As Japan's record earthquake struck at 2:46 p.m on March 11, Hidenori Tsukatani crawled under his desk and thought to himself: Now we will find out.

Tsukatani, a 60-year-old structural designer at Mitsubishi Jisho Sekkei Inc., has spent 35 years studying ways to make buildings that can withstand earthquakes so powerful they occur only once in every 500 to 1,000 years.

"People experienced such a big earthquake for the first time and felt scared, but the intensity of the quake in Tokyo was less than half of what we had simulated for our buildings," said Tsukatani, a general manager at the unit of Mitsubishi Estate Co., the nation's second-biggest developer. "I remember staying under my desk and watching the walls and the ceiling."