[cig-commits] [commit] devel, master: added explanations from Jeroen about the steps to follow when using PARTIAL_PHYS_DISPERSION_ONLY instead of UNDO_ATTENUATION (c6e8e9a)

[cig_noreply at geodynamics.org]

Repository : https://github.com/geodynamics/specfem3d_globe

On branches: devel,master
Link       : https://github.com/geodynamics/specfem3d_globe/compare/bc58e579b3b0838a0968725a076f5904845437ca...be63f20cbb6f462104e949894dbe205d2398cd7f

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commit c6e8e9a46f1a4bfcf8b3725426d1dd528b7dabea
Author: Dimitri Komatitsch <komatitsch at lma.cnrs-mrs.fr>
Date:   Wed Sep 17 15:23:15 2014 +0200

    added explanations from Jeroen about the steps to follow when using PARTIAL_PHYS_DISPERSION_ONLY instead of UNDO_ATTENUATION


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c6e8e9a46f1a4bfcf8b3725426d1dd528b7dabea
 doc/USER_MANUAL/manual_SPECFEM3D_GLOBE.tex | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/doc/USER_MANUAL/manual_SPECFEM3D_GLOBE.tex b/doc/USER_MANUAL/manual_SPECFEM3D_GLOBE.tex
index 0a07931..0057de3 100644
--- a/doc/USER_MANUAL/manual_SPECFEM3D_GLOBE.tex
+++ b/doc/USER_MANUAL/manual_SPECFEM3D_GLOBE.tex
@@ -494,7 +494,7 @@ Note about the OpenCL version: the OpenCL calculation kernels were
 created by Brice Videau and Kevin Pouget from Grenoble, France, using
 their software package called BOAST; see:
 
-Title:	BOAST: Bringing Optimization through Automatic Source-to-Source Tranformations,
+Title:  BOAST: Bringing Optimization through Automatic Source-to-Source Tranformations,
 2013,
 Videau, B, Marangozova-Martin, V, Cronsioe, J,
 Tokyo, Japan,
@@ -712,7 +712,8 @@ than~$90^{\circ}$, thereby accommodating smaller-scale simulations. }
 
 
 To run the mesher for a global simulation, the following parameters
-need to be set in the \texttt{Par\_file}:
+need to be set in the \texttt{Par\_file} (the list below might be slightly obsolete or incomplete; for an up-to-date
+version, see comments in the default \texttt{Par\_file} located in directory \texttt{DATA}:
 
 \begin{description}
 \item [{\texttt{SIMULATION\_TYPE}}] is set to 1 for forward simulations,
@@ -901,6 +902,17 @@ length of the numerical simulation, i.e., twice the record length
 requires twice as much CPU time. This feature is not used at the time
 of meshing but is required for the solver, i.e., you may change this
 parameter after running the mesher.
+\item [{\texttt{PARTIAL\_PHYS\_DISPERSION\_ONLY or UNDO\_ATTENUATION}}] To undo attenuation for sensitivity kernel calculations or forward runs with \texttt{SAVE\_FORWARD}
+use one (and only one) of the two flags below. \texttt{UNDO\_ATTENUATION} is much better (it is exact)
+but requires a significant amount of disk space for temporary storage.
+When using \texttt{PARTIAL\_PHYS\_DISPERSION\_ONLY}, to make the approximation reasonably OK you need to take the following steps:
+%
+1/ To calculate synthetic seismograms, do a forward simulation with full attenuation for the model of interest. The goal is to get synthetics that match the data as closely as possible.\\
+2/ Make measurements and produce adjoint sources by comparing the resulting synthetics with the data. In the simplest case of a cross-correlation traveltime measurement, use the time-reversed synthetic in the window of interest as the adjoint source.\\
+2/ Do a second forward calculation with \texttt{PARTIAL\_PHYS\_DISPERSION\_ONLY = .true.} and save the last snapshot.\\
+3/ Do an adjoint calculation using the adjoint source calculated in 1/, the forward wavefield reconstructed based on 2/, use \texttt{PARTIAL\_PHYS\_DISPERSION\_ONLY = .true.} for the adjoint wavefield, and save the kernel.\\
+Thus the kernel calculation uses \texttt{PARTIAL\_PHYS\_DISPERSION\_ONLY = .true.} for both the forward and the adjoint wavefields. This is in the spirit of the banana-donut kernels. But the data that are assimilated are based on the full 3D synthetic with attenuation.
+%
 \item [{\texttt{MOVIE\_SURFACE}}] Set to \texttt{.false.}, unless you want
 to create a movie of seismic wave propagation on the Earth's surface.
 Turning this option on generates large output files. See Section \ref{sec:Movies}
@@ -3799,7 +3811,7 @@ Accordingly, when you run a simulation the band code will be chosen depending on
 {\footnotesize       vsv=vsv*(1.0d0+dvs) }{\footnotesize \par}
 {\footnotesize       vsh=vsh*(1.0d0+dvs) }{\footnotesize \par}
 {\footnotesize       rho=rho*(1.0d0+drho) }{\footnotesize \par}
-{\footnotesize	... }{\footnotesize \par}
+{\footnotesize  ... }{\footnotesize \par}
   \end{lyxcode}
  You could modify this to add different perturbations for vph and vpv, resp. vsh and vsv.
  This would basically mean that you add transverse isotropic perturbations.