Preparing for major earthquakes that threaten the capital: Tokyo Gas Network's 24-hour monitoring system ensures safety and security of gas supply

A major earthquake directly beneath the capital is anticipated within 30 years with a 70% probability and expected to cause massive damage. Powerful tremors of magnitude 7 will mercilessly strike critical social infrastructure such as electricity and gas. If large gas pipes are damaged and gas leaks out in large quantities, there is the risk of major damage caused by fires. Therefore, systems that promptly shut off gas supply when a major earthquake occurs to prevent secondary damage are important for improving society's disaster response capabilities.

Tokyo Gas Network (Minato City, Tokyo Prefecture; President Satoru Sawada), which supplies gas to approximately 12 million households in the metropolis and six prefectures of the Tokyo metropolitan area, is responsible for ensuring safety and security during disasters and for early restoration of social infrastructure. The company's 24-hour remote monitoring system, "SUPREME," is said to be an unprecedented real-time earthquake disaster prevention system. We interviewed the company about its earthquake disaster prevention and infrastructure aging countermeasures centered on SUPREME.

"Supply Control Center": The core of earthquake disaster prevention

Tokyo Gas Network was separated and became an independent entity in April 2022, taking over Tokyo Gas's pipeline business in accordance with the legal separation of the pipeline business based on government policy.

Sawada explained, "Our greatest mission is to continue supplying city gas stably 24 hours a day, 365 days a year. We are responsible for regular equipment inspections and maintenance, rapid emergency response in the event of gas leaks, preparation for natural disasters such as earthquakes and early recovery during disasters and realizing comfortable living through the spread of city gas."

To supply gas safely and allow people to use it with peace of mind, the company is focusing on strengthening measures against social issues such as the intensification of natural disasters and aging infrastructure. The core of its earthquake disaster prevention is the "Supply Control Center," which constantly monitors and controls the operating status of city gas production and supply facilities.

The Supply Control Center Is located on a large floor inside the Tokyo Gas headquarters building, which houses various group companies, and serves as the command center for the proprietary earthquake disaster prevention system SUPREME. When we visited the center, the staff members working that day were continuing their monitoring with a sense of tension.

The key to "preventing secondary damage" and "early recovery" is gas pipeline network blocking

The key to "preventing secondary damage" and "early recovery," which are the basics of earthquake countermeasures for city gas, is the blocking of the gas pipeline network. The introduction of blocking began early, dating back to the 1980s before the 1995 Great Hanshin-Awaji Earthquake. The blocking of low-pressure pipeline networks connecting to individual households began after Tokyo Gas became a designated public institution under the national Basic Act on Disaster Management in 1983, and by 1989, the vast supply area was subdivided into 100 blocks.

After the 1995 earthquake, the company expanded and strengthened its earthquake disaster prevention measures. In 2001, it launched the earthquake disaster prevention system SUPREME, and after the Great East Japan Earthquake and Kumamoto Earthquakes, added functions such as liquefaction and flood damage countermeasures.

LNG (liquefied natural gas) imported by tanker is vaporized at LNG terminals, then reduced from high pressure to medium pressure at governor stations and further reduced to low pressure by pressure regulators called district governors. The pipelines that transport this gas are vital lifelines, with a total length of 64,000 kilometers. Ninety percent of these are low-pressure pipes connecting to individual households.

Currently, the low-pressure pipeline network is divided into more than 300 blocks and the medium-pressure pipeline network into more than 25 blocks. In an emergency, only areas (blocks) with significant damage requiring countermeasures have their gas supply stopped, while other areas continue to receive supply. This series of operations is remotely controlled from the Supply Control Center. Shutdown operations that took 40 hours before the system was introduced (because staff had to go to the site) can now be completed in just 10 minutes.

In this system, approximately 4,000 district governors are installed within the gas supply area. Inside them are seismometers called "SI sensors," developed jointly by Tokyo Gas (at that time) and precision instrument companies. These seismometers measure "SI values," which quantify "how much buildings shake due to earthquakes." A seismic intensity of 5 Upper corresponds to SI values of 21-40, and 6 Upper corresponds to 71-120. Information on SI values accompanying earthquake occurrence is transmitted to the Supply Control Center within 5 minutes. Earthquake disaster prevention experts point out that this high-density seismometer network with an average spacing of about 1 kilometer is "unprecedented in the world."

