Challenges for the Next Generation of Seismic Codes - Earthquake Engineering for Structural Design - page 461

10.2.3 Japan
The modern era of Japanese building construction can be considered to have its
origin after 1868, during the Meiji restoration, a period when Japan was eager to
embrace aspects of foreign culture and science, including the adoption of some
foreign building construction practices. The AIJ (Architectural Institute of Japan)
was formed in 1886 and the first city planning legislation was issued in 1888. The
formation of the Earthquake Investigation Committee following the 1891 Nobi
earthquake was an early step toward the development of modern earthquake
resistant construction technology in Japan. Observations on the building
performance under earthquakes during this period strongly influenced the modern
earthquake engineering construction (Whittaker et al, 1997).
Seismological aspects. Japan is geographically located in a very complex and
active seismic zone, composed by principal and secondary fault systems. The
principal system consists in the zone where the Amur microplate (as the Eastern
edge of the Eurasian plate) meets the Okhotsk microplate (as the Western edge of
the North American plate), the Pacific plate and the Philippine plate. The
movements of these boundaries are characterized by the Philippine, Pacific and
North American plate's subduction under the Eurasian plate, resulting in important
both crustal interplate and deep intraslab earthquakes. This principal fault system is
associated to a secondary system produced by local faults, with more than 1500
active faults reported around Japan. The earthquakes are mainly concentrated in the
Eastern and Northern parts of Japan and few events occur in the Western and
Southern parts of Japan. Due to this very dense fault network, the Japanese
earthquakes can be simultaneously produced by multiple sources. Therefore, in
some cases, the secondary faults (e.g. the Kobe earthquake, where three sources
were active) can be more damaging than the principal fault system. Because of this
very complex fault system, all earthquake types can affect Japan.
Code evolution. The Japanese code was one of the first regulations in the world
concerning the seismic actions. The Urban Building Law and Urban Planning Law
were promulgated in 1920 to regulate buildings and city planning for six cities:
Tokyo, Yokohama, Nagoya, Kyoto, Osaka and Kobe (Otani, 2004). The seismic
building design code started in 1924; then the Urban Building Law was revised as
a consequence of the 1923 Great Kanto earthquake disaster. A new version was
published in 1950, when the Building Standard Law replaced the Urban Building
Law with more elaborate provisions for structural design. Other details of
structural design, such as structural analysis and proportioning of members, were
specified in the Structural Standards issued by the Architectural Institute of Japan
These standards, prepared separately for each structural material, supplement the
law and can be revised more frequently to add new knowledge and provide rules
for new materials as soon as they develop (Kuramoto, 2006). The Building
Standard Law Order, revised in 1963, removed the building height limitation to 45
m and to 60 m in 1981, but with the approval of the Ministry of Construction.
The seismic design building code was radically changed in 1981 in the largest
revision since 1924, after the 1968 Tokachi-oki and 1978 Miyagiken-oki