[CIG-SHORT] a PyLith question

[Charles Williams]

Hi Eunseo,

I'm glad it worked.  I'm including cig-short on this because this is the sort of question that could be useful for everyone.  Strain weakening might also be useful, but I haven't put that into the plasticity model yet.  It's been on my list for a while, but the Christchurch earthquake has kept me busy recently.  If you try putting in plasticity, I will be interested to hear what happens.

Charles


On 30/03/2011, at 3:34 AM, Eunseo Choi wrote:

> Hi, Charles, 
> 
> It worked! After the line of shared nodes was removed, the calculation went through and the displacement solution is pretty much as expected.
> 
> However, stress field is dominated by that around the gap between two faults. Displacements also seem affected there.
> Although not completely sure to what degree this is artificial, I guess this is why you suggested to have a weak region or plasticity.
> If plasticity is added in for the purpose of reducing the effect of fault gap, would it be better to have strain weakening, too?
> 
> Eunseo
> 
> 
> On 03/28/11 14:18, Charles Williams wrote:
>> 
>> Hi Eunseo,
>> 
>> It's good to hear from you.  Unfortunately, when we were first designing PyLith, we realized that intersecting faults was a major problem.  There were problems with splitting such faults into cohesive cells in a consistent way, and also deciding how fault slip should be allocated in such a situation.  The simplest solution was simply not to allow intersecting faults.  For most problems, this isn't an issue.  I can't remember for sure, but I believe that a cell can have vertices on more than one fault, but a single vertex cannot lie on more than one fault.  In some cases you may want to include a weaker region (or maybe plasticity) in the region between the two faults.
>> 
>> With a brief glance, your .cfg file looks OK; however, I suspect your problems are due to faults sharing a vertex.  As a test, try eliminating the line of nodes shared by both faults from one of the faults and see what happens.
>> 
>> I hope this answers your question, and I hope this doesn't cause problems in your modeling.  What sort of problem are you trying to solve?
>> 
>> Cheers,
>> Charles
>> 
>> 
>> On 29/03/2011, at 7:06 AM, Eunseo Choi wrote:
>> 
>>> Dear Charles,
>>> 
>>> I hope everything is going well with you.
>>> 
>>> I am trying to see if PyLith can handle stray faults.
>>> For instance, a fault system composed of a major strike-slip fault and a branching one (fault1+fault2 as in the attached figures).
>>> 
>>> Using Cubit, setting up the geometry I want was straightforward but the generated mesh appears to be incompatible with the assumptions made by PyLith. The complaint from PyLith was "Invalid orientation in fault mesh".
>>> 
>>> I wonder if there was any missing step specific to creating a mesh with fault planes intersecting each other; also if it is correct to list two faults as in the attached input file.
>>> 
>>> Please just let me know if you need more information.
>>> Thanks.
>>> 
>>> Best regards,
>>> Eunseo
>>> 
>>> -- 
>>> =====================================
>>> Eunseo Choi
>>> Post-Doctoral Research Scientist
>>> 
>>> Lamont-Doherty Earth Observatory
>>> 305c Oceanography
>>> P.O. Box 1000
>>> 61 Rt. 9W
>>> Palisades, NY 10964-8000
>>> 
>>> http://www.ldeo.columbia.edu/~echoi
>>> Phone: 845-365-8813 Fax: 845-365-8156
>>> =====================================
>>> 
>>> <Halfsine_Vertical_Splay.cfg><fault1.png><fault2.png>
>> 
>> Charles A. Williams
>> Scientist
>> GNS Science
>> 1 Fairway Drive, Avalon
>> PO Box 30368
>> Lower Hutt  5040
>> New Zealand
>> ph (office): 0064-4570-4566
>> fax (office): 0064-4570-4600
>> C.Williams at gns.cri.nz
>> 
>> Notice: This email and any attachments are confidential. If received in error please destroy and immediately notify us. Do not copy or disclose the contents.
>> 
>>  
> 
> 
> -- 
> =====================================
> Eunseo Choi
> Post-Doctoral Research Scientist
> 
> Lamont-Doherty Earth Observatory
> 305C Oceanography
> P.O. Box 1000
> 61 Rt. 9W
> Palisades, NY 10964-8000
> 
> http://www.ldeo.columbia.edu/~echoi
> Phone: 845-365-8813 Fax: 845-365-8156
> =====================================

Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt  5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz

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