[Special Feature: Thinking About Disaster Prevention] Earthquake Preparedness at Keio University: Focusing on Hardware-Side Responses

2018/03/01

"Disaster prevention" is a concept that covers an extremely wide range, including not only preventing disasters and suppressing or mitigating damage, but also emergency response and recovery efforts after a disaster occurs, as well as subsequent reconstruction, crisis management, and BCP (Business Continuity Planning). Here, among Keio University's disaster prevention initiatives, we will focus on "earthquakes," which are the disasters most likely to cause the greatest damage, and explain hardware-side initiatives such as facilities and equipment in each phase of disaster prevention.

With current science and technology, it is impossible to prevent the occurrence of earthquakes, and the level of prediction is not yet at a stage where practical effectiveness can be expected.

For this reason, initiatives to suppress and mitigate damage when a major earthquake occurs become realistic measures. In terms of hardware, this means ensuring that buildings can withstand major earthquakes. In Japan, buildings are constructed in accordance with the Building Standards Act; by complying with this act, buildings meet the established seismic standards and obtain the necessary seismic resistance.

However, seismic standards are frequently reviewed. The seismic standards revised in 1981, the so-called "New Seismic Design Standards," were set to prevent damage from earthquakes with a seismic intensity of upper 5, whereas the previous standards (Old Seismic Design Standards) were different. The new standards are designed to provide structural strength so that buildings may be damaged but will not collapse or crumble during earthquakes with a seismic intensity of upper 6 to 7. Consequently, the degree of damage from major earthquakes differs significantly between buildings built before and after these new standards. In fact, during the 1995 Great Hanshin-Awaji Earthquake, buildings constructed under the new standards suffered almost no major damage, while many buildings built under the old standards suffered devastating damage, including collapse.

In the years following the Great Hanshin-Awaji Earthquake, the Juku conducted seismic diagnoses on nearly 100 of its buildings that had been constructed under the old seismic standards. A seismic diagnosis examines whether the structure of a building possesses seismic performance equivalent to buildings designed under the new standards. It is evaluated using several indicators, the most straightforward of which is the Is value (Seismic Index of Structure: calculated for each floor of a building, taking into account the building's strength and toughness against seismic force). If this Is value is 0.6 or higher, the building is considered to have seismic performance equivalent to a building constructed under the new standards (the Ministry of Education, Culture, Sports, Science and Technology has set the seismic performance standard for school buildings slightly higher, at 0.7, rather than the minimum Is value of 0.6).

Based on the results of the seismic diagnoses, the Juku prioritized buildings judged to need reinforcement—such as those with an Is value below 0.6—based on factors like seismic resistance and the age group of the facility users, and formulated a seismic reinforcement implementation plan. In accordance with this plan, seismic reinforcement work has been carried out sequentially since 2003. By 2013, reinforcement work had been completed on more than 30 buildings, and reinforcement is now almost complete for all buildings originally diagnosed as needing it.

As the next stage, we are currently proceeding with seismic diagnoses and reinforcement for small-scale buildings that were not initially diagnosed. Furthermore, for the Old University Library in Mita, which requires the preservation of its exterior design as an Important Cultural Property, standard seismic reinforcement methods cannot be used. Therefore, we are undertaking the difficult task of ensuring seismic performance through the seismic isolation retrofit method (a method of converting an existing building into a seismic isolation structure), which is scheduled for completion in the spring of 2019. Through these efforts, as of the spring of 2018, the ratio of seismically reinforced buildings to the total buildings owned by the Juku has reached 98.4% by floor area.

Furthermore, earthquake damage is caused not only by the collapse or damage of building structures but also by the peeling or falling of non-structural components such as ceiling materials, exterior materials, and equipment. Promoting the seismic resistance of these non-structural components is a challenge for the future.

In the event of a major earthquake, an emergency response to the damage caused is necessary. In terms of hardware, it is important to make accurate judgments regarding the safety of buildings after a disaster. We must prevent secondary disasters by conducting so-called emergency risk assessments to determine if buildings damaged by the earthquake are safe and can withstand aftershocks, and by prohibiting entry to buildings where safety cannot be guaranteed. Architectural engineers from the facilities department who hold qualifications as emergency risk assessors respond to this by inspecting each building, confirming the damage status, and verifying safety.

Additionally, an organization must restore functions degraded by a disaster as quickly as possible. While this relates to crisis management and BCP, the hardware-side challenge is how to support this from a facility perspective. As mentioned earlier, the current Building Standards Act requires a minimum level of seismic resistance that prevents collapse during a major earthquake. However, considering economic factors—such as how much seismic resistance should be required for a major earthquake that may occur only once in a building's lifespan—the approach taken is that for extremely rare large-scale earthquakes of seismic intensity upper 6 to 7, the building will not collapse, though some degree of damage is unavoidable. If damage necessitates rebuilding or major repairs, that building cannot be used immediately.

However, for buildings that serve as bases during disasters, it is not enough that they simply do not collapse; they must function immediately after a major earthquake, and they are required to be buildings equipped with the seismic performance and facilities to make that possible. We must also assume that external supplies of electricity, gas, and water will be cut off. Generally, the amount of food and drinking water stockpiled and the specifications of equipment are assumed to cover three days after a disaster. In reality, there are many elements that need to be considered, such as the assumed number of personnel for calculating stockpile amounts and the scope of power backup during outages. We recognize how to technically achieve this as a challenge for the future.

So far, I have described initiatives regarding the hardware side of earthquake measures, but disaster prevention is more effective when the two wheels of hardware and software are firmly engaged. Improving the organization, systems, and regulations for disaster prevention, as well as raising the awareness of faculty, staff, and students regarding disaster prevention and crisis response, is extremely important for preventing disasters and suppressing or mitigating damage when they occur. We believe it is important that the hardware improvements mainly handled by our Office of Facilities and Property Management are not carried out in isolation, but are advanced while remaining conscious of and coordinating with software-side improvements.

*Affiliations and titles are those at the time of publication.