[CIG-SHORT] Slip-weakening friction model for cohesion?

[Brad Aagaard]

On 08/28/2017 04:14 AM, Ekaterina Bolotskaya wrote:
> Dear Pylith developers,
> 
> I'm currently running a 2D simulation which is a 2m (height) by 3m 
> (width) elastic block.
> The block is initially compressed both vertically (2MPa) and 
> horizontally (2MPa) and then sheared with a rate of 0.045 MPa/year for 
> 100 years. Vertical displacement is fixed for all the boundaries: both 
> horizontal and vertical.
> 
> The block has a horizontal fault in the middle which goes almost all the 
> way to the edges of the block (2.98m - fault length).
> I want to have an ~1m long section with a smaller friction coefficient 
> (0.6) in the middle of the fault which would slip first and I want the 
> slip to then propagate to the two side regions that initially had higher 
> friction coefficient (0.8) but that should have same 0.6 coefficient 
> once the slip started happening. I'm implementing this using the 
> slip-weakening friction database.
> 
> I'm now interested in implementing a similar thing with cohesion. I want 
> it to have zero value for the middle section of the fault and some 
> finite value for the two locked (side) sections and then change to zero 
> (for the side sections) in a linear or stepwise fashion as the slip 
> becomes larger than some threshold value (similar to what the 
> coefficient of friction does in slip-weakening model). Is there a way to 
> implement it with Pylith?

The physics you describe is different from the slip-weakening friction 
model implemented in PyLith. As Surendra mentioned, we discuss how to 
add friction models to PyLith in the "Extending PyLith" chapter of the 
manual, which discusses an example in templates/friction.

Regards,
Brad