When crust thickens during crustal shortening, the underlying mantle lithosphere must shorten and thicken also, causing submersion of cold, dense material into surrounding asthenosphere. For a range physical parameters thickened boundary layer that forms transition from strong to convecting asthenosphere may become unstable, detach, sink asthenosphere, be replaced by hotter asthenospheric material. We have studied instability for (Rayleigh number), amounts thickening, conditions. In all...

Numerical experiments on a thin viscous sheet model for deformation of continental lithosphere subjected to an indenting boundary condition yield distributions crustal thickness, stress and strain rate, latitudinal displacements that may be compared with observations in the India‐Asia collision zone. A simple applied initially laterally homogeneous sheets obeying power law rheology produces results are broad agreement observations, provided exponent is three or greater can support vertically...

The Tibetan plateau is the product of crustal thickening caused by collision between India and Asia largest active example extensional tectonics in a zone continental collision. Throughout most Tertiary, were dominated north‐south shortening, significant proportion which took place on east‐west striking thrust faults. For last 5 m.y. or so has been thinning mechanism extension trending normal Previous investigations have able to account for large‐scale features Tertiary deformation but...

Continental convergence results in compressional deformation over a distance, perpendicular to strike, that is comparable the length of convergent boundary. The forces generated by are resisted, some extent, extensional deviatoric stresses arising from isostatically balanced increases crustal thickness; as result plateau may form, front boundary, whose elevation limited strength continental lithosphere. However, do not exceed generate crustal-thickness contrasts unless there major change,...

The growth of the gravitational instability associated with a dense layer overlying lighter layer, Rayleigh–Taylor instability, depends strongly on constitutive law relating stress and strain rate. We analyse to understand how dependence viscosity might affect convective thickening cold, lithosphere beneath mountain belts. bottom material, attached rigid boundary above it fluid negligible viscosity, is swept into drips or blobs descending material thins elsewhere. Numerical calculations for...

A finite element method is used to calculate stresses and strain rates in a thin viscous sheet, representing the continental lithosphere, that bordered one part by an indenting boundary. We solutions for velocity fields, crustal thickness distributions, rates, rotation (time‐integrated vorticity), ellipsoids show dependence of these quantities on controlling parameters: stress‐strain exponent n strength sheet relative gravitational forces (which may be expressed as dimensionless number:...

Since the beginning of continental collision between India and Asia there has been about 2500 km convergence, northward movement accommodated by major internal deformation Asian lithosphere. The crustal thickening in around Tibetan Plateau is clearly a direct consequence this collision, but considerable debate as to whether large fraction indentation eastward motion lithospheric blocks southeastern southern China. Numerical experiments described here test hypothesis for range geometries...

Convection in the upper mantle can give rise to normal stresses on base of continental lithosphere that may cause localized elevation its surface and extensional deviatoric stresses. This possibility is investigated assuming homogeneous, biaxial strain a whose strength governed by combination brittle failure power law creep crust brittle, law, or Dorn behavior mantle. For given geotherm for rheologies based current laboratory data, responds convection‐induced uplift one three ways, depending...

We analyse receiver functions from 29 broad‐band seismographs along a 380‐km profile across the Longmenshan (LMS) fault belt to determine crustal structure beneath east Tibetan margin and Sichuan basin. The Moho deepens about 50 km under Songpan–Ganzi in Tibet 60 LMS then shallows 35 western average Vp/Vs ratios vary range 1.75–1.88 Tibet, 1.8–2.0 LMS, decrease systematically NW part of basin less than 1.70. A negative phase arrival above is interpreted as PS conversion top low‐velocity...

The deformation of a thin viscous layer that has moving boundary is investigated for comparison with zones in the continental lithosphere. Exact analytical solutions, case Newtonian fluid, and approximate fluid power law rheology, show that: When imposed velocity vector normal to (congressional or extensional regime) field decays away from characteristic length scale 1/3 1/10 wavelength distribution n between 1 10, where stress‐strain exponent rheology; contrast, when parallel (transcurrent...

