Japan suffers from frequent earthquakes. It is estimated that about 6,000 earthquakes occur annually. Most of them are micro-shocks, which are often unnoticeable for people, but there are also strong earthquakes that cause huge losses in infrastructure and in human. Therefore, the priority is to search for and implement solutions that will minimize losses and protect the Japanese from this threat. Everyone is responsible for this, the government, private companies and individual citizens. This modern country is full of high buildings and high-speed trains. It would seem that many earthquakes are not conducive to such solutions. One skyscraper near the other one during earthquake. It must be recipe for disaster. However, Japan has been a leader in introducing technologies to counteract earthquakes for years. Many Japanese buildings are equipped with shock-resistant components. Some of them absorb vibrations, while others make the building float on its foundations. But the collapse of buildings is not the only one threat from earthquakes. They can also cause fires related to the failure of electrical and gas installations or cut off the flow of drinking water. And for such threats, solutions are also being sought in Japan. Earthquake resistance technologies aren’t something new in Japan. For thousands of years, Japan has been using techniques to prevent disasters’s effects.
Tōji Pagoda in Kyoto
Anti-shock technologies in Japanese architecture
In Japan, until the 19th century, all buildings were wooden. Since ancient times people have known that materials such as stone and brick are not resistant to earthquakes, that’s why wood was used. In addition, nails or other metal elements were generally not used at all. On one hand, it enabled a quick reconstruction of a building that suffered any disaster, such as a fire. On the other hand, it had an anti-shock effect. Wood has its flexibility, which makes it move slightly during the earthquakes instead of being destroyed. In addition to wood as a building material, additional technologies were also used to prevent collapse. A perfect example of this are the pagodas in Buddhist temples, for example the five-store pagoda at the Tōji Temple in Kyoto, which is 55 meters high. Tall wooden buildings like this one can be found all over Japan, many of them have been digested by fire, but there is no evidence that any damage was caused by earthquakes. Tōji pagoda was last rebuilt in 1644 and has survived every earthquake since then. This is possible thanks to a single pillar that runs through the center of the pagoda and is built deep into the ground. The pillar is not attached to any of the other building elements that surround it. Each of the five floors of the pagoda is supported by independent pillars and other more complicated components. The key to resistance to earthquakes is this single, thick and strong beam, that is, the central pillar. An experiment was even carried out to prove this theory. Researchers built a 1:5 pagoda model to see how damaged it will be by the earthquake. During an earthquake, the central pillar moves strongly to the left and right, but the rest of the structure moves in the opposite direction. These movements cancel each other out, protecting the tower against collapsing.
This brilliant technology is used even today, in modern and much higher buildings. Tokyo Skytree is 634 meters high and is the tallest free-standing tower in the world. And although it is slightly swaying in the wind, it will not break and will not be destroyed, because the Tokyo Skytree used the same principle as in the pagoda. The central pillar also serves as an emergency staircase. It is not connected to other sections of the building, so when it comes to an earthquake, it moves in the opposite direction than the rest of the building, which eliminates vibrations.
Classic Japanese homes are also resistant to earthquakes. The base of foundations of the old houses is built on a bed of stones, above that are pillars and above that is another base so it has two layers. In the foundations there is also a thick beam, which serves as an additional support, and because it is made of such a thick material, it gives the entire construction incredible resistance to earthquakes. Each pillar stands on a stone, so they move along with the earth during an earthquake and dissipating most of the power of the quake. Pillars are shaped to match the stone on which they stand, and each combination of stone and pillar is unique. The pillars are not attached to the ground, so when it comes to an earthquake, they move, but this movement absorbs shocks. Inside the house there is a lintel, which is made of wood, which as we know has a certain flexibility and bends and moves during the earthquake. It is very subtle, but the movements absorb the power of the quake. Lintels are placed in the pillars of the house without nails or screws. If they were nailed down, the nails could fall out during a strong earthquake, disturbing the entire structure. Instead, there is more play in the joints, which gives greater structural stability. Each beam and pillar are carved by hand, which is why they fit together perfectly. The ceiling also has several large beams that reinforce each other.
