As a maternity hospital midwife, Yukie Aoyama felt a powerful sense of duty that overrode her fear when the city of Shiogama, Miyagi Prefecture, was struck by the huge earthquake and tsunami that devastated parts of the Tohoku region in March 2011.

"We would have died if the tsunami had been higher than 10 meters," Aoyama, 53, said, recalling the escape of some 50 pregnant women and hospital staff to the top floor of the three-story building.

Aoyama was taking a nap at home before her night-shift when the magnitude-9.0 earthquake struck shortly before 3 p.m. on March 11.