[CIG-SHORT] How to determine the value of Up direction

[Brad Aagaard]

Tu Xiang,

Is any part of your fault surface horizontal? If not, then you forgot to 
mark the buried edges of the fault. See Step 2 Error 6 in the PyLith 
Troubleshooting tutorial from CDM2017: 
https://wiki.geodynamics.org/software:pylith:cdm2017.

If your fault surface includes some portions that are horizontal, then 
you need to tweak the up_dir so that CrossProduct((0,0,1),up) != 0. For 
example if your fault dips slightly to the east, then I suggest using 
(-0.1,0,0.9). Note that the up_dir you supply does not have to be a unit 
vector. See Section 6.4.3 in the PyLith manual for more information 
about the up_dir parameter.

Regards,
Brad


On 08/29/2017 03:53 AM, tu xiang wrote:
> 
> 
> Based on the cubit_cellsize example, I construct another fault mesh 
> model. But it output another error.
> 
> 
> RuntimeError: Error computing orientation of cell face. Cannot resolve 
> tangential components into unambigious directions.
> Up direction (0, 0, 1)  cannot be parallel to the face normal (0, -0, -1).
> If the face is horizontal, adjust the up_dir parameter.
> application called MPI_Abort(MPI_COMM_WORLD, -1) - process 0
> 
> The complete output is attached.
> 
> 
> Although I have looked up the manual, I do not know What does it mean 
> and how to determine the value of Up direction.
> 
> 
> Tu Xiang
> 
> 
>