[CIG-SHORT] Rate and state friction friction.linear_slip_rate nondimentional?

[Brad Aagaard]

Ekaterina,

The linear_slip_rate value is used to regularize the log term as slip 
rates approaches zero. It is most closely related to the solver 
tolerances (which are nondimensional), which is why I chose to use a 
nondimensional value. I would try using a value for the linear slip rate 
that is about one order of magnitude larger than your SNES absolute 
tolerance. I would expect these values to be a few orders of magnitude 
smaller than the nondimensionalized reference slip rate. Slip rate is 
nondimensionalized by dividing the slip rate in m/s by the velocity 
scale (length scale in meters divided by the time scale in seconds).

Regards,
Brad


On 02/28/2018 03:50 PM, Ekaterina Bolotskaya wrote:
> Dear Pylith developers,
> 
> I'm using rate and state friction model in my simulations.
> I found in the manual that friction.linear_slip_rate is a nondimentional 
> quantity that should be about one order of magnitude larger than 
> absolute tolerance in solve.
> 
> Could you tell me how Pylith uses this nondimentional value 
> (*friction.linear_slip_rate*) with my dimentional*slip rate* and 
> *reference slip rate*? Or how does it nondimentionalize dimentional 
> rates? And what should the relation between the three approximately be? 
> I just want to make sure the three of them are reasonable with regard to 
> each other.
> 
> Thanks!
> 
> 
> Best regards,
> Ekaterina Bolotskaya
> 
> PhD student in Geophysics,
> Earth, Atmospheric and Planetary Science Department,
> Massachusetts Institute of Technology
> E-mail. bolee at mit.edu
> Mob. +1 (857) 284-2805 <tel:%2B1%20%28857%29%20284-2805>
> +7 (963) 995-36-33 <tel:%2B7%20%28963%29%20995-36-33>