[CIG-SHORT] RELAX Question

[Austin Madson]

Prof. Barbot,

Thanks for the response and the example data. I am working out my
parameters (and units now). I think I have a lock on the elastic and
viscoelastic params. However, I am having trouble with the load parameters.

I see that on some of your input files the surface load/traction parameters
are;
nb x1 x2 length width t3 T phi

and another has;
nb x1 x2 t3 length width T phi

I assume the former is correct, yes?

Also, I'm trying to wrap my head around the units for force(t3). In the
GRACE example (the _km.xyz file), the z is used in the following
calculation ($3*9.8/3e10) in order to get force(t3). What are the initial
units in the _km.xyz file for the third column, z? And what are the units
after the calculation ($3*9.8/3e10) in order to derive force(t3)?

Also, it appears that the output vertical (z) displacement units are in mm,
may I assume that is correct?

Cheers and thanks A LOT for your responses!
Austin M

On Tue, Jan 19, 2016 at 9:29 AM, Sylvain Barbot <sylbar.vainbot at gmail.com>
wrote:

> Hi Austin,
>
> The Tibet lakes have a great loading signal. You can use Relax to
> simulate the deformation, but you need to be careful about how
> important the elastic stratification is. If your data are close to the
> source, you're fine. I presume you are using paleo-shoreline data. If
> so, use the shallow rigidity for the entire domain. If you are
> modeling far-field data, you should use a code that have a layered
> elastic structure, i.e., (Farrell, 1972).
>
> The example attached models the deformation from the Indian monsoon
> using Grace data. The example cycleload.sh creates a periodic surface
> load.
>
> Best wishes,
> Sylvain
>
>
>
> On Tue, Jan 19, 2016 at 10:51 AM, Austin Madson <amadson at ucla.edu> wrote:
> > Professor Barbot,
> >
> > Thanks for the prompt response. I looked at the documentation and the man
> > page (as well as the examples on the PDF on the geodynamics website) and
> > have made progress.
> >
> > As an fyi, we plan on modeling several hundred years of surface loading
> from
> > very large lakes (i.e. time dependent loads). Are there any RELAX surface
> > load examples laying around (they can just be single/multiple point and
> even
> > instantaneous (no time function)? The GRACE example on the example pdf
> > "hides" the data in various dat files (which makes sense if you're using
> a
> > lot of data, but it's hard to see their example inputs).
> >
> > I expect to see only millimeters of deformation throughout the run - will
> > the outputs be precise enough if I use the correct SI units throughout?
> >
> > Cheers,
> > Austin Madson
> >
> > On Sun, Jan 17, 2016 at 4:06 PM, Sylvain Barbot <
> sylbar.vainbot at gmail.com>
> > wrote:
> >>
> >> Hi Austin,
> >>
> >> The details of the input file for surface loads are in the documentation
> >> and in the man page. There are some pdf files on the geodynamics website
> >> that show examples of surface loads for the Himalayan region if I recall
> >> well.
> >>
> >> But the input file simply expects a list of squares with their
> associated
> >> traction. So depending on your project, this can be a single point, say
> to
> >> represent the loading of a dam, or a complicated function of space and
> time.
> >> If your change of load is instantaneous, you need only one event. Of
> your
> >> load is time dependent, you need as many events as you have time steps.
> I
> >> can be more specific, but I need more information about your practical
> >> goals.
> >>
> >> Cheers,
> >> Sylvain
> >>
> >>
> >> On Monday, January 18, 2016, Austin Madson <amadson at ucla.edu> wrote:
> >>>
> >>> Professor Barbot,
> >>>
> >>> I have a quick question re: RELAX - Is there any more information out
> >>> there with respect to utilizing RELAX for deformation responses to
> surface
> >>> loading? I have looked through all of the examples as well as the
> >>> slides/tutorials on the geodynamics.org website.
> >>>
> >>> Can you provide any further information? Or can you point me in a
> better
> >>> direction?
> >>>
> >>> Cheers,
> >>> Austin Madson
> >
> >
>
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