Example 00: Checkerboard test for Isotropic Ambient noise Surface Wave Tomography

This example reproduces the SurfATTPP/examples/00_checkerboard_iso workflow. It builds a synthetic isotropic checkerboard model, forward-calculates surface-wave travel times, and then inverts the synthetic data to test how well the checker pattern can be recovered.

What is included

The example directory contains these files:

input_params.yml: inversion settings for the checkerboard test
src_rec_file_ph.csv: phase-velocity travel-time table
src_rec_file_gr.csv: group-velocity travel-time table
run_this_example.sh: helper script that runs the full workflow
plot_model.ipynb: notebook for plotting the recovered model

Parameter setup

The default input_params.yml is configured for a small isotropic test case:

Rayleigh waves (iwave: 2)
both phase and group data enabled with equal weights
model depth range of 0-15 km
grid interval of 0.02/0.02/0.5
linear initial model with vel_range: [1.8, 4.2]
40 inversion iterations with LBFGS optimization method

Topography is disabled in this example.

Run the example

From the example directory, run:


mkdir -p OUTPUT_FILES
cp src_rec_file_ph.csv OUTPUT_FILES/src_rec_file_forward_PH.csv
cp src_rec_file_gr.csv OUTPUT_FILES/src_rec_file_forward_GR.csv
 
mpirun -np 8 surfatt_cb_fwd -i input_params.yml -n 2/3/2 -m 0.2 -p 0.08
mpirun -np 8 surfatt_tomo -i input_params.yml

This is the same workflow used in run_this_example.sh.

What the workflow does

Copies the phase travel-time table into OUTPUT_FILES as the reference data file.
Uses surfatt_cb_fwd to generate a 2 x 3 x 2 checkerboard model and synthetic travel times.
Runs surfatt_tomo to invert the synthetic data and recover the isotropic velocity perturbations.

Expected outputs

After the run finishes, inspect the OUTPUT_FILES directory for:

final_model.h5: recovered isotropic S-wave velocity model
model_iter.h5: intermediate models written during inversion
objective_function.txt: misfit history for each iteration
src_rec_file_forward_*.csv: forward-calculated travel-time data

Visualization

Open plot_model.ipynb in the example directory to compare the initial and recovered models. The notebook reads OUTPUT_FILES/model_iter.h5 and OUTPUT_FILES/final_model.h5, computes velocity perturbations, and plots map views of the checkerboard recovery.