a, 80-Myr-old lithosphere, and b, 120-Myr-old lithosphere, assuming a half-space cooling model; c, cratonic lithosphere, d, transitional lithosphere and e, the lithosphere of the back-arc region which assume a linear geotherm to the internal temperature. In the viscosity plots, the green line is the temperature and the blue line is the viscosity. The averaged, truncated value for each layer is shown by the horizontal bars. The black dashed line is the depth-dependent change in viscosity at the internal reference temperature normalized to the value at the base of the lithosphere. In the density plots, the solid line is the calculated density based on the temperature and composition and the bars are the relative density change from the density at the internal temperature. The strength plots show increasing strength with depth and pressure as separate lines and the actual strength used for each layer as a dark bar. After softening, the yield strength reduces as plastic strain increases following the function shown in f. The final yield strength is shown in the light coloured bars in each of the strength plots. In e there are two strength profiles shown, one for the ‘weak’ case (left) and one for the ‘strong’ case (right). Models 80w and 120w use the weaker profile in this region; models 80s and 120s use the stronger one.