Intersting info on Martian Crust

It's difficult to tell specifically how active Martian Crust still is, but from these two fine .pdf's you can read some-what technical material about Crustal mechanics on Mars.

Crustal Dichotomy

Lateral extension of topography to extrapolate Crustal thickness

Both of these discuss well the thickness of the Martian crust with the thinnest section being the Northern Hemisphere having about a thickness of 40km.

Which is significantly thin; but not thin enough (probably) to have Plate tectonics.

However it is still interesting and very informative.