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Marinin A.V.,Schmidt Institute of Physics of the Earth | Saintot A.,Ruhr University Bochum
Comptes Rendus - Geoscience | Year: 2012

Two groups of researchers have used the same datasets in order to determine paleostress regimes and the corresponding tectonic phases in the northwestern-Greater Caucasus fold-and-thrust belt. The kinematic indicators were inverted by both groups to determine the magnitude and orientation of the tectonic stresses. The Russian group's method is based on the " structural pattern" that developed under a single stress-strain state in a given rock volume. The French group used a fault slip data inversion. Stress fields reconstructed by both groups show similarities. Because the methods are independent, the paleostress fields may reflect natural processes. The best-expressed paleostress field is a NE-SW compression related to the Late Eocene folding and thrusting event. A stress field that may correspond to the latest tectonic phase of the northwestern-Greater Caucasus is characterized by a NNW-SSE striking pressure axis. Other paleostress fields that span from Late Cretaceous to present-day are also reconstructed by both groups. © 2012 Académie des sciences.

Petrunin A.G.,Helmholtz Center Potsdam | Rogozhina I.,Helmholtz Center Potsdam | Vaughan A.P.M.,Trinity College Dublin | Vaughan A.P.M.,British Antarctic Survey | And 6 more authors.
Nature Geoscience | Year: 2013

At the Earth's surface, heat fluxes from the interior are generally insignificant compared with those from the Sun and atmosphere, except in areas permanently blanketed by ice. Modelling studies show that geothermal heat flux influences the internal thermal structure of ice sheets and the distribution of basal melt water, and it should be taken into account in planning deep ice drilling campaigns and climate reconstructions. Here we use a coupled ice-lithosphere model driven by climate and show that the oldest and thickest part of the Greenland Ice Sheet is strongly influenced by heat flow from the deep Earth. We find that the geothermal heat flux in central Greenland increases from west to east due to thinning of the lithosphere, which is only about 25-66% as thick as is typical for terrains of early Proterozoic age. Complex interactions between geothermal heat flow and glaciation-induced thermal perturbations in the upper crust over glacial cycles lead to strong regional variations in basal ice conditions, with areas of rapid basal melting adjoining areas of extremely cold basal ice. Our findings demonstrate the role that the structure of the solid Earth plays in the dynamics of surface processes. © 2013 Macmillan Publishers Limited. All rights reserved.

Galybin A.N.,Schmidt Institute of Physics of the Earth
Engineering Analysis with Boundary Elements | Year: 2016

This paper presents a system of integral equations for the determination of contact stresses on a part of the boundary of elastic half-space by measured data of displacements on the rest of the stress-free boundary. Inverse problems like this are refereed to as conditionally ill-posed with pronounced dependence of the solution from small perturbations in measured data. The 3D problem formulation is based on spatial harmonic functions. It is proposed to use a Trefftz-type method for the sought harmonic functions based on the radial basis functions to solve the system of integral equations. A synthetic example is presented to illustrate the proposed approach. © 2016 Published by Elsevier Ltd.

Popov A.A.,Helmholtz Center Potsdam | Popov A.A.,Johannes Gutenberg University Mainz | Sobolev S.V.,Helmholtz Center Potsdam | Sobolev S.V.,Schmidt Institute of Physics of the Earth | Zoback M.D.,Stanford University
Geochemistry, Geophysics, Geosystems | Year: 2012

We present a three-dimensional finite element thermomechanical model idealizing the complex deformation processes associated with evolution of the San Andreas Fault system (SAFS) in northern and central California over the past 20 Myr. More specifically, we investigate the mechanisms responsible for the eastward (landward) migration of the San Andreas plate boundary over time, a process that has largely determined the evolution and present structure of SAFS. Two possible mechanisms had been previously suggested. One mechanism suggests that the Pacific plate first cools and captures uprising mantle in the slab window, subsequently causing accretion of the continental crustal blocks. An alternative scenario attributes accretion to the capture of plate fragments (microplates) stalled in the ceased Farallon-North America subduction zone. Here we test both these scenarios numerically using a recently developed lithospheric-scale code, SLIM3D, that employs free surface, nonlinear temperature- and stress-dependent elastoviscoplastic rheology and allows for self-generation of faults. Modeling suggests that microplate capture is the primary driving mechanism for the eastward migration of the plate boundary, while the slab window cooling mechanism alone is incapable of explaining this phenomenon. We also show that the system evolves to the present day structure of SAFS only if the coefficient of friction at mature faults is low (0.08 for the best fit model). Thus, our model provides an independent constraint supporting the "weak fault in a strong crust" hypothesis for SAFS. © 2012. American Geophysical Union. All Rights Reserved.

Brune S.,German Research Center for Geosciences | Popov A.A.,Johannes Gutenberg University Mainz | Sobolev S.V.,German Research Center for Geosciences | Sobolev S.V.,Schmidt Institute of Physics of the Earth
Tectonophysics | Year: 2013

The arrival of a plume head at Earth's continental lithosphere is often considered to be an important factor for continental break-up. However, the impact of plume impingement on strength and duration of a rift remains unclear. In this study, we quantify the mechanical and thermal influence of a plume (i.e. lithosphere erosion) on continental break-up. To do that we apply the three-dimensional numerical code SLIM3D that features realistic elasto-visco-plastic rheology. We model the thermo-mechanical response of a segment of Earth's lithosphere that is affected both by extension as well as plume-related lithosphere erosion in order to evaluate the influence on the overall force budget. We find that lithosphere erosion leads to a moderate lithospheric strength reduction of several TN/m. In a force-limited environment, however, this strength reduction may have strong influence on the timing of continental break-up, or it may even control whether continental break-up takes place at all. Additional reduction of the lithospheric strength is likely due to the massive emplacement of dikes that follows intensive melting within the plume head. © 2013 Elsevier B.V.

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