Earthqaukes in Japan Part 3

Part 1. Part 2

Architecture verusus Earthquakes.

There is enough I can say about this topic to warrant it's own essay, be that as it may, I will touch on some of the key points here.

It might be alarming to learn that the majority of homes in Japan are only designed to withstand a 7.0 on the Ritcher scale (with apartments and office towers being subject to slightly higher tolerances). This is despite the potential for a much bigger earthquake as we in Japan are waiting for the Big One. It’s important to consider the vast majority of large earthquakes every couple of years are only going to be in the 6.0 to 6.9 range, with thousands of smaller ones every year. A pragmatic analysis concludes all things being equal, there is little benefit of from every structure being able to withstand a 9.0: One, it may never come; two; it would cost a fortune; three, because of several variables, there is no guarantee it could withstand it anyway.

There is one basic element of earthquakes I have not yet discussed, while there are many scientific differences between a 7.0 and a 9.0 earthquake, one is directly applicable to architecture. The movement of the ground is roughly the same for both, however, a 9.0 earthquake can last much longer, with violent shaking occurring on for minutes. This can, in effect, almost liquefy solid ground.

The government has identified certain buildings as vitally important in the event of a large scale earthquake as such police and fire stations are subject to yet more rigorous standards. Also, some public buildings have been designated as emergency shelters after an earthquake, these include schools and public facilities (such as the Chomin Hall where I work). After the big one, it is expected that these buildings will still be standing.

How does this affect the architecture? This is what I am primarily interested in. In designing a structure to withstand an earthquake greater than 7.0 one needs either great strength or flexibility. In most modern examples, many gigantic reinforced concrete pillars are used, and to great visual effect I think. This is still not a perfect solution because the possibility exists during the Big One of the earth opening up and swallowing a structure.

A structure designed to these increased standards are easy to spot because they share a couple of common characteristics. More often then not, visually the buildings look low and strong. One can easily see the pattern of exposed concrete or, if covered, a careful eye can identify the support system. Personally I like unfinished concrete but I can understand how one might find it cold. I think a lot has to do with the amount of natural light in the structure, the partnering materials (such as wood) and in-floor radiant heating (if the feet feel warm the body feels warm). Metaphorically, the buildings look like they are resisting a great force from above, like a giant hand pressing down on it. But unlike the grey sagging facade of a large discount store, here the structure is pressing back—straining—but defiant. Overall, the impression is bold and expressive.

[Image: Above and to the left, one can see a small side entrance to Chomin Hall. Note the large lintel pattern etched in the concrete above the doorway to visually reinforce the strength and weight of the structure bending around the door. Directly below is an image of a reinforced concrete wall in Chomin Hall. Good lighting, so it doesn’t feel like a basement, is used in Chomin Hall. The last image is a wide angle shot of Shikaoi’s fire station. I think with careful study the reader can identify the characteristics I have discussed above. Sorry about the snow.]



I would like to end on quick note about how ancient Japan dealt with building in a seismically active zone. Studying this topic in depth, I am always surprised that without modern scientific knowledge the Japanese discovered the perfect combination of materials and construction techniques to build effective earthquake-resistant structures and they happen to be the same techniques we use today. For example, Nara’s Horyu Temple is home to the worlds old wooden structure; a thousand year old pagoda. In modern times we have use a brute strength approach toward building earthquake-resistant structures, however, ancient Japanese builders harnessed flexibility. (Modern skyscrapers still employ this method). Wood is a great material to build with in an earthquake prone area because it is strong, light, and flexible. Next is a material not so much they did, but didn’t, use—nails. They were invented, of course, but if used in this manner nails would have made joints far too ridge in the event of an earthquake. A natural, effortless flexibility between post and joint is desired. Design was important too because careful planning could control the total amount of flexibility. Too little flex and the structure was at risk of being torn from its foundation and collapsing in an earthquake, too much flex and the structure was at risk for moving passed its center of gravity and toppling over. (Again, much the same problem is faced in modern skyscraper design but the Japanese did it without the help of computer models.)