[cig-commits] r17055 - in seismo/3D: SPECFEM3D/trunk SPECFEM3D_GLOBE/trunk

[dkomati1 at geodynamics.org]

Author: dkomati1
Date: 2010-07-23 07:32:22 -0700 (Fri, 23 Jul 2010)
New Revision: 17055

Modified:
   seismo/3D/SPECFEM3D/trunk/todo_list_please_dont_remove.txt
   seismo/3D/SPECFEM3D_GLOBE/trunk/todo_list_please_dont_remove.txt
Log:
updated the todo list


Modified: seismo/3D/SPECFEM3D/trunk/todo_list_please_dont_remove.txt
===================================================================
--- seismo/3D/SPECFEM3D/trunk/todo_list_please_dont_remove.txt	2010-07-20 16:52:22 UTC (rev 17054)
+++ seismo/3D/SPECFEM3D/trunk/todo_list_please_dont_remove.txt	2010-07-23 14:32:22 UTC (rev 17055)
@@ -1,7 +1,68 @@
 
-To-do list for SPECFEM3D_SESAME, by Dimitri Komatitsch
-------------------------------------------------------
+To-do list for SPECFEM3D, by Dimitri Komatitsch
+-----------------------------------------------
 
+Date: Fri, 23 Jul 2010 01:30:16 +0200
+From: Dimitri Komatitsch <dimitri.komatitsch at univ-pau.fr>
+To: Anne Sieminski <anne.sieminski at obs.ujf-grenoble.fr>
+CC: Jeroen Tromp <jtromp at princeton.edu>, Min Chen <mchen at gps.caltech.edu>, Vala Hjorleifsdottir <vala at ldeo.columbia.edu>, Brian Savage <savage at uri.edu>, Shiann-Jong Lee <sjlee at earth.sinica.edu.tw>, Dimitri Komatitsch <dimitri.komatitsch at univ-pau.fr>, Roland Martin <roland.martin at univ-pau.fr>, Bernhard Schuberth <mail at bernhard-schuberth.de>, Carl Tape <carltape at fas.harvard.edu>, Anne Sieminski <anne.sieminski at obs.ujf-grenoble.fr>, Paul Friberg <p.friberg at isti.com>, Kasper van Wijk <kasper at cgiss.boisestate.edu>, Dylan Mikesell <dmikesell at cgiss.boisestate.edu>, Federica Magnoni <federica.magnoni at ingv.it>, Ebru Bozdag <bozdag at princeton.edu>, Hejun Zhu <hejunzhu at princeton.edu>, Pieyre Le Loher <pieyre.le_loher at inria.fr>, Christina Morency <cmorency at Princeton.EDU>, Emanuele Casarotti <emanuele.casarotti at gmail.com>, Piero Basini <basini at bo.ingv.it>, Emmanuel Chaljub <Emmanuel.Chaljub at obs.ujf-grenoble.fr>, Tarje Nissen-Meyer <tarje at princeton.edu>, Qinya Liu <liuqy at physics.utoronto.ca>, Yang Luo <yangl at Princeton.EDU>, Daniel Peter <dpeter at Princeton.EDU>, Ying Zhou <yingz at vt.edu>
+Subject: Re: milieux acoustiques
+
+Dear Anne,
+
+I answer in English and cc all the other developers because other people 
+may be interested. Yes, SPECFEM3D version 2 (which is a beta
+version right now) can handle acoustic media in addition to 
+(visco)elastic layers. Daniel Peter has added support for that
+(based in part on our implementation in the 2D version SPECFEM2D-6.0.0
+I guess, or on what was already implemented in SPECFEM3D_GLOBE, i.e.,
+the fluid outer core of the Earth).
+
+However, there is a hidden problem if you want to use acoustic layers 
+for oil industry simulations: our acoustic formulation in the 3D code
+(at least in SPECFEM3D_GLOBE for sure) can only handle one acoustic 
+layer with a smooth velocity gradient (which is the case in the outer 
+core) but not a first-order acoustic-acoustic discontinuity, which from 
+a physical point of view does not make much sense. *BUT* this implies
+that if you take an elastic oil industry model and make it acoustic 
+(with layers) by only considering Vp, as people often do in oil 
+companies, the code will fail (more precisely, and unfortunately, it 
+will not crash but will produce seismograms that will not be correct).
+
+This is because for acoustic-acoustic interfaces one should use a 
+potential of (density * displacement) rather than a potential of 
+displacement only in order to enforce continuity of pressure 
+automatically in the weak formulation of the problem.
+
+In the 2D code that's what I do (which means you can safely use
+the 2D code for acoustic oil industry models). But I think that
+this is not done in the 3D code because I assume Daniel took the 
+acoustic code from SPECFEM3D_GLOBE, in which case a potential
+of displacement is used and acoustic-acoustic interfaces are not handled 
+properly.
+
+I guess one day we should switch to a potential of (density * 
+displacement) in the 3D code, as I did in the 2D code two years ago.
+Otherwise I think one day some users will use it for oil industry models
+and will get erroneous seismograms. That's (very) easy to do but 
+unfortunately I do not have time for now...
+
+Hope this helps,
+Cheers,
+
+Dimitri.
+
+On 06/23/2010 05:42 PM, Anne Sieminski wrote:
+> Bonjour Dimitri,
+>
+> Je vois que SPECFEM2D-6.0.0 (disponible sur le site de CIG) permet de
+> faire des calculs dans des modèles acoustiques. La même option est-elle
+> en projet pour SPECFEM3D (ancien SPECFEM3D_BASIN) ? J'ai un peu perdu le
+> fil de toutes les nouveautés... Désolée !
+>
+> Merci,
+> Anne
+
 - serial domain decomposition is already a limitation in the case of regional seismology, because serial meshes can be very large. One option would be to switch to ParMetis or PT-Scotch, i.e., the parallel version of these domain decomposition packages. I know that PT-Scotch works great and is pretty fast. Another option is ZOLTAN from Sandia National Labs, but I do not know if it is serial or parallel.
 
