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

[Surendra Nadh Somala]

The slip weakening friction implemented in Pylith operates on friction
coefficient only.
While variation of cohesion can be specified at time t=0, in the
slip-weakening model of Pylith, it cannot do what you are looking for.

You may have to implement a new friction model, taking the slip weakening
related files in pylith, and code in the new governing equation that you
contact conditions that you wish to specify (i.e., slip-weakening
cohesion?).
For details on how to extend Pylith, you can check the last subsection in
the chapter on 'Extending Pylith' within Pylith manual.

-SS


___________
*Surendra Nadh Somala*
Assistant Professor
Department of Civil Engineering (Block-E, 208)
Indian Institute of Technology (IIT) Hyderabad
Kandi, Sangareddy
Telangana, India - 502285
Phone : +91 (0)40 2301-8457
http://civil.iith.ac.in/surendra/

On Mon, Aug 28, 2017 at 4:44 PM, Ekaterina Bolotskaya <bolee at mit.edu> 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?
>
> Thanks!
>
> Best regards,
> Ekaterina Bolotskaya
>
> PhD in Geophysics,
> Earth, Atmospheric and Planetary Science Department,
> Massachusetts Institute of Technology
> E-mail. bolee at mit.edu
> Mob. +1 (857) 284-2805 <+1%20(857)%20284-2805>
>          +7 (963) 995-36-33 <+7%20(963)%20995-36-33>
>
>
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