4/25/2023 0 Comments Define internal surfaces gmshWhen viscoelasticity is turned on, the Vp and Vs values that are read here are the UNRELAXED ones i.e. The tomographic model values are overimposed on this region, and defined in the file specified by the parameter TOMOGRAPHY_FILE. The values for density (rho) and Vp are ignored, however the value for Vs, i.e., A, must be either zero (0.0) to be recognized as an acoustic region or a positive non-zero value (e.g., 1.0) for an elastic region. Note that the model_number must be strictly positive, but the following domain number must be negative (-1) for tomographic models. For now, we only allow for a single tomography file and region. To impose a tomographic model on a given region, use (IV). To make a given region poroelastic, use (III). To make a given region anisotropic, use (II). Thus, to create acoustic (fluid) regions, just set the S wave speed to zero and the code will see that these elements are fluid and switch to the right equations there automatically, and automatically match them with the solid regions. To make a given region isotropic elastic, use (I) and make Vs be nonzero. To make a given region acoustic, use (I) and make Vs be zero. III: model_number 3 rhos rhof phi c kxx kxz kzz Ks Kf Kfr etaf mufr Qmu II: model_number 2 rho c11 c13 c15 c33 c35 c55 c12 c23 c25 0 QKappa Qmu The material types can be specified by one of the following line formats: I: model_number 1 rho Vp Vs 0 0 QKappa Qmu 0 0 0 0 0 0 With MODEL = default chosen, a variety of simple velocity and density models can be defined using the nbmodels section in the Par_file. In the solver the wave field is then described based on high-order Lagrange interpolants at Gauss-Lobatto-Legendre points, as is classical in spectral-element methods. Note that this convention is used to describe the geometry only. The local coordinate system being $\xi$ and $\eta$ ( xi and eta). Regarding mesh point numbering in the files created by the mesher, we use the classical convention of 4-node and 9-node finite elements ( NGNOD = 4 or NGNOD = 9, respectively): 4. The mesher will use the partitioner specified by parameter PARTITIONING_TYPE to load-balance the mesh for multiple processes. Otherwise, this has to be set to 1 for a serial run. If you have the code compiled with MPI support, you can specify the number of processes ($>1$) for the simulation to run on. They are available at SPECFEM3D user manual. If you need more details we do not have a detailed description of all the parameters for the 2D version in this manual but you can find useful information in the manuals of the 3D versions, since many parameters and the general philosophy is similar. The default DATA/Par_file provided in the root directory of the code contains detailed comments and should be almost self-explanatory (note that some of the older DATA/Par_file files provided in the EXAMPLES directory work fine but some of the comments they contain may be obsolete or even wrong thus refer to the default DATA/Par_file instead for reliable explanations). The executable `xspecfem2D` solves the seismic wave propagation. The executable `xmeshfem2D` creates the GLL mesh points and assigns specific model parameters. These files are required for running the solver in a subsequent step.įigure: Schematic workflow for a SPECFEM2D simulation. xmeshfem2D will output several files called Database?.bin, one for each process. To create the mesh, which will be stored in directory OUTPUT_FILES/. To run the mesher, please edit the main input file DATA/Par_file, describing the setup of your simulation. We provide two possibilities to do so: (1) relying on an external, hexahedral mesher, like Gmsh and CUBIT, or (2) using the provided, internal capabilities. The first step in running a spectral-element simulation consists of constructing a high-quality mesh for the region under consideration. Controlling how the mesh samples the wave field.Controlling the quality of an external mesh.Note about Cubit/Trelis built-in Python.How to use Cubit/Trelis to generate an external mesh.
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