The hinge of the subduction zone is not fixed: rollback is when the subduction zone rolls over the overriding plate causing shortening

The hinge of the subduction zone is not fixed: rollback is the retreat of the slab away from the subduction zone due to the sinking, and this causes shortening in the overriding plate when the advance of the overriding plate is slower than roll back

The hinge of the subduction zone is not fixed: rollback is the retreat of the slab away from the subduction zone due to the sinking, and this always causes extension in the overriding plate

The hinge of the subduction zone is fixed in space: rollback is forced by the retreat of the subducting plate when the advance of the overriding plate is slow

The hinge of the subduction zone is not fixed: rollback is the retreat of the slab away from the subduction zone due to the sinking, and this causes extension in the overriding plate when the advance of the overriding plate is slower than roll back