Japan has earned a reputation as one of the most disaster-prepared nations in the world, thanks to its seismic regulations and preparedness culture that is largely built on knowledge from previous disasters, National Geographic reported.
Japan is one of the most seismically active countries in the world. Its location between four tectonic plates means that earthquakes are a matter of "if", not "when". Although they often go unnoticed by people walking above them, seismic tremors are a daily occurrence in the country, which experiences about 1,500 noticeable earthquakes each year, according to the EarthScope Consortium. Given this risk, finding ways to survive earthquakes is woven into the physical and social fabric of Japanese communities.
Adapting to strong earthquakes
"Understanding how best to prepare for major earthquakes is often difficult to achieve based on knowledge gained from past disasters," said Keith Porter, chief engineer at Canada's Catastrophe Loss Reduction Institute. In Japan, seismic codes for building codes were first introduced after a magnitude 7.9 earthquake in 1923 that killed more than 140,000 people and left hundreds of thousands of buildings in ruins. These early regulations aimed to strengthen new structures being built in urban areas by adding oversight to the construction of wood and concrete buildings.
Over the intervening decades, the seismic code has undergone a number of significant changes, most notably through the Building Standards Act of 1950 and the New Earthquake-Resistant Building Standards Amendment of 1981. Along with providing construction specifics, these pieces of legislation set expectations for how buildings are expected to perform during earthquakes. The 1950 law established a standard by which buildings are expected to withstand earthquakes up to magnitude 7 without serious problems. The 1981 amendment was a little more specific about what that damage could be, stating that in earthquakes up to magnitude 7, the building should only sustain minor damage but function as normal. In stronger earthquakes, Japanese law states that the building simply must not collapse.
In Japan, there are a number of different techniques to achieve these standards, and the choice of technique often depends on the type of structure - for example, a skyscraper or a single-family house - and the available budget, as well as other considerations. At the base level, buildings are strengthened with thicker beams, columns and walls to better withstand earthquakes.
There are also techniques to help isolate buildings from the motion of the shaking ground. One popular method is to install pads made of an absorbent material such as rubber at the base of the building's foundations, which dampen the shock of the movement of the structure itself. Another approach, the foundation isolation system, requires not only placing these pads in the foundation, but also building the entire structure on a thick pad so that there is a full layer of separation between the device and the moving ground.
Porter notes that many of Japan's old buildings are of traditional wood post-and-beam construction, which "is usually very fragile" and vulnerable to damage from earthquakes. After another deadly earthquake in 1995, Japan began to focus on modernizing older architecture to make it more earthquake-resistant.
After the earthquake on New Year's Day, University of Tokyo professor Toshitaka Katada said he believed there was "probably no people on Earth who are as prepared for disasters as the Japanese," given the preparedness measures considered routine in the country , such as evacuation planning and drills. Evacuation centers, often schools or other public gathering places, are equipped with emergency supplies, and residents are told to have emergency supplies available in their homes as well. The country also has a robust warning system that was activated for both the earthquake and tsunami threat earlier this month.
Of course, none of this is reliable. Specific challenges arise depending on the location of the building, for example if it is located in a "liquefaction" zone where the soil can no longer support the weight of the structures. There are also secondary effects that often follow large earthquakes, such as the ignition of fires or tsunami damage. /BGNES
