Scripting High Performance Earth Systems Simulations on the SGI Altix 3700

A Python language scripting interface for optimised numerical software written in C/C++ has been designed to facilitate the rapid development of 3D parallel simulations on the Altix 3700. A recent advance focusing on the extensions implemented within a high performance finite element kernel module is described. Performance issues, measurements and results on the Altix 3700 are presented

The Influence Of Elasticity, Temperature And Fracture On Large Scale Geological Flow

Realistic simulations of earth processes such as faulting, shearing, magma flow, subduction and convection often require the consideration of non-Newtonian Effects such as elasticity and power law creep. As the deformations involved in geological deformation are often large the constitutive relationships must maintain certain geometric terms to ensure that the tensor properties of the model are conserved. A model with such properties is termed as objective. There are a wide range of objective, visco-elasto-plastic models to choose from. The main structural difference between these models consists in the choice of the objective stress rate, e.g. Jaumann, Oldroyd, Truesdell - rates (see Kolymbas and Herle, 2003, for a recent discussion). In this paper we give an outline of a thermo-visco-elastic-plastic model including a discussion of numerical aspects such as the derivation of a consistent incremental form. The viscous part of the deformation involves a combination of both Newtonian and power law creep. Plastic deformations are described by means of a standard Prandtl-Reuss flow rule combined with a von Mises yield criterion. In planetary scale flow modeling the yield criterion is required as a stress limiter during episodic events e.g. in connection with the initiation of subduction. The temperature sensitivity of the viscous deformation is considered by means of an Arrhenius relation involving a pressure dependent reference (melting) temperature. The salient features of the model are first explored by means of analytical and numerical solutions of a simple shear problem for an infinite strip with fixed and prescribed shear velocities on the bottom and top of the layer respectively

Multicycle dynamics of fault systems and static and dynamic triggering of earthquakes

Dynamic simulations of rupture propagation and multiple earthquake cycles for varying fault geometries are presented. We investigate the role of both dynamic and static stress changes on earthquake triggering. Dynamic stress triggering of earthquakes is caused by the passage of seismic waves, whereas static stress triggering is due to net slippage on a fault resulting from an earthquake. Static stress changes represented by a Coulomb failure function and its relationship to seismicity rate change is a relatively well-known mechanism, whereas the physical origin of dynamic triggering remains one of the least understood aspects of earthquake nucleation. We investigate these mechanisms by analysing seismicity patterns with varying fault separation, geometry and with and without dynamic triggering present

Universal and wide shear zones in granular bulk flow

We present experiments on slow granular flows in a modified (split-bottomed) Couette geometry in which wide and tunable shear zones are created away from the sidewalls. For increasing layer heights, the zones grow wider (apparently without bound) and evolve towards the inner cylinder according to a simple, particle-independent scaling law. After rescaling, the velocity profiles across the zones fall onto a universal master curve given by an error function. We study the shear zones also inside the material as function of both their local height and the total layer height.Comment: Minor corrections, accepted for PRL (4 pages, 6 figures

Anisotropic viscous models of large-deformation Mohr-Coulomb failure

We have developed a way to represent Mohr-Coulomb failure within a mantle-convection fluid dynamics code. We use a viscous model of deformation with an orthotropic viscoplasticity (a different viscosity is used for pure shear to that used for simple shear) to define a prefered plane for slip to occur given the local stress field. The simple-shear viscosity and the deformation can then be iterated to ensure that the yield criterion is always satisfied. We again assume the Boussinesq approximation, neglecting any effect of dilatancy on the stress field. An additional criterion is required to ensure that deformation occurs along the plane aligned with maximum shear strain-rate rather than the perpendicular plane, which is formally equivalent in any symmetric formulation. We also allow for strain-weakening of the material. The material can remember both the accumulated failure history and the direction of failure. We have included this capacity in a Lagrangian-integration-point finite element code and show a number of examples of extension and compression of a crustal block with a Mohr-Coulomb failure criterion. The formulation itself is general and applies to 2- and 3-dimensional problems