Crustal deformation along the present‐day northern margin of Tibetan Plateau has occurred since mid to late Eocene time, soon after India collided with Eurasia. Assuming that on these distance and time scales lithosphere can be approximated using a thin viscous sheet, we show far‐field lithospheric caused by an indenting boundary is expected start shortly collision begins. When strong region analogous cratonic like Tarim Basin included in calculations, shear vertical strain rates concentrate...

Abstract It is now more than 50 years since Tuzo Wilson published his paper asking ‘Did the Atlantic close and then re-open?’. This led to ‘Wilson Cycle’ concept in which repeated opening closing of ocean basins along old orogenic belts a key process assembly breakup supercontinents. implied that processes rifting mountain building somehow pre-conditioned weakened lithosphere these regions, making them susceptible strain localization during future deformation episodes. Here we provide...

Abstract We estimate the strength of lithosphere in Anatolia and Aegean, boundary forces acting upon it, using a dynamical model that treats as thin fluid sheet deforming response to variations gravitational potential energy. This has one free material parameter, power law exponent, n , vertically averaged rheology lithosphere, two parameters specify per unit length applied its edges. Solutions this best fit velocities 346 reliable GPS sites require an effective viscosity 10 22 21 Pa s at...

The India‐Asia collision has caused crustal thickening in Tibet by at least a factor of 2. In the last 20–30 Myr this Tian Shan mountain range also been reactivated. Tarim Basin, however, shows little internal deformation. We describe series numerical experiments which constrain effective lithospheric strength parameters Basin and context thin viscous sheet model. use finite element representation model to approximate deformation field compare thickness distributions with that inferred from...

Localized mechanical thickening of cold, dense lithosphere should enhance its gravitational instability. Numerical experiments carried out with a layer in which viscosity decreases exponentially depth, overlying either an inviscid or viscous half-space, reveal exponential growth, as predicted by linear theory. As shown earlier for non-linear and constant rheological parameter Houseman & Molnar 1997), perturbation to the thickness grows super-exponentially; variation parameter, time...

A preliminary study of the aftershocks three earthquakes that occurred near to Corinth (Greece) in 1981 is combined with observations morphology and faulting understand evolution Eastern Gulf Corinth. The well located form a zone 60km long 20km wide. They do not lie on main fault planes are mostly between north-dipping which first two south-dipping associated third event. cluster also lies footwall eastern end Morphologically, it observed Corinth, antithetic apparently predates appearance at...

Subducted slab roll-back, lithospheric instability and asthenospheric extrusion have all been proposed as mechanisms that explain the evolution of extensional Pannonian Basin, within convergent arc Alpine–Carpathian mountain system in central Europe. We determine P- S-wave velocity structure mantle to depths 850 km beneath this region using tomographic inversion relative arrival-time residuals from 225 (P waves) 124 (S teleseismic earthquakes recorded by 56 stations Carpathian Basins Project...

Abstract Seismic images of active fault zones can be used to examine the structure faults throughout crust and upper mantle give clues as whether associated deformation occurs within a narrow shear zone or is broadly distributed through lower crust. Limitations on seismic resolution difficulties imaging shallow structures such crust‐mantle boundary (Moho) place constraints interpretation images. In this study we retrieve body wave reflections from autocorrelations ambient noise. The...

Abstract We describe the results of a benchmark study numerical codes designed to treat problems high Prandtl number convection in three-dimensional Cartesian geometry. In addition, quantitative from laboratory experiments are compared with data. The cases bimodal at constant viscosity and square cell for temperature-dependent have been selected.

Abstract In the Archaean, combination of warmer continental geotherm with a lighter sub-continental lithospheric mantle suggests that gravitational forces played more significant role in deformation. To test this hypothesis, we compare evolution deformation and regional state stress ‘Archaean-like’ ‘Phanerozoic-like’ lithospheres submitted to same boundary conditions triaxial stress-field imposed convergence one direction. For plausible physical parameters, thickening normal cold Phanerozoic...