Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

Origin of the lithospheric stress field

Abstract: [1] An understanding of the tectonic stress field is geologically important because it is the agent that preserves in the crust a memory of dynamical processes. In an effort to elucidate the origin of the present state of stress of the lithosphere we use a finite element model of the Earth's lithosphere to calculate stresses induced by mantle flow, crustal heterogeneity, and topography and compare these to observations of intraplate stresses as given by the World Stress Map. We explore two models of lithospheric heterogeneity, one based directly on seismic and other observational constraints (Crust 2.0), and another that assumes isostatic compensation. Mantle tractions are computed from two models of mantle density heterogeneity: a model based on the history of subduction of the last 180 Myr, which has proved successful at accurately reproducing the present-day geoid and Cenozoic plate velocities, and a model inferred from seismic tomography. We explore the effects of varying assumptions for the viscosity structure of the mantle, and the effects of lateral variations in viscosity in the form of weak plate boundaries. We find that a combined model that includes both mantle and lithospheric sources of stress yields the best match to the observed stress field (∼60% variance reduction), although there are many regions where agreement between observed and predicted stresses is poor. The stress field produced by mantle tractions alone shows a greater degree of long-wavelength structure than is apparent in the stress observations but agrees very well with observations in some areas where radial mantle tractions are particularly strong such as in southeast Asia and the western Pacific. The stress field produced by lithospheric heterogeneity alone depends strongly on the assumed crustal model: Whereas the isostatically compensated model yields very poor agreement with observations, the model based on Crust 2.0 matches the observations about as well as mantle tractions alone and matches very well in certain areas where the influence of high topography is very important (e.g., Andes, East Africa). A possible interpretation of our results is that the stress field is significantly influenced by lateral variations in the viscosity of the mantle, which leads to variable amounts of decoupling between lithosphere and mantle, allowing the mantle signature to dominate in some areas and the crustal signature to dominate in others. The poor fit between the isostatically compensated crustal model and observations and the large differences between the two crustal models point toward the importance of dynamic topography and remaining uncertainties in crustal structure and rheology. We also consider the possibility that observations of stress from the shallow crust may not reflect the state of stress of the entire plate; stresses in the upper plate may be at least partially decoupled from broader-scale plate driving forces by lateral and vertical variations in lithospheric rheology.

On the Elliptic Inclusion in Anti-Plane Shear

Abstract: In this paper, we consider the anti-plane shear problem of an elliptic inclusion embedded in an infinite, isotropic, elastic medium, subjected at infinity to a uniform stress field. Using complex v...

Fracture permeability and in situ stress to 7 km depth in the KTB scientific drillhole

Abstract: To better understand the mechanisms that control fluid flow and hydraulic conductivity at significant depth in the brittle crust, we have examined the relationship between fracture permeability and in situ stress in the German continental deep drillhole (the KTB main hole) through analysis of high resolution temperature profiles. Our analysis shows that over the entire 3–7 km depth range studied, permeable fractures and faults (i.e., those associated with distinct thermal anomalies) lie close to the Coulomb failure line for a coefficient of friction of about 0.6. This indicates that critically-stressed faults in the crust are also the most permeable faults. This includes a major Mesozoic thrust fault at 7.1 km that is being reactivated as a strike-slip fault in the current stress field. Conversely, non-critically stressed fractures and faults do not appear to be permeable as they are not associated with identifiable thermal anomalies.

Analysis of the South American intraplate stress field

Abstract: The first-order South American intraplate stress field was modeled through a finite element analysis to evaluate the relative contribution of plate boundary forces and intraplate stress sources. The finite element mesh consisted of 3100 nodes in a network of 5993 equal-area triangular elements which provided a spatial resolution of about 1° at the equator. An important aspect of our modeling is the inclusion of topographic forces due to the cooling oceanic lithosphere along the Mid-Atlantic Ridge (e.g., ridge push), the continental margins along the east coast of Brazil and Argentina, and the elevated continental crust (e.g., the Andean Cordillera). Predicted intraplate stresses for two representations of the western collisional boundary forces are evaluated: pinned collisional boundaries and applied collisional boundary forces. Constraint for the modeling was provided by information about the orientation of the maximum horizontal compressive stress, SHmax, provided by 217 stress indicators from the World Stress Map Project as well as by SHmax magnitude estimates and torque information from previous investigations. Our modeling results demonstrate that the first-order features of the observed stress field can be explained with simple tectonic models which balance the torque acting on the plate either with a fixed western margin or drag forces applied along the base of the plate. The predicted intraplate stress field is characterized by a nearly uniform E-W SHmax orientation throughout most regions of the plate, with stress magnitudes generally less than 20 MPa averaged over a 100-km-thick lithosphere. Significant perturbation of this regional stress field occurs in the western part of the plate in response to forces associated with the high topography of the Andes. Although the magnitude of the collisional boundary forces acting along the western margin remains poorly constrained, we estimate a plausible upper bound on the force per unit length acting along the Peru-Chile Trench to be about 2.5 × 1012 N m−1. While some of our models are consistent with a driving basal drag to balance the torques acting on the plate, the magnitude of the drag torque is small compared to the contribution from other sources of stress such as the ridge push force.