Migration speed vs. time for the six simulation sets. A first phase of inward vortex-driven migration is common to all the cases. Atabout t = 50 000 yr the migration paths bifurcate: for the very thin active layer of simulation S01 the final speed of migration is very similar to the NW case; increasing the depth of the layer a regime of faster inward migration is observed. When the active layer is at the midplane the planet migrates inwards (H_in) and outwards (H_out) at opposite speeds in the final phase of the simulation.