The strange topography

Hi all,
Recently, I want to test a model about Eastern Tibet include a weak lithosphere (left) and a strong lithosphere (right). As mentioned in much of the literature, this lateral difference in viscosity may be one of the causes of steep topography.
To ensure equilibrium, I gave an initial topography of 1.8km for the left plateau.
But I checked the final output of the terrain data and found the following problem:

1、In the middle of the model, it also shows significant negative topography, and the difference in topography reaches more than 8km, which is a large difference from the actual. (as follow figure)
2、It seems to me that the weak lithosphere on the left side should be uplifted as a whole, and the lithosphere on the right side is difficult to deform significantly because it is stronger.

Can anyone give me some advice?

Eastern_Tibet.prm (7.7 KB)
topography.txt (3.6 KB)

Hi @HangWu,

Thank you for posting the question to the forum. If plot velocity vectors on the images above, I suspect what you may see is flow in the asthenosphere that drives the evolution of topography to its current state.

Designing models with initial topography or lateral variations in lithospheric structure with a free surface is quite challenging. This is in part due to the fact that even if ensures isostatic equilibrium at a given depth by adjusting by surface topography and subsurface structure, there will be missing variations in elastic stress that would also act to support topography.

To assist further, it would be helpful to know exactly what hypothesis and processes you are trying to model. Is the goal to understand what lithospheric structure and rheology will reproduce current topographic patterns, or are you interested in the evolution of how topography will evolve from a given set of initial conditions? The model design and assumptions will likely be quite different between these two scenarios.

Aside, I suggest adding velocity vectors to your images and see what is driving the evolution of topography in your current results.