Published online 12 March 2010 | Nature | doi:10.1038/news.2010.121

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Clock ticking for an Istanbul earthquake

A wake-up call for seismic-hazard preparedness in Turkey.

Villagers search among the ruins in Okcular village in the eastern province of Elazig, on March 9, 2010, a day after a strong earthquake.The earthquake that hit Turkey on 8 March has triggered concerns that a quake might strike Istanbul.STR/AFP/Getty Images

The magnitude-6.1 earthquake that hit eastern Turkey at 2:32 GMT on 8 March has provoked fresh concerns over whether Istanbul could be the next Turkish site to be hit by a major tremor — and whether it is adequately prepared should a quake strike.

According to data from the US Geological Survey, the epicentre of the recent quake was 70 kilometres from the city of Elaziğ and about 625 kilometres east of Turkey's capital, Ankara. The earthquake toppled buildings and flattened homes, injuring at least 100 people and killing 41.

Turkey is criss-crossed by faults, produced by the African plate pressing into the Anatolian block. Most of the country is being pushed and squeezed to the west between the North and East Anatolian faults. The Elaziğ earthquake is thought to have occurred on the East Anatolian fault.

The chances that the recent quake could itself trigger a tremor in Istanbul are slim, says Ian Main, a seismologist at the University of Edinburgh, UK: "The stress changes at these distances are too small to expect a significant triggering effect."

Nonetheless, the sprawling metropolis of Istanbul, with nearly 13 million inhabitants, has not been hit by a major quake since 1766. A series of strong earthquakes has been progressing westwards along the North Anatolian fault — most recently at Izmit in 1999 — prompting scientists to worry that Istanbul is next in line.

Click for a larger version of this image.

According to Tom Parsons, a geophysicist with the USGS Earthquake Hazards Program in Menlo Park, California, there is a 30–60% chance of a magnitude 7 or greater quake close to Istanbul in the next 25 years.

Tobias Hergert of Karlsruhe University, Germany, and Oliver Heidbach of the GFZ German Research Centre for Geosciences in Potsdam, also in Germany, published a study earlier this year1 suggesting that the strain accumulating along the North Anatolian fault might be released during several earthquakes rather than in one large rupture of the whole seismic gap. But they add that Istanbul is still at risk of a magnitude 7 or greater earthquake, depending on which fault segment ruptures.

Enormous task

The 1999 Izmit earthquake was a stark reminder for the authorities in Istanbul of the need to prepare their city. Little had been done before that date to mitigate the effects of a potential tremor.

Since then, Istanbul's Metropolitan Municipality has commissioned an earthquake master plan for the city, known as the ISMEP (Istanbul Seismic Risk Mitigation and Emergency Preparedness Project). The project's main goals are to improve emergency preparedness, reduce the risk to existing public facilities and enforce building codes.

Just over ten years on from the Izmit quake, Istanbul is now better prepared and has a better-informed population than many other cities in the world, says Parsons.

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For example, the new terminal at Istanbul's Sabiha Gökçen International airport is designed to withstand earthquakes of up to magnitude 8 and is said by its developers to be the world's largest seismically-isolated building. The local population has been educated through specially designed earthquake-awareness days, including the use of earthquake-simulator machines and emergency drills for school children. Mustafa Erdik, director of the Kandilli Observatory, says that since 1999, earthquake-code compliance has been much better and that there is a "sizeable effort to strengthen schools and hospitals against earthquakes".

But despite these positive steps, the city is becoming increasingly vulnerable to earthquake damage, and the enormity of the task facing the authorities is overwhelming. According to a paper in the journal Natural Hazards2, Istanbul's overcrowding, faulty land-use planning and construction, inadequate infrastructure and services, and environmental degradation are all contributing to the problem.

Meanwhile, the latest earthquake has exposed Turkey's failure to construct sturdy homes in rural areas. Despite renewed attention falling on Istanbul in the wake of the Haiti and Chile earthquakes, the effects of the rupture in the East Anatolian fault show just how poorly prepared the rest of the country is for seismic hazards.

"With media attention and scientific focus currently on Istanbul, it tends to impress on everyone the notion that all is well everywhere else," says Polat Gülkan of the Middle East Technical University in Ankara, who warned of the risks to other regions of Turkey at a recent parliamentary hearing in Ankara on 24 February. "In this country, earthquake potential lurks in virtually every corner." 

  • References

    1. Hergert, T. & Heidbach, O. Nature Geosci. 3, 132-135 (2010). | Article | ChemPort |
    2. Erdik, M. & Durukal, E. Nat. Hazards 44, 181-197 (2008). | Article
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