When a natural disaster disrupts the lifeline services of water, electricity, gas, or telecommunications, this can wreak havoc on people’s lives. In order to build resilient lifelines, it is essential to analyze the impacts disasters may have, for example, on underground pipelines, and make use of this information in future designs. Professor KUWATA Yasuko at the Graduate School of Engineering is an expert in lifeline earthquake engineering and, in addition to the importance of strengthening facilities, she points out the need for taking measures based on the assumption that there will be potential damage in the event of a disaster, and for raising awareness among the public.
People recognized the importance of lifelines with the Great Hanshin-Awaji Earthquake
What does lifeline earthquake engineering encompass as a discipline?
Kuwata:
In Japan, the Great Kanto Earthquake of 1923 resulted in amendments being made to the “Urban building act,” and the first-ever standards for earthquake-resistant designs were established in 1924. New laws and standards have been created with each major earthquake ever since.
With lifeline utilities, design methods were established when seismic designs, that is, the design of infrastructure to be resistant to seismic events, were required for laying the underground oil pipelines during the construction of Narita International Airport in the 1970s. As lifelines such as water, gas, or electricity in the buried pipelines are public utilities, the recognition then spread that we should consider not only the design of hard infrastructures, but also the safety of the entire system as a network. This is how the discipline of lifeline earthquake engineering has developed over the years.
I think the term “lifeline” became recognized among the general public in Japan with the Great Hanshin-Awaji Earthquake in 1995. After experiencing the earthquake as a third-year high school student at my parents’ house in Kyoto, I went on to study civil engineering at Kobe University’s Faculty of Engineering, and developed a particular interest for lifelines. As I watched the city of Kobe being rebuilt after the devastation of the earthquake, I wanted to be involved in research related to earthquake resistance.
What kind of impact did the Great Hanshin-Awaji Earthquake have on lifeline earthquake engineering?
Kuwata:
The Great Hanshin-Awaji Earthquake was the first major earthquake to strike an urbanized area which had an extensive network of lifeline pipelines. The fact that the earthquake had damaged not only the lifeline utilities of water, electricity, and gas, but also other infrastructures such as roads and railways resulted in significant revisions being made to seismic designs in civil engineering structures. A recommendation by the Japan Society of Civil Engineers led to creating the categories of “Level 1 earthquake ground motions,” which refer to earthquakes that could occur maybe once or twice during the service period of a structure, and “Level 2 earthquake ground motions,” which are earthquakes that have a larger intensity but lower probability of occurring during the service period. Standards and guidelines were then revised so that structures would be designed to meet the required performance for “Level 2 earthquake ground motions,” according to the importance of the structure.
Before the guidelines were revised, for example, water pipes were designed with the idea of making sure the stress on the pipeline and displacement at the joints did not exceed the allowable values. But after the revision, the focus was placed on the performance of the entire system, considering aspects such as how long the water supply could potentially be cut off as a network, or how many days would be required to have it restored. The revision of the guidelines introduced the idea of performance design.
In lifeline earthquake engineering, more studies now involve the spatial analysis of damage caused by earthquakes, mapping out the specific impacts the ground motion had on underground pipelines, and I am also engaged in such research. Since the Great Hanshin-Awaji Earthquake, Japan has seen many major earthquakes all over the country and the damage to the lifelines has differed in each case. So the results of these analyses have also led to changes in recovery processes and precautionary measures.
Strengthening lifelines costs money, and this is reflected in prices
From the perspective of lifeline earthquake engineering, what do you feel are the challenges of disaster management and mitigation?
Kuwata:
The Great East Japan Earthquake served as a stark reminder of the difficulty in preventing damage from occurring. If the external forces caused by an earthquake are large, damage is inevitable. Of course, we need to avoid situations where the water supply is disrupted for several months after an earthquake, but in many cases, the reality is that people will have to cope without running water for a week or two.
