Rate-and-state question


Just to understand, if I use the rate-and-state friction model, but set a total simulation time of zero, I would expect the state variable theta to remain constantly equal to the initial value provided in the input file; however, the output value is different to the one in the input file. Could you please explain why ?



If PyLith takes a time step, then it updates the state variables. With a total simulation time of zero, PyLith will still take a single time step.

But if dt=0, theta should not change according to the equations in the manual. Which equation is used ?

dt=0 is nonphysical. What are you trying to do?

Just trying to understand how it works on a simple case, before running more complex cases. I know dt=0 is not physical, but still, according to the equations in the manual, in that case theta should not change.

A better way to understand how rate and state friction works is to generate an example with a steady state solution. If you set the initial conditions appropriately, the state variable (theta) should not change and you should have steady sliding.

There are many issues that can arise with dt=0. For example, the slip rate approaches infinity.