[CIG-SEISMO] need some advices to learn the SPECFEM2D codes

[Guoping Chen, Ph.D.]

Hi,
  I am studying the SPECFEM2D codes, and very intersting in the adjoint algorithm. But then I finish read the "Finite-frequency tomography using adjoint methods—
Methodology and examples using membrane surface waves" written by Carl Tape in 2007, and "Seismic tomography, adjoint methods, time reversal and banana-doughnut kernels" written by Jeroen Tromp in 2005, then tracing the SPECFEM2D codes, I am lost in the large program lines due to my poor Fortran skill and lack enough comments in the program codes. 
  Especially, I can not understand why the SPECFEM2D codes using like "rhop_ac_kl, rho_ac_kl" to define the phase-speed or density kernel, because them not dispear neither in Carl Tape paper published in 2007 nor in Jeroen Tromp paper published in 2005. That means in all your prior published papers, the kernel defined using K as the abbreviate for the kernel, why in program codes using "tho" as the pre-fix?
 
  To sum up, would your can give me some advices to how to learn the algorithm introduced in the published papers and learn the implement through the SPECFEM2D codes?

  Longer for your reply!



  

  
  sincerely your,
  ECE Duke, Guoping Chen
  14th, Dec., 2011