CIG-LLNL Computational Seismology Workshop

Table of Contents

1. Overview
2. Introduction
3. Part I: Setting up SPECFEM3D_GLOBE
4. Part II: Continental-scale Simulations
5. Part III: Visualization
6. Part IV: Adjoint Simulations (Bonus)
   1. Run Forward Simulation and Save State Variables
   2. Prepare the Adjoint Source(s)
   3. Run Kernel Simulation
7. Further Work
8. Resources

Part IV: Adjoint Simulations (Bonus)

In this final part of the tutorial, we will look at how to run adjoint simulations. SPECFEM3D_GLOBE supports two types of adjoint simulations: for source inversions and for finite-frequency kernels. In this tutorial, we will focus on the application to finite-frequency kernels, but the steps required are similar for both applications. The steps we need to take are the following:

• Run Forward Simulation and Save State Variables
• Prepare the Adjoint Source(s)
• Run Kernel Simulation

Run Kernel Simulation

Once we have run the forward simulation and generated the adjoint sources, running the kernel simulation is straight forward. In the Par_file we need to change two parameters. First, we don’t want to save the state variables, so we set the SAVE_FORWARD parameter to .false. again.

  SAVE_FORWARD                    = .false.   # save last frame of forward simulation or not

Secondly, we need to change the simulation type. We want to run a kernel simulation, and therefore we need to set the SIMULATION_TYPE parameter accordingly

  SIMULATION_TYPE                 = 3   # set to 1 for forward simulations, 2 for adjoint simulations for sources, and 3 for kernel simulations

Once we have made these modifications to the Par_file, we can submit the submit_solver script to the job queue with the following command

      sbatch submit_solver

and monitor the progress with the squeue command. Once the simulation ends, we check the OUTPUT_FILES/output_solver.txt file to make sure that the solver ran successfully.

For details on how to visualize the output from the kernel simulations, and instructions on how to run adjoint simulations for sources, please consult the SPECFEM3D_GLOBE manual.

In this section, we have looked at how to run a kernel simulation using SPECFEM3D_GLOBE, and this concludes the tutorial.

The next section contains a list of suggestions of further work that you can try if you have completed the tutorial up until this point.

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