[CIG-SHORT] Stress issue with spherical model

[Brad Aagaard]

Demian,

We will try to look into this next week.

Regards,
Brad


On 11/24/16 8:40 AM, Demian Gomez wrote:
> Dear all,
>
> I think I found the problem with the lithostatic stress in my spherical
> model. I'm not sure if it's a bug or not. I am specifying the stress
> using a SpatialGridDB in lat lon h, where I declare my coordinate system as:
>
>   cs-data = geographic {
>   to-meters = 1
>   space-dim = 3
>   ellipsoid = sphere
>   datum-vert = ellipsoid
>   is-geocentric = false
> }
>
> In pylithapp.cfg I declare my coordinate system as:
>
> [pylithapp.mesh_generator.reader]
> coordsys = spatialdata.geocoords.CSGeo
> coordsys.ellipsoid = sphere
> coordsys.datum_vert = ellipsoid
> coordsys.is_geocentric = true
>
> The problem seems to be that Pylith is still using an ellipsoid instead
> of using ellipsoid = sphere for the SpatialGridDB (I think). I verified
> this by doing the following two experiments (see attached PDF):
>
> 1) I've created the spatialdb by calculating the lithostatic stress on a
> lat lon h grid.
> 2) Same as before but this time I added a stress "offset" of 10 m
> (offset = 10*g*rho). This is equivalent to radially scaling the spatialdb.
>
> From the attached figure, you'll notice that in experiment 1, the
> displacements are 0 at the center of the domain (the picture shows the
> domain cut by a plane). In experiment 2, which has the stress offset,
> the center of the domain shows displacements pointing towards the
> geocenter (stress defect) and a zero displacement ring around the center
> of the domain. Moving away from this ring (towards the edge of the
> domain), there is a region where the displacements point up, showing an
> excess of stress. I've depicted each experiment schematically in the figure.
>
> Would it be possible to verify if what I found is correct? Or maybe
> there's something wrong with my configuration.
>
> Thanks!
> Demián
>
> --
> *Dr. Demián D. Gómez*
> Postdoctoral Researcher
> The Ohio State University - School of Earth Sciences
> 275 Mendenhall Laboratory
> 125 South Oval Mall
> Columbus, Ohio 43210
> Cell: +1 (901) 900-7324
> email: gomez.124 at osu.edu <mailto:gomez.124 at osu.edu>
>
>
>
>
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