Things to learn from the Great Hanshin Earthquake

--- Current anti-earthquake measures were based upon the Great Kanto Earthquake, but what should be considered in the wake of the most recent trembler?

Kobori: This type of terrestrial earthquake occurs only once in several hundred years. The lessons we can learn from this type of underfoot trembler consequently lean towards countermeasures. The type of earthquakes that strikes such areas as Tokyo and Nagoya tend to have their epicenters in deep locations off-shore and are of greater magnitude. This, of course, leads to different earth movement. The extent of the damage in the most recent quake was magnified by the fact that a quake of this size was not expected in the area it struck. However, Kajima-built structures, designed with technology which conforms to the new anti-quake standards, received surprisingly little damage. Although it is important to learn from the destruction, it is even more important to discover why certain structures escaped damage to improve levels of safety. Up until now we have concentrated our efforts on primary destruction, or the safety of buildings affected directly by the earthquake, but secondary destruction is continuing even now. I believe that we must consider this also.

Kojima: I feel more and more that a stable structure alone is no longer sufficient. Emergency power and emergency elevator operations were put on line too late after the quake struck. I was of the opinion that auxiliary generators to provide emergency power should have kicked in within 40 seconds of the electricity being cut, but this was not the case. Even when generators did work, severed water supplies prevented water cooling which led to overheating and subsequent power cuts. The fact that emergency elevators needed to reach various levels in a building rely on these generators for power was especially conspicuous intheir failure to be of any use. All consequent efforts to review anti-earthquake measures for highly-concentrated residential structures must also take internal facilities into account, as regardless of how stable the building may be, damage to internal utilities can cause unbearable suffering for the residents. We were always of the opinion that safety was commiserate with a stable structure, but we now know that this alone is insufficient in reality. I believe that it is necessary in the future to include not only building configuration into anti-quake designs, but also fixtures and fittings. I also think we should discuss exactly what the area and city ought to be like in our plans for revival. Orders for building construction and internal facilities have recently been separated, but I think this raises queries in light of the recent quake. I feel that this can be solved by unifying all general contractors and taking the initiative with regards to planning, construction and facilities.

Kobori: Yes, we have to do away with the practice of breaking work down into defensive barriers, as has been the case up until now. For example, there were situations where there was nothing wrong structurally with a building, but the elevators did not work and the internal fittings were in a terriblemess. However, if sway is decreased through tremor control and tremor absorption, this will become a thing of the past. One year ago during the Northridge earthquake there was a hospital which was unaffected structurally, but lost all of its functions. The strong tremor knocked all medicine from the shelves, triggered the sprinklers and soaked all medical charts with water. This most recent quake inflicted severe damage on nearly 90% of hospitals. The hospitals were unable to function in the immediate aftermath of the earthquake when they were most needed. It will be impossible to guarantee safety during earthquakes if we do not exceed the framework of these defensive barriers and operate within the true meaning ofgeneral contractors.

--- And how did civil engineering structures fare?

Nojiri: It is thought that the biggest problem was the fact that most of the roadways, or so-called lifeline, were rendered unusable. Although there were obvious planning problems, the fundamental problem was three-dimensional use of space representative of the expressways. I mean that the structures should be viewed three-dimensionally and not individually. Constructions are individual, but roadways and railways are continual lines, and the fact that a severance in one point can disfunctionalize the entire line is their achilles heel. Design was not carried out three-dimensionally. The result of this is that areas in which stress is most apparent and areas which are subject to damage crumbled. Another point here is the fact that roads situated beneath overhead roadways become unusable when the upper structures are damaged, and this produces obstacles for relief activities. I am sure that this point has been discussed more than anyother in the aftermath of the quake. The failure to maintain any form of back-up system also revealed a weakness in Japan's social framework. The major cities in Europe and America are linked by a series of bypasses. I feel that the greatest lesson we can learn from this disaster is our failure to provide three-dimensional anti-quake designs which takes into consideration seismic plates and ground formation.

Kojima: The ground formation of Kobe runs in a long-thin line from east to west, and all of the so-called 'lifeline' facilities are concentrated within it. When the lifeline is unusable, the only method of access is by air or sea. Incidently, the port facilities also received a devastating impact.

Damage occurred to the railway lines, or so-called 'lifeline', in several areas

Nojiri: Anti-earthquake sea walls have recently been built, and the port of Kobe is equipped with these in several places. Despite the enormity of the quake, these walls received very little damage. I would say that we need to review the port facilities as another part of the lifeline.

HOME back index
All Right Reserved,Copyright(c)Kajima Corporation 1995