記事の原文を掲載します。

Japan's earthquake preparation: the country on the Ring of Fire

Japan is an earthquake-prone country. It is notably an area of high seismicity owing to its location near three major tectonic plate boundaries. It is also situated on the Pacific Ring of Fire, which makes it riskier. The deadliest earthquake was the 1923 Great Kanto earthquake, in which 105,385 deaths were reported. However, the strongest and costliest earthquake to date is the 2011 Tohoku earthquake (measuring 9.0), which resulted in losses of more than $235 billion.

More recently, a series of earthquakes at a magnitude 6.2 shook Kumamoto prefecture in the southern Japanese island of Kyushu on April 14. This was followed by another tremor at a magnitude 7.0 that struck the same area in the early hours of April 16.

On the same day, another magnitude 7.8 quake occurred on the opposite side of the Pacific Ring in the coastal provinces of Manabi and Esmeraldas in Ecuador. The death toll reported was more than 40 in Japan and 525 in Ecuador.

Japan employs strong response mechanisms, infrastructure, and training to handle potential disasters in the future. Disaster risk management encompasses both planning for and responding to disasters. In Japan, the planning begins very early, right from schools. Every schoolchild in Japan is made familiar with earthquake drills, which take place as a routine activity every month. Over the past few years, the Japanese government is in the process of enforcing preventive measures to make buildings more resistant to earthquakes in the known disaster-prone zones. Every household in Japan is required to keep a survival kit consisting of water and food to last a few days, a first aid kit, a flashlight, and a radio.

The greatest risk posed by earthquakes is from collapsing buildings. A popular saying among seismologists is: “Earthquakes don’t kill people. Buildings kill people.”
In this context, the buildings constructed on soft soil or on steeply sloped sites in a seismic zone face greater risks. With the onset of an earthquake, the buildings are shaken back and forth. When the shaking finally stops, these buildings either slump into the soil or topple over. The risk is high in case of taller buildings, which may stay intact, but tend to topple over because of unstable foundations. Therefore, the cause of a building collapse depends on the manner in which the structure is built.

Japan has tightened its construction codes and conforms to the world’s strictest construction regulations. All the buildings that were constructed after 1981 were made robust enough to resist a collapse in an earthquake with an intensity of “upper 6” or higher on the scale used by the Japan Meteorological Agency. This agency is in charge of collecting and providing weather data and forecasts in Japan utilizing the data based on the daily scientific observation and research related to the fields of meteorology, volcanology, seismology, and hydrology and other related scientific fields. The construction regulations were further improvised after the occurrence of the quake in Kobe in 1995.

Revisiting and strengthening building regulations from time to time has sharply reduced both the rate of collapsed structures and damage caused. For instance, in the March 2011 earthquake that struck off the Pacific coast of Tohoku, most newer buildings endured the strong tremors.

Ecuador, another earthquake hotspot, introduced stringent seismic regulations after the Haiti earthquake in 2010. However, Hugo Yepes, a geophysicist at the National Polytechnical University in Quito, has raised concerns that builders and developers have been mostly ignoring the authorities with respect to the implementation of seismic regulations. In addition, there are reports that some local officials have effectively legalized informal new neighborhoods without insisting or advising on the anti-seismic standards. On a visit to the area, Rafael Correa, President of Ecuador since 2007, mentioned that the new improvised building standards had to be applied in a more rigorous manner in order to prevent large scale destruction in the future.

Some of the regulations being implemented in Japan include the classification of land for urban development into 12 specific zones starting from” exclusively low-rise residential” to “exclusively industrial” zones. For each zone, factors like permissible limits of development on the land, building size and density, and height are established. The building coverage ratio (BCR) is defined for each zone that legalizes the maximum portion of the land that can be built upon.

However, better building is not the only important activity to focus on. Japan has spent a huge amount of money in the Tokai region and elsewhere on making continuous attempts to forecast the earthquakes and evacuate those areas beforehand. Similarly, in Ecuador, the government is funding a research by an “earthquake whisperer” who claims to be able to detect quakes three days in advance. However, no published studies have yet supported this remarkable claim. Many scientists are skeptical about the claims regarding earthquake predictions.