Application here is so notorious, the world's scientists have a nickname for this seismic horror：the Mexico City Effect. In the quest of Mexico city earthquake proof, the shifting earth poses its challenge to every construction project, whether above ground or below. Mexico city has the world's third busiest subway system, behind only Moscow and Tokyo, one hundred and seventy six stations, two hundred and seven kilometers of track, more than four million riders a day. But most impressive is that the system's conquest of the rein.

"When we begun to build the subway ,we discovered that the soil was very muddy, so construction was very difficult." The answer was a construction technique called Milan walls, two parallel trenches dug,then filled with concrete and steel rods to form the subway tunnel 's walls, between these walls, the tunnel itself is dug. But engineers run into an obstacle, a law brought in called Archimedes Principle, the same principle allows the submarine to rise, dive or float, the tunnel had to weigh the same as the earth was escalated, weigh less and it would rise, more and it would sink. Instead the tunnel had to float in the soil, to ensure equilibrium, engineers precisely calibrated the weight of the walls to match the displace its soil. Over the open stations, they made up the difference by putting up buildings, no one knew if the Milan walls withstand the earthquake, then came 1995, the quake leveled the worried hospital, the subway station below, not a scratch, the entire system rolled out the seismic waves by floating in the subsoil, in fact the subway was the only way to reach many disaster zones, yet even there is subway tunnel in advance ,the greatest feat of engineering is happening on the surface.