# EDGE-V¶

EDGE Velocity (EDGE-V) is a tool used to perform velocity-aware mesh refinement and annotate meshes with background data of velocity models. It is developed based on the SCEC Unified Community Velocity Model (UCVM), which is used as interface to different velocity models.

## Dependencies¶

EDGE-V has the following dependencies:

## Build Instructions¶

### UCVMC¶

Install UCVM’s C-interface by following the commands below:

git clone https://github.com/SCECcode/UCVMC.git
git checkout v17.1.0
cd UCVMC/largefiles
./get_large_files.py
./check_largefiles_md5.py
./stage_large_files.py
cd ..
./ucvm_setup.py


On Cray systems, in particular Cori Phase II, use:

CRAYPE_LINK_TYPE=dynamic CXX=g++ CC=gcc F77=gfortran F90=gfortran FC=gfortran ./ucvm_setup.py


During the installation process in ./ucvm_setup.py, it is recommended to install all the libraries and models to get the full support. Be aware that it will occupy a large amount of storage. Please refer to the UCVMC documentation for detailed instructions.

### MOAB¶

Details on the MOAB installation are given in Sec. Installation.

### EDGE-V¶

Analogue to EDGE, EDGE-V uses SCons for the installation. With a MOAB installation in ../../libs and UCVM installation in ../../libs/ucvm-17.1.0/, the build commands reads as:

scons moab=../../libs ucvm=../../libs/ucvm-17.1.0/ zlib=../../libs hdf5=../../libs netcdf=no


## Usage¶

### Overview¶

EDGE-V accepts a single command line argument, which is the configuration file (here: edge_v.conf):

./edge_v -f edge_v.conf


An exemplary configuration is given below:

# ucvm parameters
ucvm_config=../../libs/ucvm-17.1.0/
ucvm_model_list=cvmsi
ucvm_cmode=UCVM_COORD_GEO_DEPTH
ucvm_type=cmb

# projections
proj_mesh=+proj=tmerc +units=m +axis=enu +no_defs +datum=WGS84 +k=0.9996 +lon_0=-117.916 +lat_0=33.933
proj_vel=+proj=latlong +datum=WGS84

# trafo when scaling from mapped domain to mesh
trafo_x=1.0 0.0 0.0
trafo_y=0.0 1.0 0.0
trafo_z=0.0 0.0 -1.0

refinement_center_xy=0.0 0.0
refinement_relative_cls=0.2 0.8

# velocity rule
vel_rule=highf2018

# input mesh file
mesh_file=gen/la_habra_small_refined.msh

# output files
pos_file=gen/la_habra_small.pos
anno_file=gen/la_habra_small_refined_vmtags.h5m


In detail, the respective parameters are given as:

Parameter Description
ucvm_config UCVM’s configuration file, which is automatically generated in the installation process. This is analogue to the -f option of the ucvm_query tool (see ucvm_query --help for details).
ucvm_model_list The used sub-models, which are queried for the velocity data. This is analogue to the -m option of ucvm_query.
ucvm_cmode Used coordinate mode, when querying UCVM. Valid options are UCVM_COORD_GEO_DEPTH and UCVM_COORD_GEO_ELEV.
ucvm_type Values used from the UCVM query, either gtl, crust or cmb (combination of gtl and crust).
proj_mesh Projection, used for deriving the Cartesian coordinates of the mesh.
proj_vel Projection, used for querying UCVM
trafo_x, trafo_y, trafo_z (Optional) Transformation, applied to the mesh nodes, before querying the UCVM. The three-valued vectors are space-separated. For example, if trafo_x=0.5 0.0 0.5, the x-coordinate of every node in the query, would be 0.5*x + 0.5*z.
refinement_center_xy Center in x- and y-direction of the cylinders, used for the generated Gmsh view.
refinement_radii_xy Radii of the inner and outer circle, used for the generated Gmsh view. Vertices in the inner cylinder are assigned the first characteristic length. Vertices outside the outer cylinder are assigned the second characteristic length. Vertices in the transition zone coarsen linearly between the provided characteristic lengths.
refinement_relative_cls Relative characteristic lengths of the vertices in the Gmsh view. The characteristic lengths are based on the s-wave velocities $$v_s$$ at 1Hz. For example, if a vertex in the inner cylinder has a relative length of $$\text{cl}_\text{i}$$, we set: $$\text{cl}_v = \text{cl}_\text{i} * v_s$$ for the vertex’s characteristic length.
mesh_file Path to the mesh file, which is read. Format can be everything, which MOAB supports
pos_file Path to the Gmsh view, which is written.
anno_file Path to the velocity annotated mesh file, which is written. Format can be everything, which MOAB supports.

## Vs-based Mesh Refinement¶

EDGE-V’s script mesh_refinement.sh performs an iterative mesh refinement to generate a final mesh, that adapts to the velocity model’s s-wave velocities. The script uses the given Gmsh-geo file to produce an initial (coarse) mesh. This coarse mesh is used as input for edge_v. Next, the script generates a Gmsh-view, which contains the targeted characteristic lengths at the vertices. This Gmsh-view is used to generate a new mesh and the procedure iterates by annotating the newly generated mesh.

Command line arguments for mesh_refinement.sh are:

Argument Description
-m Model name (required)
-c Config directory (required)
-o Mesh directory (required)
-p Handling intermediate mesh files (optional). 1: Generate and zip intermediate files (done by default), 2: Generate but don’t zip intermediate files, 3: Do not generate intermediate files (i.e. only generate refined mesh)
-n Number of iterations (optional, by default 10)
-r Remote meshing (optional, by default 0)
-u Remote username (optional)
-d Remote domain name (optional)
-g Remote location of Gmsh executable (optional)
-t Remote mesh directory (optional)

At the end of the iterations, a final refined mesh file (*_refined.msh) is generated.