GEOLOGY-GEOGRAPHY-NATURE
Living With Earthquakes in Japan
The Japanese Creed: Prepare to Live, Live to Prepare
Earthquakes are a part of everyday life in Japan and have been inflicting pain and suffering for thousands of years. It is impossible to predict where and when the next damaging earthquake will strike Japan, but it will happen, without a doubt. So, how do the Japanese cope with this inevitability and minimize the catastrophic effects of the next quake?
Shaky Ground
The islands of Japan are situated in one of the most seismically active zones in the world, where four tectonic plates converge. Approximately 1,500 minor quakes are recorded in Japan in a typical year. That means that on average, somewhere in Japan, four earthquakes occur every single day. Tremors usually occur in different regions and are not felt across the entire country simultaneously. Sensitive seismographs located throughout the country will detect almost continuous shaking, but that activity goes largely unnoticed by the public.
Daily seismic events may rattle some nerves and cause some minor damage, but periodically Japan is hit with larger events that cause major destruction. It is an accepted facet of life. The people cannot live in fear, so they focus on preparing for the inevitable, with the diligence and technology that the Japanese are famous for. What are Japan’s greatest vulnerabilities and how has it been mitigating the damage and loss of life from earthquakes?
Vulnerabilities
Building standards have become more stringent over the decades, as technology has improved and lessons are learned from each devastating earthquake. Still, in major cities like Tokyo and Osaka, there are neighborhoods consisting of older wooden houses that are particularly vulnerable. These areas of densely-clustered wooden houses have maze-like narrow streets that prevent easy access for emergency vehicles.
Fires that rage after the earthquake, fanned by strong winds, are a primary threat. Many of the homes have portable oil or electric heaters and cooking stoves that catch fire after falling over. To make matters worse, some neighborhoods with wooden and light steel structures are located in alluvial plains and river valleys with thick layers of soft sediments, susceptible to ground failure during a quake.
The Government regularly publicizes what it determines to be high-risk zones, including estimates of the loss of life and structural damage that would result from various scenarios. A report in July 2023 estimated more than 6,000 deaths and 200,000 buildings catching fire or being destroyed from a 7.3 magnitude quake centered near Tokyo. These are dire but sobering warnings for a city that was left in ruins just over 100 years ago in the 1923 Great Kanto Earthquake.
Better Buildings
For decades, Japanese engineers have been incorporating new technology into the design of skyscrapers, to increase seismic resistance. The Toranomon Hills Mori Tower in Tokyo contains shock-absorbing systems using 516 oil dampers with 66” long cylinders. The back and forth motion of the building drives the pistons in and out of the cylinders, which absorb the earthquake’s energy.
Another innovative technique utilizes a weighted structure called the “Active Mass Damper” near the top of the building to help reduce the swaying due to shaking or high winds.
Unfortunately, many tall buildings were built long before these technologies were developed, leaving them at risk. So, one solution has been to install pendulums at the top of an existing building. The 55-story Shinjuku Mitsui Building (which swayed more than six feet during the 2011 Great East Japan Earthquake) was outfitted with six pendulums, each hung inside its own frame and weighing 300 tons. This system is expected to reduce the amount of swaying by 60 percent and also reduce the duration that the building sways.
Over the last several decades, areas within the Tokyo metro with small, aging buildings have been re-developed. These urban centers are designed to be cities within cities; providing open space/parks, residential, retail, offices, and connections to public transit. They are touted as a place where residents will escape to for safety, rather than flee from, during an earthquake.
A tower in Roppongi Hills has a network of gas-powered generators located six levels below ground to ensure a reliable supply of power to the entire Roppongi Hills development for at least 72 hours. These urban communities have emergency supply rooms filled with stacks of boxes containing vital supplies. There also are about 400 warehouses used by local authorities throughout Tokyo to stockpile 9.5 million instant meals of rice, noodles, and biscuits.
Shinkansen: Stopping a Bullet
It may seem a bit foolish for a nation with intense seismic activity to have dozens of Shinkansen (bullet trains) zipping everywhere at over 150 mph on thin metal rails. But since operations began in 1964, Japan’s high-speed rail has maintained an impeccable record of zero injuries and fatalities throughout numerous major earthquakes.
From the beginning, engineers knew that it was essential to equip the shinkansen with an early-warning earthquake detection system. When the first slight tremors from seismic waves are detected, electrical power is shut down and the emergency brakes are activated to significantly reduce the speed of the train before the major tremors strike.
