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Defying the acts of God

Was the death toll caused by the Turkish earthquake inevitable? asks David Cowlard

The earthquake that shook Turkey on 17 August, killing an estimated 40 000 people, shocked the world. But, says Dr Ray Willeman of the International Seismological Centre in Newbury, it 'wasn't a big surprise' to the experts that such a quake occurred on the North Anatolian Fault. While seismologists may not be able to predict exactly when an earthquake will happen, explains Willeman, they can estimate how much the ground is likely to shake in a particular place - information which engineers and architects can take into account when building. And with the wealth of technology now available to forecast the impact of earthquakes and build structures capable of withstanding them, he says, there was certainly no 'natural' reason why Turkey should have suffered such devastating consequences.

The Turkish earthquake registered between magnitude 7.1 and 7.4 on the Richter scale. A magnitude 4 earthquake 'is equivalent to a 10-kilotonne nuclear explosion', says Willeman, 'and each one-unit increase in magnitude is a factor-30 increase in energy'. But it is more useful to think about acceleration than force. 'Generally when you get up to magnitude 7 the acceleration reaches around 1G. The ground shakes enough to throw something up in the air; that is, the ground has to accelerate away from the object faster than gravity so that the object is left up in the air behind it.' This is measured by strong motion recorders sensitive to high frequencies and designed to record high velocities or accelerations.

Nobody has reliably documented acceleration in excess of 2G; which means that earthquakes of this size are possible, but unlikely. Dr Willeman suggests that building structures capable of withstanding 2G would avoid catastrophe in most cases. 'To make things withstand moderately severe earthquakes of around magnitude 7, you have to withstand 1G - and if you have an ability to withstand 2G of acceleration you are going to ride out almost anything.' He thinks that 'earthquakes of this size shouldn't cause the amount of damage seen in Turkey'.

Given the advances in modern engineering, it is entirely possible to build structures capable of withstanding massive quakes. The Earthquake Engineering Research Centre at Bristol University has one of the most sophisticated testing systems for new structures, materials and components, and provides one of the first stages in testing these under earthquake conditions. The centre uses a shaking table capable of generating powerful 'earthquakes' which then 'shake to destruction' 1/3 or 1/2 scale models of buildings.

Dr Paul Greening, who at the time of writing was preparing to go out to Turkey as part of the Earthquake Field Investigation Team, explained that the work at Bristol is divided into two areas: cutting-edge research into new materials, and the more commercially-orientated work with product testing. Currently a large part of this work involves testing computer racks for telecommunications systems - vital for keeping communications up and running during an earthquake. The process of testing and learning from real earthquakes means that the modern engineering standards and building codes should allow for a dramatic decrease in deaths caused by an earthquake.

Lessons learned from the 1995 earthquake in Kobe, Japan, illustrate how examining each earthquake can lead to further improvements in building and engineering. Dr Greening explains that most of the buildings built to the more recent Japanese codes had fared rather well; but the earthquake caused some unexpected problems. 'The Kobe earthquake had a large vertical component of loading, so there was a lot of up-and-down movement which perhaps hadn't been anticipated. There was also a lot of pounding of one building against another one. There is a phenomenon called the soft storey effect, where the columns in a building change thickness at a certain height because they don't need to carry such a load, and these become a weak point when shaken. In a lot of the photographs you would see that a whole storey of the building would have just pancaked.'

With the advance of technology to cope with earthquakes, there was clearly no need for so many deaths in Turkey. Even in the last decade, other earthquakes of a similar magnitude have had far less catastrophic consequences: the Kobe earthquake killed 5500, while in San Francisco in 1989 only 63 people lost their lives. Natural disaster can be contained - and often is. So what went wrong in Turkey?

The media's attention focused on the corruption of the Turkish system, and the failure of unscrupulous builders. Turkish officials have acknowledged using poor quality materials and mixing concrete with sea sand. But the impact of this earthquake is down to much more than corruption and cost-cutting.

Developed countries like the USA and Japan will always fare better in earthquakes than developing nations such as Turkey, for the simple reason that they have the resources necessary to devote to the research and technology. What tends to be overlooked in discussions bemoaning the corruption of officials or the incompetence of governments is a far more fundamental problem - that however incredible the technological potential to save lives from natural disasters may be, relatively few countries are able to take advantage of it today.

Ironically, at the very time when research and technological developments have reduced the possibility of huge death tolls from earthquakes in developed countries, there is a growing hostility to development itself. The 1990s have been the International Decade for Natural Disaster Reduction (IDNDR), a UNESCO-sponsored programme with an emphasis on the use of awareness campaigns and 'appropriate' technology. But surely what is needed to move countries such as Turkey out of a world that can be reduced to rubble by natural forces is the best possible technology - not what UNESCO officials deem to be appropriate for Turks.

David Cowlard is co-founder of the Urban Research Group

Reproduced from LM issue 124, October 1999



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