Why is it advisable to use low alloy steel than carbon steel, as concrete reinforcement in an areas that are prone to earthquakes?

i think alloy steel is better than carbon steel , carbon steel is more tougher and would break and crack during strong earthquakes while you need something more elastic during earthquake , some buildings now use wood too for this issue "i.e earthquake" , read this article http://www.all-science-fair-projects.com/print_project_1443_148 , if there is more to added kindly write to me  :) .

thanks