Nearly three out of four wooden houses in Japan would be unlikely to withstand a major earthquake, according to a survey released Friday by a government-authorized association.

The survey, conducted by the Japan Wooden Housing Earthquake Resistance Enhancement Construction Contractors Association, examined 74,327 wooden houses nationwide over a six-year period that began in 1998.

About 50 percent of the houses under scrutiny would be in danger of collapsing if a quake registering in the upper 5 level on the Japanese seismic scale to 7 were to hit the country. Meanwhile, a further 24 percent would be somewhat in danger of collapsing.

A quake of this intensity can cause plates and books to fall off shelves.

The survey also found that 60 percent of houses built after 1981 would be in danger of collapsing, even though mandated quake-proof standards were tightened that year.

"Many houses even built after 1981 are not resistant to quakes because their walls are not well balanced," remarked one official at the Tokyo-based association.

Two-thirds of the houses with quake-resistant problems are located in Hokkaido and the Kanto and Tohoku regions, the association added.