Dust surface density for micron- (upper) and millimetre-sized particles (bottom), assuming two planets interacting with the disk at 5 AU and 17.5 AU and after 1 Myr of dust evolution. Two different thresholds are considered for the fragmentation velocity of particles v_f = 10 m s^-1 (left) and v_f = 30 m s^-1 (right). The vertical lines correspond to the positions of the two planets.