I believe it is important for lifeline providers to inform the public of the actual state of their infrastructure. Instead of simply emphasizing the areas that they have managed to bolster, they should also share information about the areas that they have been unable to strengthen, and how those areas may suffer damage in the event of a disaster. I believe it is also necessary for the general public to accept these realities and make their preparations accordingly. In other words, I believe society needs to be able to accept that there will be damage. If a community is unable to strengthen its hard infrastructures sufficiently before a potential disaster and expects delays in restoring lifelines in the aftermath, it is also important to make preparations such as procuring water trucks in advance.
Regarding the strengthening of water utilities, the reality is that a significant number of municipalities have yet to make their facilities earthquake-resistant. This means we also need to take into account that renovations require large sums of money. We need to recognize that seeking safety and security leads to higher costs, and that this will be reflected in prices. So I feel that societal acceptance is important in this aspect also.
After the 2024 Noto Peninsula Earthquake, you visited the disaster areas to study the damage to the water utilities and how they were being restored.
Kuwata:
With the Noto Peninsula Earthquake, efforts to restore water and sewage services in disaster areas were slow, and more than 50% of households were without running water even two months after the earthquake. The main reason for this was that the water purification plants and water distribution reservoirs, as well as the transmission pipelines had been damaged, and they took time to be restored.
There had been calls for operators to make the facilities earthquake resistant before the Noto Peninsula Earthquake, but the single pipeline system made it difficult to update the main pipeline, resulting in very little actual progress made in earthquake-proofing their facilities.
In recovery efforts, what we now need to consider is whether or not the facilities and pipelines should be restored to their original state. In the past, infrastructures would be restored with the same routes and same pipe material with the same diameter and earthquake-resistance. But as depopulation progresses and communities shrink even further, I believe it may be necessary to perhaps change the way we operate, reducing the size of the water supply facilities and shortening the pipelines. As the population continues to decline all over the country, I also feel that we need to create new models based on the concept of compact cities.
Also conducting research leveraging the fiber optic cables along highways
What are the challenges in your current research?
Kuwata:
One of the changes in recent years is that geological information is now provided as open data after the stronger demand for disaster management and mitigation measures. Meanwhile, it has become difficult to obtain information related to lifeline services. For example, information regarding earthquake damage used to be released to the public in the past, but more municipalities are now choosing not to disclose the information, citing safety reasons and the protection of personal information. I do feel that this is becoming a challenge in my research.
On the other hand, there has been progress with the development of new research methods. For example, fiber optic cables are laid beneath national highways throughout the country for road management and other purposes, but people have begun to utilize them as sensors to monitor seismic activity. This is an extremely efficient method for collecting data, compared to the conventional approach of installing numerous seismometers, as dynamic strain data can be collected from any point along the road by measuring the expansion or contraction of the existing fiber optic cables. We believe that analyzing this data can contribute to the design of underground pipelines. As a first step, we are analyzing the data collected along National Route 9 in Kyoto Prefecture. We have also started measuring data along National Route 43 in Kobe City, beginning in January 2024.
Tell us about the direction and goals of your research in the future.
Kuwata:
Many researchers were interested in the field of lifeline earthquake engineering immediately after the Great Hanshin-Awaji Earthquake; however, the number of engineers and researchers has decreased over the past 30 years. This may be because the era of developing, researching, and improving earthquake-resistant technologies has come to an end, and we have transitioned to an era of maintenance and management. However, the improvement phase is not completely over, and there is still a lot of room for research on earthquake-resistant technologies.
My research so far has been focused more on soft countermeasures, such as building backup systems in preparation of disasters, or planning measures so that communities can get back on their feet quickly after a disaster. But in future, I plan to further my studies into hard infrastructures. By performing experiments on the interaction between the ground and buried pipes, and conducting research and analyses using the fiber optic cables mentioned earlier, I hope to be able to propose performance designs that address the local hazards, ground characteristics, and pipeline network conditions of each region. Ultimately, I hope my research can help strengthen lifelines in both hard and soft infrastructures.
Resume
Graduated from Kobe University Faculty of Engineering in 1999, and received a Ph.D. in engineering from Kobe University Graduate School of Science and Technology in 2004. Became a research assistant in 2004 and an associate professor in 2006 at Kobe University Faculty of Engineering, before becoming an associate professor and then a professor in 2023 at Kobe University Graduate School of Engineering.
