Question about benchmark TPV 25

Dear Brad,
In SCEC code-comparison exercise, the results of TPV25 are quite different when the conditions at the fault junction are changed. The connected branch fault allows the rupture to slip at the junction and thus has ability to fully rupture. Does pylith supports such connected branch fault model?

PyLith can handle T intersections of faults.

Typically for a fault branch, we create the main (through-going) fault first and then the branch fault. The branch fault must be clamped (no slip) at its intersection with the main fault. The clamping is done by including the intersection in the buried edges. This results in the following geometry:


The “main” fault is A-B-C and the branch fault is B-D. The vertices at B are included in the buried edges for the branch fault. Slip can occur anywhere along A-B-C on the main fault. Slip can occur on the branch fault B-D except at B.

Alternatively, the branch fault can be B-C. That is, one can first create the main fault A-B-D and then the branch fault B-C with B again being in the buried edges for the branch fault B-C. This would allow slip anywhere along the main fault A-B-D and slip on the branch fault B-C except at B.

When I say, create the main fault first, I mean list it first in the PyLith parameter file. PyLith will create faults in the order they are listed in the interfaces array.

Thanks for your help. You used the command group "branch_fault" remove node in main_fault in createbc.jou file of TPV24. If I include the intersection in the buried edges rather than remove it from branch fault, then I can create a connected fault model. Is that right?

Hi, Brad. I created a fault model as you described. I set the A-B-C as the main fault and B-D as the branch fault with vertices at B included in the buried edges. But I found that B-D is still disconnected with the A-B-C and can only be dynamic triggered by the rupture on main fault. I am wondering that if I run two simulations with A-B-C and A-B-D respectively and then combine the results of A-B-C and B-D, could it equivalent to a connected fault model?

In PyLith v2.2 when creating the branch_fault nodeset, you do not need to remove the nodes in the main_fault nodeset; that only applied in versions of PyLith before we implemented buried edges. The nodesets for the two faults will overlap at the intersection; the nodes in the intersection should be included in the bured edges nodeset for the branch fault.