Good afternoon,

I’m running 2D subduction models in ASPECT, where I’m using the “box with lithosphere boundary indicators” geometry model to impose horizontal velocities at the side of the model domain and at lithospheric depths (<= 100 km). Because I have an elongated domain (aspect ratio 1:6; x,y = 5400 km, 900 km), and am using the lithospheric indicators, my problem is that I can’t seem to get square finite elements throughout the entire domain without introducing issues into the subduction model:

If I generate the mesh by choosing 1 repetition along the Y axis, I get square elements in all the domain except in the lithosphere, where the elements are rectangular and with aspect ratio 1:6. In particular:

subsection Geometry model

set Model name = box with lithosphere boundary indicatorssubsection Box with lithosphere boundary indicators

set X extent = 5400.e3

set Y extent = 900.e3

set X repetitions = 6

set Y repetitions = 1

set Lithospheric thickness = 100.e3

set Y repetitions lithosphere = 1

end

end

If I use the lithospheric thickness as a scaling factor, and have 9 repetitions along y and 54 along x, i.e. replacing the corresponding two lines with the following:

`set X repetitions = 54 set Y repetitions = 9`

I do get the square elements, but inflow boundary conditions do not work as expected (horizontal velocity is no longer imposed at just lithospheric depths) . The prm files I used for these two tests (attached) are identical except for the X, Y repetitions I reported above.

rectangulat_elements.prm (9.8 KB)

square_elements.prm (9.8 KB)

Do you know what the issue is here? Any help would be highly appreciated.

Thanks,

Valeria Turino