[CIG-SEISMO] Help needed to use deformation field as an input of SPECFEM2D

[Dimitri Komatitsch]

Hi again Jérôme,

You can also maybe have a look at the "pre-stress" section of e.g. the 
book of Dahlen and Tromp (1998) 
https://press.princeton.edu/titles/6361.html ; let me cc Jeroen, he will 
know much more about this than I do ;-)

Best,
Dimitri.

On 05/24/2018 03:22 PM, Dimitri Komatitsch wrote:
> 
> Hi Jérôme,
> 
> Thanks for your question. Since the equation is second order in time, 
> one needs two initial conditions, usually we input the displacement 
> vector and the velocity vector at time t = 0 when the medium is not 
> initially at rest; another option (mathematically equivalent in the 
> context of the discretized equation) is to input the displacement vector 
> at two different times, say t = 0 and t = + delta_t for instance, where 
> delta_t is the time step of the time scheme.
> 
> I am not familiar with how this can (or cannot) be done easily by 
> inputing spatial gradients of that (for instance the strain), but the 
> answer is very likely for instance in Tom Hughes' 1987 book 
> https://www.amazon.com/Finite-Element-Method-Mechanical-Engineering/dp/0486411818 
> 
> (around chapter 9 or so if I remember correctly).
> 
> Best wishes,
> Dimitri.
> 
> On 05/24/2018 12:24 PM, AZZOLA Jerome (JDS) wrote:
>> Hello,
>>
>> First, I would like to thank CIG Seismology for providing Specfem2D 
>> and other very useful Software with free access.
>> I'm a PhD student at IPGS - University of Strasbourg and I use 
>> Specfem2D to simulate the propagation of waves in a plate containing 
>> holes and meshed using the external mesher GMSH. The mesh input in 
>> Specfem2D is continuously deformed using Code_Aster, a finite element 
>> code treating the mechanical deformation of the mesh. Usually, we 
>> define to groups of elements: the bulk of the plate and the holes. We 
>> define the velocity and density in each model. We would like by now to 
>> use the deformation field computed from Code_Aster at each element of 
>> the mesh used in both codes to define the velocity field input in 
>> Specfem2D. Do I have to use as many models in my ParFile as the number 
>> of elements or is there a simpler way to use the deformation field as 
>> an input of SPECFEM?
>> Thank you for your help.
>>
>>
>> Cordially,
>>
>>
>> -- 
>>
>> Jérôme AZZOLA
>> Doctorant en géosciences
>> Tél : +33 (0)7 68 54 92 57
>> azzola at unistra.fr <mailto:azzola at unistra.fr>
>> jerome.azzola at gmail.com <mailto:jerome.azzola at gmail.com>
>> www.unistra.fr <http://www.unistra.fr>
>> EOST - Ecole et Observatoire des Sciences de la Terre
>> 5, rue René Descartes
>> F - 67000 Strasbourg
>>
>>
>>
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>>
> 

-- 
Dimitri Komatitsch, CNRS Research Director (DR CNRS)
Laboratory of Mechanics and Acoustics, Marseille, France
http://komatitsch.free.fr