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The Geodynamic World Builder (GWB) is an open source code library intended to set up initial conditions for computational geodynamic models and/or visualize complex 3d teconic setting, in both Cartesian and Spherical geometries. The inputs for the JSON-style parameter file are not mathematical, but rather a structured nested list describing tectonic features, e.g. a continental, an oceanic or a subducting plate. Each of these tectonic features can be assigned a specific temperature profile (e.g. plate model) or composition label (e.g. uniform). For each point in space, the GWB can return the composition and/or temperature. It is written in C++, but can be used in almost any language through its C, Python and Fortran wrappers. Various examples of 2D and 3D subduction settings are presented. 

Olivine lattice preferred orientation (LPO), or texture, forms in relation to deformation mechanisms such as dislocation creep and can be observed in the upper mantle as seismic anisotropy. Olivine is also mechanically anisotropic, meaning that it responds to stresses differently depending on the direction of the stress. Understanding the interplay between anisotropic viscosity (AV) and LPO, and their role in deformation, is necessary for relating seismic anisotropy to mantle flow patterns. In this study, we employ three methods to predict olivine texture (D-Rex, MDM, and MDM+AV) in a shear box model and a subduction model. D-Rex and MDM are two representative texture development methods that have been compared before, and our results are in line with previous studies showing that textures computed by D-Rex develop faster and are stronger and more point-like than textures calculated with MDM. MDM+AV uses the same isotropic mantle stresses and particle paths as D-Rex and MDM but includes the effect of AV for texture predictions. MDM+AV predicts a texture similar to MDM with a distinct girdle-like orientation for simple shear deformation or at low strain in the subduction model. At larger strains, MDM+AV’s textures are more point-like and stronger compared to the other two methods. The effective viscosity for MDM+AV drops by up to 60% in a shear box model and can be either strengthened or weakened relative to isotropic viscosity for different regions of the subduction model experiencing different patterns of deformation. Our results emphasize the significant role of AV in olivine texture development, which could substantially affect geodynamic processes in the upper mantle. 

We are pleased to announce the release of ASPECT 2.5.0. ASPECT is the Advanced Solver for Problems in Earth's ConvecTion. It uses modern numerical methods such as adaptive mesh refinement, multigrid solvers, and a modular software design to provide a fast, flexible, and extensible mantle convection solver. ASPECT is available from https://aspect.geodynamics.org/ and the release is available from https://geodynamics.org/resources/aspect and https://github.com/geodynamics/aspect/releases/tag/v2.5.0 Among others this release includes the following significant changes: ASPECT now includes version 0.5.0 of the Geodynamic World Builder. (Menno Fraters and other contributors) ASPECT's manual has been converted from LaTeX to Markdown to be hosted as a website at https://aspect-documentation.readthedocs.io. (Chris Mills, Mack Gregory, Timo Heister, Wolfgang Bangerth, Rene Gassmoeller, and many others) New: ASPECT now requires deal.II 9.4 or newer. (Rene Gassmoeller, Timo Heister) ASPECT now supports a DebugRelease build type that creates a debug build and a release build of ASPECT at the same time. It can be enabled by setting the CMake option CMAKE_BUILD_TYPE to DebugRelease or by typing "make debugrelease". (Timo Heister) ASPECT now has a CMake option ASPECT_INSTALL_EXAMPLES that allows building and install all cookbooks and benchmarks. ASPECT now additionally installs the data/ directory. Both changes are helpful for installations that are used for teaching and tutorials. (Rene Gassmoeller) Changed: ASPECT now releases the memory used for storing initial conditions and the Geodynamic World Builder after model initialization unless an owning pointer to these objects is kept. This reduces the memory footprint for models initialized from large data files. (Wolfgang Bangerth) Added: Various helper functions to distinguish phase transitions for different compositions and compositional fields of different types. (Bob Myhill) Added: The 'adiabatic' initial temperature plugin can now use a spatially variable top boundary layer thickness read from a data file or specified as a function in the input file. Additionally, the boundary layer temperature can now also be computed following the plate cooling model instead of the half-space cooling model. (Daniel Douglas, John Naliboff, Juliane Dannberg, Rene Gassmoeller) New: ASPECT now supports tangential velocity boundary conditions with GMG for more geometries, such as 2D and 3D chunks. (Timo Heister, Haoyuan Li, Jiaqi Zhang) New: Phase transitions can now be deactivated outside a given temperature range specified by upper and lower temperature limits for each phase transition. This allows implementing complex phase diagrams with transitions that intersect in pressure-temperature space. (Haoyuan Li) New: There is now a postprocessor that outputs the total volume of the computational domain. This can be helpful for models using mesh deformation. (Anne Glerum) New: Added a particle property 'grain size' that tracks grain size evolution on particles using the 'grain size' material model. (Juliane Dannberg, Rene Gassmoeller) Fixed: Many bugs, see link below for a complete list. (Many authors. Thank you!). A complete list of all changes and their authors can be found at https://aspect.geodynamics.org/doc/doxygen/changes_between_2_84_80_and_2_85_80.html Wolfgang Bangerth, Juliane Dannberg, Menno Fraters, Rene Gassmoeller, Anne Glerum, Timo Heister, Bob Myhill, John Naliboff, and many other contributors. 

Abstract Mantle convection models based on geophysical constraints have provided us with a basic understanding of the forces driving and resisting plate motions on Earth. However, existing studies computing the balance of underlying forces are contradicting, and the impact of plate boundary geometry on surface deformation remains unknown. We address these issues by developing global instantaneous 3‐D mantle convection models with a heterogeneous density and viscosity distribution and weak plate boundaries prescribed using different geometries. We find that the plate boundary geometry of the Global Earthquake Model (GEM, Pagani et al., 2018,https://doi.org/10.1177/8755293020931866), featuring open plate boundaries with discrete lithospheric‐depth weak zones in the oceans and distributed crustal faults within continents, achieves the best fit to the observed GPS data with a directional correlation of 95.1% and a global point‐wise velocity residual of 1.87 cm/year. A good fit also requires plate boundaries being 3 to 4 orders of magnitude weaker than the surrounding lithosphere and low asthenospheric viscosities between 5 × 10¹⁷and 5 × 10¹⁸ Pa s. Models without asthenospheric and lower mantle heterogeneities retain on average 30% and 70% of the plate speeds, respectively. Our results show that Earth's plate boundaries are not uniform and better described by more discrete plate boundaries within the oceans and distributed faults within continents. Furthermore, they emphasize the impact of plate boundary geometry on the direction and speed of plate motions and reaffirm the importance of slab pull in the uppermost mantle as a major plate driving force.