Although Japan has always experienced earthquakes, the country’s first seismic code was only set down in 1924 after the Great Kanto Earthquake hit the Tokyo area in September 1923. Sixty percent of the city’s structures were damaged in that catastrophe, and it is considered Japan’s second-worst disaster after the Great East Japan earthquake in 2011. The seismic code is typically revised and strengthened whenever large-scale earthquakes rock the country.
The next seismic code went into effect in 1950 when the Building Standards Law was enforced. The law’s goal was to ensure the safety of human lives by preventing building collapses. However, that law only considered the mid-level earthquakes that occur several times during a building’s service life, ignoring the possibility of large-scale quakes.
Five major earthquakes between 1964 and 1978, however, proved that the seismic code was outdated. Based on an analysis of those quakes, a new seismic code was established in 1981. The code took into account damage caused by soil instability and weak major load-bearing parts such as beams and columns. Other factors assessed included structural deformation, unbalanced structural members, and the relative plasticity of the structure.
To Be Continued