Improved earthquake resistance and aging countermeasures are integrated

An accident in January 2025, in which a road near an intersection in Yashio City, Saitama Prefecture suddenly collapsed, killing a truck driver, was caused by damage to aging sewer pipes. The necessity of countermeasures for aging infrastructure built during the period of high economic growth and exceeding its service life had been pointed out before the accident, and the accident made it an even larger social issue.

According to Director and Senior Managing Executive Officer Tomoo Imai of Tokyo Gas Network, immediately after the first collapse occurred, the company's emergency response vehicles were dispatched and confirmed that there was no gas leak around the sinkhole. Meanwhile, to prevent possible leaks, emergency work to install new valves was carried out to narrow the range where gas would be stopped as much as possible, and supply to 130 households was stopped. A gas pipe detour route was secured for safety, and supply was resumed two and a half days after the accident.

Countermeasures for aging city gas infrastructure are integrated with earthquake disaster prevention measures, centered on strengthening various facilities, including gas pipes. For example, the old low-pressure pipes were "gray cast iron pipes" containing graphite, which could be damaged when strong force was applied. According to Imai, more than 4,000 kilometers of these pipes remained as of 1996, but they have been sequentially replaced with polyethylene pipes that do not corrode and are difficult to break. All gray cast iron pipes are scheduled to be renewed by the end of fiscal 2025.

In addition, welded steel pipes with excellent strength and flexibility are used for high-pressure and medium-pressure pipes; their high earthquake resistance was confirmed in the Great Hanshin-Awaji Earthquake and Great East Japan Earthquake. Spherical gas holders also have earthquake-resistant designs, with vibration damping devices installed. Regarding infrastructure aging countermeasures, Imai says, "the three key points are construction of high-quality pipelines, proper maintenance of facilities, and rapid measures in emergencies."

Gas companies from across Japan came together for early recovery after the Great East Japan Earthquake

During the Tohoku-Pacific Ocean Earthquake that caused the Great East Japan Earthquake, Tokyo Gas's gas supply areas also shook significantly. According to officials, SUPREME operated immediately after the earthquake occurred, and in areas where shaking of seismic intensity 5 or higher was detected, safety devices in gas meters (microcomputer meters) installed in individual households operated to automatically shut off gas supply, ensuring the safety of approximately 3 million households in the target areas.

The author also experienced the rapid gas recovery in Sendai City through post-earthquake coverage. According to Tokyo Gas Network, city gas operators from across Japan, including the Tokyo Gas Group, worked on gas supply recovery in Sendai City and Ishinomaki City in Miyagi Prefecture, Iwaki City in Fukushima Prefecture, and Tsuchiura City in Ibaraki Prefecture. In Sendai City, where gas supply to approximately 360,000 households was stopped, about 50 operators gathered, led by the company, to form a local relief response headquarters, and completely restored gas supply on April 16.

Tokyo Gas Network's Imai explained that the three key points of earthquake disaster prevention basics are "prevention" through earthquake-proofing facilities, "emergency response" through rapid gas supply shutoff targeting appropriate areas using SUPREME, and "recovery" through mutual cooperation among gas operators nationwide.

Strengthening countermeasures through coordination with electricity, communications, and water supply

The Supply Control Center has dedicated terminals and hotlines installed for information sharing with the Cabinet Office and Tokyo Metropolitan Government, building a system to prevent the growth of damage through mutual cooperation. The company also coordinates with Tokyo Electric Power Company, NTT East, and Tokyo Metropolitan Bureau of Waterworks, which are responsible for critical social infrastructure such as electricity, communications, and water supply, strengthening countermeasures while exchanging information.

"Environmental changes such as the intensification of natural disasters and social issues (such as infrastructure aging countermeasures) are becoming apparent. As a city gas operator that continues to deliver city gas to support customers' lives and industrial activities while accurately responding to these issues, we are working day and night to fulfill our mission and responsibilities. We will continue to utilize digital technology and establish a solid business foundation so that city gas will continue to be chosen as an indispensable energy source for the future." Sawada says this while envisioning scenarios including earthquakes directly beneath the capital.

Tokyo Gas Network's promotional video also emphasizes the following: "Our disaster countermeasures have evolved based on lessons from past earthquakes. We must continue to strengthen preparations for earthquakes directly beneath the capital. As protectors of lifelines, we city gas operators will continue visible efforts in invisible places to strengthen earthquake disaster prevention and aging countermeasures. Peace of mind, safety, and trust are our responsibility."

Thoroughly implementing pre-disaster prevention in preparation for earthquakes directly beneath the capital, which are expected to cause massive damage, and maintaining stable supply of city gas, a fundamental energy source, even in emergencies: the efforts of a company operating a highly public business continue.