SPECFEM3D_GLOBE simulates global and regional (continental-scale) seismic wave propagation.
Effects due to lateral variations in compressional-wave speed, shear-wave speed, density, a 3D crustal model, ellipticity, topography and bathymetry, the oceans, rotation, and self-gravitation are all included.
The version 7.0 release offers GPU graphics card support for both OpenCL and CUDA hardware accelerators, based on an automatic source-to-source transformation library (Videau et al. 2013). It offers additional support for ADIOS file I/O formats and contains important bug fixes related to 3D topography and geographic/geocentric transformations. Seismogram file names adapt a new naming convention, with better compatibility to the seismogram specifications by the Incorporated Research Institutions for Seismology (IRIS).
The version embeds non-blocking MPI communications and includes several performance improvements in mesher and solver. It provides a perfectly load-balanced mesh for 3D mantle models honoring shallow oceanic Moho (depths less than 15 km) and deep continental Moho (depths greater than 35 km). It also accommodates European crustal models EPcrust (Molinari & Morelli, 2011) and EuCrust07 (Tesauro et al., 2008), which may be combined with global crustal model Crust2.0. Sedimentary wavespeeds are superimposed on the mesh if sediment thickness exceeds 2 km.
Additional new model routines are provided for the Comprehensive Earth Model (CEM) project, generic point-profile models (PPM) and Gauss-Lobatto-Legendre based models (GLL), with complementary tools for postprocessing adjoint sensitivity kernels and gradient-based model updates. The structure of the software has been simplified to facilitate easier implementation of new 3D models. The code accommodates general moment tensor files, and provides complete information in the SAC headers, as explained in detail in the updated user manual. New matrix-matrix multiplication routines, adapted from the book of Deville et al. (2002), and loop-vectorization help reduce the total number of memory accesses performed in each spectral element and improve code vectorization, thus enhance numerical performance of the version.
SPECFEM3D Cartesian simulates acoustic (fluid), elastic (solid), coupled acoustic/elastic, poroelastic or seismic wave propagation in any type of conforming mesh of hexahedra (structured or not.) It can, for instance, model seismic waves propagating in sedimentary basins or any other regional geological model following earthquakes. It can also be used for non-destructive testing or for ocean acoustics.
SPECFEM3D_Cartesian version 2.0 uses the continuous Galerkin spectral-element method, which can be seen as a particular case of the discontinuous Galerkin technique with optimized efficiency owing to its tensorized basis functions, to simulate forward and adjoint coupled acoustic-(an)elastic seismic wave propagation on arbitrary unstructured hexahedral meshes.
This major new release benefits from advances in hexahedral meshing, load balancing and code optimizations. Meshing may be accomplished using a mesh generation tool kit such as CUBIT, GiD or Gmsh, and load balancing is facilitated by graph partitioning based on the SCOTCH library, which is included in the package. The previous internal layer cake mesher has been extended to allow greater flexibility and also continues to be available. Topography, bathymetry and Moho undulations are readily included in a mesh, and physical dispersion and attenuation associated with anelasticity are accounted for using a series of standard linear solids. Coupling between fluid and solid regions is accommodated using domain decomposition, thereby facilitating off-shore simulations. Finite-frequency Fréchet derivatives for earthquake and seismic interferometric data are calculated based on adjoint methods in both fluid and solid domains, thereby facilitating "adjoint tomography" with earthquakes and seismic noise.
SPECFEM2D simulates forward and adjoint seismic wave propagation in two-dimensional acoustic, (an)elastic, poroelastic or coupled acoustic-(an)elastic-poroelastic media, with Convolution PML absorbing conditions.
Meshing is based for instance upon Gmsh, Cubit, GiD or a simple internal mesher provided with the package, and the acoustic/(an)elastic/poroelastic solvers are based upon the spectral-element method. The package may also be used to calculate finite-frequency kernels and has full adjoint capabilities. Convolution PML absorbing conditions are used to efficiently absorb the outgoing wave field on the outer edges of the grid.