Some questions about the simulation results

PyLith
1

Hi there，
Recently, I wanted to do a simple test of the stress distribution within the lithosphere. I give the viscosity in advance, I give the force by Neumann boundary conditions, and I look at the effect of viscosity on the force component.
The results were as I expected: higher stresses at the top of the viscous upper mantle and lower stresses at the bottom of the lower crust.

image
image794×531 18.8 KB

But at the same time I have some questions:

  1. I found that the simulation results did not change during the simulation time.
  2. In the crust, the obvious viscosity difference between the bottom of the upper crust and the top of the lower crust should also produce obvious changes in stress, but the results show that the stress in the crust is gradually reduced.
    Does anyone have a similar problem or give me some advice?
    HangWu
    2023/12/28
    gravity_infstrain.cfg (2.4 KB)
    pylithapp.cfg (7.6 KB)
2

What is the Maxwell time corresponding to the viscosity? The shear stresses should relax over a time scale of several times the Maxwell time. The axial stresses will not change as much.

3

I rechecked the results, and all the outputs, including shear stress, did not change with time.
Maxwell time as follows ：
image

4

This indicates the shortest Maxwell time is about 8e+12 seconds (2.5e+5 years). The duration of your simulation is 2.0e+3 years or about 0.01 Maxwell times. Consequently, there is negligible relaxation of the shear stress.

5

Thanks！ I thought there was an error in the simulation process, ignoring the physical parameters.