Earthquakes occur throughout Japan and the strongest cause huge damage. For this reason, the law requires Japanese construction to adhere to a certain level of resistance to earthquakes. The threat is created not only by the falling building, but also by falling elements inside them, such as big furniture. It can also be fatal to people. The higher the building, the more vulnerable it is to earthquakes, and as we know, there are a lot of tall buildings in Japan and new ones are still being built. Modern architecture uses advanced and latest technologies to build buildings resistant to earthquakes. One of the ways is to use reinforced concrete with a special composition, which makes it resistant even to cracks. Depending on the place where it is used, concrete with different viscosity is used. The appropriate viscosity minimizes concrete cracks. This strengthens the structure of the building and minimizes the risk of collapse or fall of a part of the building.
There are also two types of bearings on which the whole building is based. These are steel plates and laminated rubber bearings. These elements are placed in the foundations of buildings and move during an earthquake. In this way, they reduce the amount of shocks to less than 1/10. Thanks to this, even during a very strong earthquake, the building is relatively stable. These elements can move in all directions absorbing vibrations before they reach the building. It lowers the intensity of moving even the highest floors of the building, and significantly slows down the swaying and slows down the building. This prevents damage to the building and protects large items from tipping over.
Another method, which is just in the testing phase, is based on the unusual idea of making a building afloat during the earthquake. A tank with air, which would be located, for example in a residential house, would activate within a second from the detection of a quake and would lift the entire structure over the ground using air pressure.
Technologies against the effects of earthquakes in everyday life
Technologies that prevent shocks and minimize their effects are not only used in construction, but also in everyday life. Even Earthquake Technology Expo is organized in Japan, where the latest ideas are presented.
The latest seismic isolation system looks like thin and light metal plates. When one lies on the other, they are static, but in the case of an earthquake of strength 5 or higher, the upper plate slides over the bottom plate. The same mechanism is used as in the case of bearings installed in the foundations of buildings. The plates can be made to order to fit the required footprint, from small wardrobes or works of art to medical equipment and production lines in the factory. Setting an object on the plates means that during an earthquake, it stays still.
The danger during an earthquake can be also a fire caused by an electricity or gas installations failure. The latest solution are breaker switches designed to detect an earthquake and automatically cutting off the flow of electricity and in turn preventing damage from occurrences like electrical fires. The system cuts off electricity after 3 minutes, so it gives you enough time to evacuate, for example at night.
In the event of a drinking water supply cut-off, a water treatment system was developed with a very efficient reverse osmosis filter that can be used regardless of where the water source is from. This device is also extremely compact, making it easy to store. It receives water from the source and sends it to the cleansing device. The device works even when the electricity is turned off. It can also use the power of human hands because it has an additional manual pump.
One of the problems caused by earthquakes are opening cabinets and sliding drawers. They can strike a man or cause material damage in the form of beaten commemorative porcelain and glass. A solution was also found for this. They are shock-resistant latches installed inside cabinets. Latches have sensors that automatically detect shocks caused by earthquake and activate the door lock. After the earthquake is over, the latches are released automatically and the door opens again freely.
Anti-shock and anti-earthquake technologies accompany the Japanese at every step. Thanks to this, country that experiences almost the most earthquakes during the year is at the same time the most resistant. Natural disasters are not seen as phenomena that cannot be fought. All possible steps are taken to minimize losses.
1. Seismic and Wind Performance of Five-Storied Pagoda of Timber Heritage Structure, Advanced Materials Research Vols. 133-134 (2010) pp 79-95,© (2010) Trans Tech Publications, Switzerland
2. Five-story Pagodas: Why Can’t Earthquakes Knock Them Down? Wisdom from the Distant Past, NIPPONIA No.33 June 15, 2005
3. JAPANESE EARTHQUAKE RESISTANCE AND SEISMIC ISOLATION TECHNOLOGIES, web-japan.org, July 28 2011