# Receiver Function Forward simulation with Specfem3D_FWATR#

Attention

The Specfem3D_FWATR is under developing, so it has not been open accessed.

## Preparation#

For RF simulation, we invoked SEM-FK with plane wave injected to compute RFs, So parameter files are same as Specfem3D and SEM-FK, but an additional parameter file is required for RF calculation.

### Common configures#

• DATA/Par_file

• DATA/meshfem3D_files

• DATA/CMTSOLUTION

Note

The DATA/CMTSOLUTION must exist but its parameters will not work.

### Exclusive configures#

• src_rec/sources_setXX.dat: Map of source set XX and event id YY. The first field is read to define YY.

• src_rec/FKmodel_YY.dat

• src_rec/STATION_YY.dat

• fwat_params/FWAT.PAR: 4 parameters are required for RF calculation, Others are the same as FWAT.

• TSHIFT: Time shift before P

• NUM_FILTER: Number of Gaussian filters applied on RFs.

• F0: Array of Gaussian factors

• MAXIT: Maximum iterations

• MINDERR: Minimum residuals

### Meshes and Parameters#

Rules of meshes in Specfem3D has introduced how to create meshes and database, but there are still some key points need be highlighted.

• Coupling between FK and SEM domain: for high frequency simulation, the abrupt changes of adjacent materials result in wavefield scattering. Thus a taper zone is necessary between FK and SEM, which involved a smooth transition both in velocity and interface topography.

Note

• Taper zones are need to be set both along X and Y axis.

• The distance between first (last) station and the taper zone should be less than first Fresnel zone radius in effective depth.

• Coordinates of initial wavefront: if ORIGIN_WAVEFRONT is set, the initial wavefront should be out of the SEM domain. We can set up it to 4 bottom corner with different back-azimuth.

## Run simulation#

### Create database#

sed -i "/LOCAL_PATH                      =/c\LOCAL_PATH                      = ./OUTPUT_FILES/DATABASES_MPI" DATA/Par_file
sed -i "/LOCAL_PATH                      =/c\LOCAL_PATH                      = ./OUTPUT_FILES/DATABASES_MPI" DATA/meshfem3D_files/Mesh_Par_file

mpirun -np 4 ./bin/xmeshfem3D
mpirun -np 4 ./bin/xgenerate_databases


### Go forward simulation#

mpirun -np 4 ./bin/xfwat0_forward_data M00 setXX rf


RFs will be saved into data/YY with SAC format as knetwk.kstnm.kcmpnm.rf.sac