Variable number of elements in X direction in different layers

[avinash07guddu]

Is it possible to have a different number of elements in the X direction in different layers ?
In the basic example, in the Par file

nx = 80 # number of elements along X

However, this doesn't say it is for which layer.
In the Interface file, different layers can have different number of elements in the Z direction but there is nothing specified about the X direction.

# for each layer, we give the number of spectral elements in the vertical direction
#
# layer number 1 (bottom layer)
 20
# layer number 2
 20

Ideally as the velocities increase with depth, it should be possible to make elements coarser in both X and Z direction to reduce computational effort.
Thanks very much for your help.