 - update the manual before the first official release of version 2.0
@@ -37,11 +98,11 @@
 
 - we could add support for Discontinuous Galerkin, and/or for SEM on tetrahedra and pyramids
 
-- Regarding memory size (getting an estimate of memory consumption in SESAME),
+- Regarding memory size (getting an estimate of memory consumption in SPECFEM3D),
 somebody should just cut and paste my SPECFEM3D_GLOBE routine
 "SPECFEM3D_GLOBE/version41_beta/src/memory_eval.f90", which
 I call from "SPECFEM3D_GLOBE/version41_beta/src/create_header_file.f90".
-It would work for SESAME as well (with minor modifications).
+It would work for SPECFEM3D as well (with minor modifications).
 
 - add SOURCESOLUTION in addition to CMTSOLUTION, to choose between a CMT source and a force source
 
@@ -138,7 +199,7 @@
 of description of the figures?).
 SCOTCH (serial) and PT-SCOTCH (parallel) is then better.
 (faster, uses less memory etc.)
-Because of that, we have removed support for METIS in SESAME.
+Because of that, we have removed support for METIS in SPECFEM3D.
 It can still be called indirectly from SCOTCH (there is an option
 in SCOTCH to call METIS instead). But this is a bad idea because
 the partition obtained is worse.

