# FD3S

Finite-difference solver of the elastic wave equation in a spherical section. FD3S allows to model seismic wave attenuation as well as anisotropy with radial symmetry axis. The finite difference scheme is of fourth order in space and of second order in time. Arbitrarily complex Earth models can easily be included.

Authors: | Andreas Fichtner |
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General: | Wave propagation |

Code level: | Research |

Language: | Fortran 90/95 or later |

Associated groups: | Numerical Methods, Planetary Scale |

Supercomputing: | Distributed Memory (e.g., MPI) |

Grid dimensions: | 3D |

Coordinate system: | Spherical |

Method: | Finite differences |

Tested operating system: | Unix (e.g. SunOS, HP Unix) |

Rheology: | Viscoelastic anisotropic |

Boundary conditions: | Free surface (planar), Absorbing boundaries |

Grid type: | Rectangular, regular |

Solution type: | Numerical |

Total hits: | 7201 |

## Project Description

[A more detailed description is included in the package in the form of a pdf file.]

FD3S is a finite-difference solver of the elastic wave equation in a spherical section. It allows to model anisotropy with radial symmetry axis as well as seismic wave attenuation. The finite difference scheme is of fourth order in space and of second order in time.

A free-surface condition is implemented at the top of the computation domain. The unphysical boundaries are absorbing.

Arbitrarily complex distributions of density, elastic parameters (including those describing anisotropy) and anelastic parameters (relaxation times) can easily be included. Also, FD3S allows for non-homogeneous initial conditions.

Included in the FD3S package are programmes for the generation of material parameter distributions, initial value distributions and source time functions. Also, a small set of simple MATLAB tools - mostly for the plotting of the output - is available.

All source codes of FD3S are written in fortran90. The programme is fully parallelised but can very easily be run on a single machine by setting three simple parameters in the input files.

A detailed description of FD3S, including the setup of the mathematical problem, the discretisation and the implementations of anisotropy, attenuation and the free-surface, can be downloaded as pdf file.

The programme has been extensively tested on a single and on multiple processors. The results are accurate within the limitations of the finite-differencing technique. However, more quantitative testing is certainly still needed, and everybody is invited to participate.

FD3S was developped by Andreas Fichtner, Tarje Nissen-Meyer and Heiner Igel.