Low‐angle extensional shear zones, which often characterize the brittle–ductile transition of continental crust, are seen here to result from strain localization. The potentially destabilizing deformation mechanism is assumed be progressive transformation fractured coarse feldspar grains into white mica as observed in East Tenda Shear Zone, Alpine Corsica. coupling between microfracturing and feldspar‐to‐mica reaction coeval with localization that occurred field case at a depth close 15 km....

Abstract Numerical examples are given which illustrate the poor performance of conventional finite elements in problems involving strain localization frictional materials. In one cases investigated, that granular media subjected to plane biaxial loading, isoparametric seen inhibit altogether. With these by way motivation, a recently proposed element method context materials is assessed, with particular emphasis on three‐dimensional problems. passing, some issues pertaining post‐bifurcation...

We analyze the mechanical properties needed to account for large shallow slip during 2011 Tohoku‐Oki earthquake and activation of landward normal faulting within forearc. show that morphology internal structure forearc follows closely prediction critical Coulomb wedge in horizontal compression, implying a high pore pressure ratio ( λ =0.7+0.14/−0.48) low effective basal friction ). then fault requires lower beneath outer than inner μ ≤0.015), possibly due transient dynamic weakening...

The main objective is to determine the three stages of life a thrust in an accretionary wedge which are onset thrusting along its ramp, development with construction relief, and arrest because another event. A simple kinematics proposed for geometry developing fold based on rigid regions separated by velocity discontinuities work dissipated according Coulomb criterion. evolution satisfies mechanical equilibrium optimized at every time provide least upper bound tectonic force maximum strength...

The very low water content of the granulitic unit Holsnøy, in Bergen Arcs, Norway, caused its partial metastable preservation throughout Caledonian burial end exhumation, leading to observed mixture completely eclogitized and uneclogitized rocks. eclogitization granulite-facies protolith led a density increase ∼10%, but also large rheological weakening that resulted localization all deep ductile deformation eclogite fraction. We address consequences on subduction dynamics concomitant...

SUMMARY A triangular wedge, composed of a frictional material such as sand, and accreting additional at its front, is the classical prototype for accretionary wedges fold‐and‐thrust belts. simplified method proposed to capture internal deformation this structure resulting from large number faulting events during compression. The combines application kinematic approach limit analysis predict optimum thrust‐fold set geometrical rules update geometry accordingly, each increment shortening. It...

The objective is to demonstrate that the equilibrium element method (EEM) provides stress distribution in geometrical models of folds, relevant fold‐and‐thrust belts as well accretionary wedges. core method, inherited from limit analysis, search for an optimum field (1) equilibrium, (2) remains everywhere below or equal maximum strength rock, and (3) balances largest possible applied tectonic force. This force associated are interpreted those at onset rupture. makes no appeal rock rheology...

Low‐angle midcrustal ductile shear zones and the related microseismic activity recorded below regions of active extension are seen here as two consequences strain localization. The feldspar‐to‐mica reaction which occurs once feldspar grains fractured is destabilizing mechanism selected to explain model problem considered substantiate these claims solved by numerical means combines simple due rigid gliding upper crust (at velocity V s ) stretch resulting from whole e ). rheological accounts...

The evolution of a compressive frictional wedge on weak, and planar décollement, subjected to frontal accretion, is predicted with two step method called sequential limit analysis. first consists in finding, the kinematic approach analysis, length active décollement dips emerging ramp conjugate shear plane composing thrust fold. second leads modification geometry, first, because fold development due compression and, second, erosion. Erosion removing periodically any material above fictitious...

Abstract Finite elements with embedded shocks are used to investigate transient strain localization phenomena in frictional solids. In particular, we seek elucidate the effect of rate sensitivity and inertia on development shear bands solids subjected impulsive loading. As static case, our results show that banding may induce severe softening specimen even as material steadily hardens. expected, retards onset structural tends stabilize post‐peak response. It is verified solution indeed...

Folding of sedimentary layers is often accommodated by the opening or sliding inherited and new discontinuities which are assumed here to be diffuse so that a continuum description applies at fold scale. The rock rheology then described with an elastoplasticity model for permanent deformation simple shear (sliding) dilation (opening) respect specific orientations discontinuities. To illustrate relation between folding activation discontinuities, three‐dimensional layer under compression in...

Abstract The northwestern part of Holsnøy island, in the Bergen Arcs, Norway, consists a granulite-facies protolith partially transformed at depth eclogite (700 °C, > 19 kbars) and amphibolite (650 8–10 facies during Caledonian orogenesis. Eclogitized zones are mainly planar objects (fractures with parallel reaction bands cm-to-100 m-scale shear zones). Eclogitic distributed two sets orientations associated deformation can be described as ‘bookshelf tectonics’. major strike around N120...