[CIG-SHORT] step14 friction negative

[Birendra jha]

Hi

Step 14 example: This is an example with a rate and state fault in a quasi-static simulation. 

Q1. I want to check the evolution of the friction coefficient. When I calculate the friction coeff in paraview calculator as follows

mu = 0.4+0.002*ln(mag(slip_rate)/2e-11)+0.08*ln(2e-11*state_variable/0.05)    

where 0.4 is the reference friction coeff. Above equation shows that mu becomes negative when rupture happens. What am I doing wrong here?

Q2. When I plot shear traction vs normal traction at a point in the middle of the fault, I see that the shear tractions increase above 0.4 x normal traction, where mu_0= 0.4. Why is so?

Thanks
Birendra