[CIG-SHORT] Frictional behavior and imposed episodic slip on a fault

[Matthew Knepley]

On Thu, Aug 23, 2012 at 10:12 AM, Brad Aagaard <baagaard at usgs.gov> wrote:

> Romain,
>
> The current version of PyLith does not support mixing prescribed slip
> and spontaneous slip on the same fault. I do not know of a workaround
> for the issue of the single cell impeding slip between the two faults.
> Oliver Boyd asked for a mixed fault implementation a few years ago and I
> have some ideas on how it might be possible to extend the current
> formulation to handle this. I have not tried to flush out the details to
> see how practical it is because other features have higher priorities.
>
> In the current version of PyLith, one possible solution would be to use
> a single fault controlled by spontaneous rupture (FaultCohesiveDyn) but
> setup the BC to facilitate episodic slip on the desired portion of the
> fault. This could be done via spatial variation in the friction model
> parameters or Dirichlet BC in the vicinity of the fault. The advantage
> of this approach is that the physics at the intersection between the
> portion with episodic slip and other portion of the fault will be
> consistent.


You could also think about having prescribed fault tractions generate the
slip.

   Matt


>
> Brad
>
>
> On 08/22/2012 07:31 PM, Romain Jolivet wrote:
> > Hello Pylith users and developers,
> >
> > Is there a zero slip condition at the tip of a fault (FaultCohesiveKin
> object) and if yes, is there a way to remove this constraint?
> >
> > I explain my problem a little bit more. Here is a little drawing:
> >
> #-------------------------------------------------------------------------------------------------#
> > |
>                                                             |
> > |                                                                 Medium
> 1                                                |
> > |
>                                                             |
> > |
>                                                             |
> > |                Fault 1
>   Fault 2                                       |
> >
> #--------------------------------#----------------------------------------------------------------#
> > |         imposed slip
>  FaultCohesiveDyn                          |
> > | (1 earthquake/100 yrs)
>                                          |
> > |
>                                                              |
> > |
>  Medium 2                                                |
> > |
>                                                              |
> >
> #-------------------------------------------------------------------------------------------------#
> >
> > I would like to impose slip, episodically, on fault 1 and observe the
> behavior of fault 2, that has a frictional rheology. I apply dirichlet
> boundary conditions on the edges of medium 1 (towards the left) and medium
> 2 (towards the right), so that frictional creep occurs along Fault 2
> between slip episodes.
> >
> > The problem right now is that the element at the junction between the
> two faults (the one that belongs to fault 2) does not slip. Consequently,
> creep does not propagate correctly in fault 2 after each event. Then there
> is a huge stress accumulation at the junction between the two faults (the
> problem might diverge at some point). One solution would be to have one
> fault (FaultCohesiveDyn) and to impose slip on part of its elements. Is it
> possible to impose episodes of slip on elements of a FaultCohesiveDyn
> object?
> >
> > I would like to know if this is possible to do with the latest PyLith
> version, if I need to implement my own fault module (Would it be
> easy/complicated/hard/a nightmare/impossible?) or if I should change the
> design of my problem?
> >
> > Thanks,
> > Romain
> >
> > Romain Jolivet
> > Postdoctoral Scholar
> > Geological and Planetary Sciences
> > California Institute of Technology, Pasadena, CA
> > rjolivet at caltech.edu
> > +1 (626) 560 6356
> >
> >
> >
> >
> > _______________________________________________
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> > CIG-SHORT at geodynamics.org
> > http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
> >
>
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