Modified: seismo/3D/SPECFEM3D_GLOBE/trunk/todo_list_please_dont_remove.txt
===================================================================
--- seismo/3D/SPECFEM3D_GLOBE/trunk/todo_list_please_dont_remove.txt	2010-07-20 16:52:22 UTC (rev 17054)
+++ seismo/3D/SPECFEM3D_GLOBE/trunk/todo_list_please_dont_remove.txt	2010-07-23 14:32:22 UTC (rev 17055)
@@ -4,6 +4,53 @@
 
 Things that could be done in a future version:
 
+Subject: Re: SEM attenuation
+Date: Fri, 23 Jul 2010 12:16:40 +0200
+From: Tarje Nissen-Meyer <tarjen at ethz.ch>
+Organization: ETH Zurich
+To: Dimitri Komatitsch <dimitri.komatitsch at univ-pau.fr>
+CC: <yingz at vt.edu>, Jeroen Tromp <jtromp at princeton.edu>, Min Chen	<mchen at gps.caltech.edu>, Vala Hjorleifsdottir <vala at ldeo.columbia.edu>,	"Brian Savage" <savage at uri.edu>, Shiann-Jong Lee <sjlee at earth.sinica.edu.tw>,	"Roland Martin" <roland.martin at univ-pau.fr>, Bernhard Schuberth	<mail at bernhard-schuberth.de>, Carl Tape <carltape at fas.harvard.edu>, "Anne Sieminski" <anne.sieminski at obs.ujf-grenoble.fr>, Paul Friberg	<p.friberg at isti.com>, Kasper van Wijk <kasper at cgiss.boisestate.edu>, "Dylan Mikesell" <dmikesell at cgiss.boisestate.edu>, Federica Magnoni	<federica.magnoni at ingv.it>, Ebru Bozdag <bozdag at princeton.edu>, Hejun Zhu	<hejunzhu at princeton.edu>, Pieyre Le Loher <pieyre.le_loher at inria.fr>,	Christina Morency <cmorency at Princeton.EDU>, Emanuele Casarotti	<emanuele.casarotti at gmail.com>, Piero Basini <basini at bo.ingv.it>, "Emmanuel Chaljub" <Emmanuel.Chaljub at obs.ujf-grenoble.fr>, Qinya Liu	<liuqy at physics.utoronto.ca>, Yang Luo <yangl at Princeton.EDU>, Daniel Peter	<dpeter at Princeton.EDU>
+
+Hi all,
+
+Just to add that symplectic schemes are based on conservative systems
+(they approximate the Hamiltonian) and we don't know yet how they behave
+for dissipative media. But still of course something to be added and
+looked at. Should also give credit to Jean-Paul Ampuero who really first
+suggested trying these schemes for elastodynamics with the SEM.
+
+Best regards,
+Tarje
+
+On 23/07/10 02:21, Dimitri Komatitsch wrote:
+>
+> Hi Ying,
+>
+> Thank you for your message. I cc all the other developers in order to
+> know if anybody else has seen a similar problem with attenuation.
+> That is weird because in the SPECFEM3D manual Anne Sieminski added
+> nice pictures showing an excellent fit with normal modes down to 9
+> seconds (if I remember correctly), including attenuation in at least some of
+> the tests (Anne, could you maybe confirm that?).
+>
+> What I know for sure if that back in 1999 when I developed the time
+> scheme for attenuation I used a trick that made implementation much
+> easier but that also makes the 4th order Runge Kutta (RK4) time scheme
+> become second order only, i.e. RK2 instead of RK4. This means that for
+> very long simulations (for instance multi-orbit surface waves)
+> attenuation can become inaccurate because of a lack of accuracy in the
+> time scheme (in which case reducing Delta_t purposely solves the
+> problem, but of course makes the simulation more expensive).
+>
+> A nice way of solving this problem would be to switch to better time
+> schemes such as the symplectic time scheme that Tarje introduced in a
+> GJI paper a few years ago. Tarje and I should probably implement that
+> in the code one day... (therefore I cc him; we talked about this at
+> the EGU meeting in May)
+>
+> Thank you,
+> Dimitri.
+
 - symplectic time scheme (will be done by Tarje Nissen-Meyer and/or Jean-Paul Ampuero) (would be useful in the 2D version of the code as well):
 Hi Jeroen, Perfect. I think talking to Jean-Paul Ampuero would be useful
 as well because in Utrecht last year he had told us that