lithosphere. A preferred value of 25 MPa is obtained on the basis of fitting all of the data for the rheological models considered and predicting a transition from extension to compression near the 300-m elevation contour. Such a far-field average stress is consistent with a ridge push origin. The effect of incorporating thermal support for the topographic load of the Cordillera Blanca would be to further reduce the estimate of the intraplate stress magnitudes. -from Authors