For a train to run at high speeds, the line must be designed with very gradual changes in elevation, long sweeping curves, and no intersections with other transit. This has required a huge number of bridges and elevated railway sections. During the 1995 Great Hanshin-Awaji Earthquake in Kobe, elevated rails of the shinkansen collapsed, causing massive damage (but no train deaths). To mitigate future damage, engineers retrofitted existing rail bridges by reinforcing the bridge piers with steel plates. Since the improvements were made, no bridge piers have been seriously damaged in major earthquakes.
Railcars and tracks have also been equipped with derailment-prevention devices. These combined measures were put to the test during the 2011 Great East Japan Earthquake. All twenty-seven trains in service at the time stopped safely the moment the earthquake hit, proving the efforts successful in ensuring safety.
Beefy Bridges
Even a casual observer walking around in Japan will notice the unique seismic-resisting components of Japan’s bridges and elevated roadways. Some of these were developed in response to the 1995 Hanshin-Awaji Earthquake, in which a significant length of the elevated roadway collapsed.
For example, restraining chains are being used to connect the main bridge girders and the concrete substructure, to prevent unseating of the superstructure. Another technique is to longitudinally restrict the movement of steel bridge girders by connecting them with thick cables. Generally, the concrete and steel columns supporting bridges in Japan are much more robust than what you’ll see in other countries.
When the Hanshin-Awaji Earthquake struck in 1995, the Akashi Kaikyo suspension bridge was under construction. This engineering marvel, connecting Kobe to Awaji island, is one of the longest suspension bridges in the world today. When the earthquake struck, the massive foundations and towers had already been completed but the epicenter of the earthquake was directly underneath the Awaji side of the bridge.
Investigations were undertaken afterward and it was determined that no damage had occurred to the already-erected structures. However, the survey results showed that one of the towers shifted about five feet. This increased the length of the center span by about one meter (over 3 ft), which had to be accounted for when completing the superstructure of the bridge.
Prepare to Live; Live to Prepare
Japanese society is well known for its meticulous habits of analyzing, organizing, and preparing — to the point that most foreigners would consider slightly painful. Japan has a strong and dominant government that leads its citizens with a plethora of guidelines, rules, and restrictions. The citizens, in turn, put a lot of trust in their government and are largely obedient.
This is evident in the lengths that Japan goes to in preparation for earthquakes. Contrast this with a country like Turkey, which suffered a horrible earthquake in 2023. The aftermath in Turkey was filled with chaos and finger-pointing due to political instability and corruption; the people had little faith in their institutions.
Starting in the 1960s, the Japanese government began actively implementing measures to shore up both the physical and institutional safeguards against disasters, with particular emphasis on disaster prevention.
However, Japan didn’t significantly ramp up its procedures until after the Great Hanshin Earthquake in 1995 when more than 6,000 people died. In that event, the government was criticized for its initially slow response. The yakuza (organized crime syndicate) stepped into the void and was actively involved in the relief effort from the beginning, distributing substantial amounts of food and supplies to needy victims.
Also, volunteers from all over Japan (about 1.2 million) converged on the Kobe area to lend assistance. This event is often regarded as the start of volunteerism as a major form of civic engagement. From that point forward, the national and local authorities, neighborhood associations, community-building councils, and businesses have all been actively involved in disaster prevention and response.
Japanese cell phones are equipped with an earthquake alert system that gives users a 5 to 10-second warning to seek shelter before an earthquake strikes. The Japan Meteorological Agency (JMA) uses a Seismic Intensity Scale called shindo.
This system is unique to Japan because it categorizes the intensity felt at measurement sites distributed throughout the affected area. In contrast, other countries focus on the magnitude, which is reported as one number representing the energy released by the earthquake. So, when residents of Japan feel tremors, they naturally want to know the earthquake’s epicenter and severity. That information, including the intensity observations throughout the region, is automatically calculated and posted on JMA’s website within a few minutes of the earthquake striking.
This happens every day, several times, throughout Japan. If the earthquake is fairly high in intensity, all of Japan’s TV channels will immediately switch to official earthquake coverage, ensuring that the population is well-informed.
Living with and reacting to earthquakes is now ingrained in the Japanese way of life. From disaster drills on the first day of kindergarten, to millions of participants in National Disaster Prevention Day, the message is the same:
-be prepared for the worst
Resources: phys.org, euronews.com
