The Japanese archipelago is located in the subduction zone of four tectonic plates (Eurasian, Pacific, Philippine and North American), and is more prone to earthquakes than any other place on our planet. If the Eurasian and North American plates are relatively calm, then the Pacific plate is sliding under the Philippine plate at a speed of 9 cm per year, forming an active subduction zone. This process of plate movement is not very smooth. The lower, heavier plate constantly pulls the upper one, which periodically springs, causing powerful earthquakes. The water above the moving plates receives a strong impulse, forming tsunami waves.
Volcanic processes are another cause of seismic activity in Japan. 10% of all volcanoes on our planet are located on the territory of the archipelago. More than 40 of them are active, while around 160 volcanoes are dormant. Many of the active volcanoes are located near major Japanese cities. Japan, unlike other regions, due to its numerous seismic zones, is prone to earthquakes that can cause significant damage.
Earthquake-resistant construction
One of the ways Japan adapts to devastating earthquakes is the implementation of seismic construction technologies. Japanese building standards are considered the most stringent in the world, are often revised, and buildings are constantly being repaired taking into account the existing seismic risks.
Although ideas for earthquake-resistant construction have existed in Japan for a long time, active research in this field began after the Tokyo earthquake in 1923. The natural disaster claimed the lives of more than 100, 000 people and completely destroyed the cities of Tokyo and Yokohama.
Most of the ruined buildings were constructed of brick according to Western standards. As a result, a year later, seismic regulations were introduced into Japanese legislation, which had to be followed during the construction of new buildings. Since 1950, Japan has established seismic safety standards for high-rise buildings to withstand the strong tremors that could hit the region at any time.
Seismic construction methods
Japan is investing billions of dollars not only in innovative construction, but also in the reconstruction of old buildings to minimize damage from earthquakes. As a result, all facilities and residential buildings in Japan are built using three main seismic protection technologies:
- Taishin – the purpose of this method is to increase the resistance of buildings to shaking and swaying during an earthquake. The walls, columns or beams of such buildings should have a minimum thickness to prevent the collapse. This method is quite widespread in Japan and is especially effective in low-rise construction;
- Seishin – the technique is recommended for the construction of high-rise buildings and is based on the use of dampers between the ground and the building’s foundation. Rubber plates absorb earthquake energy and effectively reduce the intensity of destructive vibrations of building structures;
- Menshin – is the most expensive and technologically advanced method of earthquake-resistant construction of skyscrapers. It is based on the creation of multiple isolation layers separating the building’s foundation from the ground, using lead, rubber and steel. This construction method significantly reduces the effects of earthquakes on the upper floors of the building.
In addition to innovation, the Japanese apply traditional methods of protection that their ancestors have used for many centuries. Thus, the famous Tokyo Skytree tower was built according to the method that was applied in the construction of the 7th century Horyuji Buddhist temple in the ancient capital of Nara. It is considered one of the oldest wooden buildings in the world, and its five-story pagoda, thanks to the original fastening of the central column, has preserved its integrity after numerous devastating earthquakes.
Japan’s strict seismic standards have proven effective in limiting damage and casualties during major earthquakes. Thus, seismic tremors in Chuetsu with a magnitude of 6.8 in 2004 caused the death of 68 people. The 2018 Osaka earthquake with a magnitude of 6.1 caused 43 deaths and minimal damage. A large number of victims of an earthquake with a magnitude of up to 9.1 in 2011off the eastern coast of Honshu was caused by the occurrence of a tsunami wave with a height of 10 m, which claimed many lives, as well as the accident at the Fukushima nuclear power plant.