A Human Disaster
Shirley Dent talks to earthquake expert Andy Thompson.
"Earthquakes are human disasters." Emphatic and unassuming, Andy Thompson of Arup Advanced Technology and a member of the UK Earthquake Engineering Field Investigation Team (EEFIT), working under the auspices of the Institute of Structural Engineering, sweeps away the gambling chips of nature's all powerful casino "earthquakes are natural phenomenon beyond our control" and literally replaces them with the building blocks of science. Seismic structural engineering is a science that allows us to design and build structures that remain standing even when the energy release at the epicentre of an earthquake can be 1000 times more than that of the Hiroshima bomb. The energy released in the Gujarat earthquake was 1000 times that of the Hiroshima bomb (the Gujarat earthquake measured 7.7 MwHRV on the magnitude scale, which is a clearer indicator of damage than the Richter scale). The sharp mind will then decide: but structural engineering obviously failed here the buildings could not withstand that amount of energy released science can only go so far in withstanding natural catastrophe. But the sharper question comes when Andy points out that in a major seismic event in Los Angeles (the 1994 Northridge Earthquake), less than 60 people died in comparison to the devastation of Gujarat, where a 30,000+ lives were lost. 60 lives too many, and 30,000+ lives too many, as Andy quickly points out, but the 500-fold difference in lost lives comes down to one major thing: the non-application compared with the application of scientific principles. In other words, if buildings are built rationally in a high-risk earthquake area, they remain standing. If they are built irrationally, they collapse.
And it is the actual application that is crucial here. As Andy points out, India has a good building code (the current version of the Indian Seismic Design Code, IS1893: 1986 is similar to the American UBC of that time) and some of the finest structural engineers in the world. Yet the buildings in the Gujarat region for several reasons were not constructed using knowledge that has been available since the 1970s.
"We've known since the 1970s how to design for earthquakes. The 1971 San Fernando earthquake in California was a real milestone in earthquake engineering many things were learnt." Yet in the 21st century an earthquake devastated Gujarat. Why?
It is important to realise that the earthquake was not a total apocalypse. Buildings did remain standing even in the epicentral region at Bhuj. The buildings that remained standing were government buildings public utilities and the like that had adhered to the building code, old buildings built in the Raj period with walls up to a metre thick, and belying the fact that money buys safety shanty buildings, which had the flexibility and lightness "just rags" simply to float on top of the ground motion.
Geography had a part to play. Ahmedabad, the capital of Gujarat, was built on thick deposits of alluvium. "Any time you get ground shaking with soft soil, the period content of the ground motion is long the ground goes whoam, whoam, whoam [moving his hand from side-to-side relatively slowly], the taller buildings resonate with the movement and collapse", unless, that is, they are designed and constructed for earthquake forces. This includes no "soft storeys".
This was my first introduction to the demon of those that design for earthquakes: the soft storey. What is a soft storey? A building with a soft storey is a "relatively stiff structure, with a flexible first storey" like a tower block resting on columns to allow cars into the underground car park; that's a soft storey. This poses no problem in the usual course of things, but in earthquake vulnerable areas, these design features cost lives. Andy explained:
"What happens in any seismic event is you're going to get displacement demand on your structure this seismic demand should be distributed evenly over the length of the structure. If, however, it is concentrated at one level if it's quite stiff and then flexible at the bottom, you're going to get all the rotation there". The consequence of soft storeys in Gujarat was that buildings just collapsed at the knees, as if they were made of jelly, whole levels simply disappearing.
Town-planning also had a crucial part to play. In many places the streets were just too narrow for people to escape. Those fleeing were trapped when buildings collapsed into those picturesque alley-ways. Andy's frustration is quietly palpable when he whispers "Anjar was just a mess."
There is a deadly and literal truth when rationalists say that the building blocks of science save lives. In Gujarat, even if buildings had not been constructed or designed strictly within the code, some remained standing because they were built with care from block work rather than rubble construction. The villages that "were shaken to bits" were made from rubble construction "random rubble stones with mud or cement mortar". When the tremor hit they disintegrated.
The phrase "the beauty is in the detail" has life-saving importance in designing buildings to withstand earthquakes. "Detailing is very important". Detailing as Andy describes it has a kind of transcendent finesse; the kind of natural patterning that ensures a spider's web is both flexible and strong. Indeed structural design is no Ozymandias feat of man defying the natural world, but assimilation, an understanding of natural force. As Andy describes, structural engineers harness and channel destructive force:
"When you are designing for life-safety you're usually assuming some degree of damage the key is to put this damage in the right place. Damage can help the designer by limiting the amount of force that the structure attracts. It's like a coat hanger you bend and bend it until you get to a point that it takes a constant force to continue to bend it. At this point, the hanger attracts no additional force. If you get your structure to that level it doesn't attract any more force from the earthquake. The key is you want that damage in very specific spots."
But humanity, as we know, inhabits not just a natural plane, but a cultural and economic one as well. I asked Andy how easy it has been for the EEFIT team to translate what happens when buildings are built in relatively rich California to an area such as Gujarat. The answer was somewhat surprising.
The key, in many ways, is not economic enrichment but scientific simplicity simply applied.
"If you can avoid simple things such as soft storeys, if you can make the building symmetric, if you have good detailing, very simple things like that, all of these would be an immense help it would be huge. You could really save a lot of lives by simply not having soft storeys. That's what we're actually in the process of doing writing simple documentation to making buildings safer."
Andy is fully aware that specialised knowledge alone is not enough to change the landscape of earthquake hit zones. Interpretation is vital. "The engineering community needs to get more involved in the policy of administrative control. This has to happen at a very high level where we can really look at the system. Many buildings were built where the construction and design were poor. Somehow, the builders got through the system and people are now occupying the buildings." "When we were out there we realised that the community wanted not just money, but expertise; they wanted to know how to build correctly. We were driving around and this happened several times we had to ask directions and they would say "where are you from" and we would say "the UK" and they would say "Are you an engineer?" and we would say "Yes" and they say would say "Please, please come to my home and take a look at it, tell me is that okay, tell me how to build it correctly."
"There is a huge awareness and hunger for this knowledge people don't want money without knowing what to do with it."
Andy is part of a growing international community of engineers trying to work with local, national and international governments to ensure that the "lot of talking" that is taking place in the aftermath of the Gujarat earthquake translates into "a lot of action".
When I ask Andy who is going to win: the earthquakes or the engineers, a faint smile hovers over his lips for a moment, shocked that I could ask such a stupid question.
"Oh, the engineers earthquakes are not natural disasters. They are human disasters. We have known how to design for earthquakes for a long, long time."
Andy Thompson is part of the EEFIT team