Pylith quasistatic rate-and-state

Dear Pylith Developers,

How does Pylith handle slip rate and thus theta evolution in quasistatic simulations?
Is the slip rate considered zero and theta just evolves as time?

I can provide calculation details, if it helps, but the question is generic.
Thanks!

See slide 14 in from the 2017 tutorial on friction https://wiki.geodynamics.org/_media/software:pylith:tutorials:cdm2017:pylithtutorial_friction.pdf.

We use a linear approximation at very low slip rates. Because we use an iterative solver, to detect actual stick behavior (with any friction model), we use a zero tolerance for detecting slip. If the slip is below this tolerance, it is set to zero. So you are correct in that quasistatic simulations will be locked when the slip / slip rate drops below the zero threshold. The state variable will continue to evolve according to the constitutive equations.