Discussion about 2-d subduction example 5

PyLith
1

Hi all,

I am working on a 2-d subduction example 5 (step05) using the binary Pylith 2.2.2.
One thing I am surprised about was that I observed a stick-slip system associated with two blocks.

Pylith manual says “In order to generate stick-slip events, we need the coefficient of friction to decrease with slip. We choose a slip-weakening friction model with a dynamic coefficient of friction that is less than the static coefficient of friction to provide this behavior.” in page 180. The example specifies depth-dependent frictional properties with stable sliding (equal dynamic and static coefficients of friction) above and below the seismogenic zone (elevations of -5 km to -45 km).

So, I expected a stick-slip event in the seismogenic zone but I found several small stick-slip events occurred at a deeper portion of the seismogenic zone and then a large stick-slip event followed (see the att.).

It seems like a strong friction coefficient placed at a shallow portion but it is not.

Does anyone know why these phenomena happened?

Thanks

Sungho

slip

2

Two issues that come to mind include:

  1. The resolution of the model is rather coarse (the examples are intended to demonstrate the workflow) so the physical processes and spatial variations in behavior are not necessarily well resolved; and
  2. There can be complex interactions between the loading, creep, and coseismic slip.