98% of Turks live in `high risk' zone

Criss-crossed with fault lines and wedged between three large, constantly moving tectonic plates, Turkey and the wider eastern…

Criss-crossed with fault lines and wedged between three large, constantly moving tectonic plates, Turkey and the wider eastern Mediterranean region is one of the world's most earthquake-prone zones.

Tremors in the region are quite common, but in the past week Turkey has been devastated by a quake measuring 7.4 on the Richter scale, with at least 2,400 people killed, Iran suffered a tremor measuring 5.1 and the island of Cyprus was rocked by a jolt hitting 5.8 on the same scale.

Coincidence? Very likely, geologists say.

Theories abound that tremors on one fault line could trigger a larger quake elsewhere. Another school of thought says shock waves are absorbed in the earth before they reach another fault.

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Turkey, sitting on several fault lines, is subject to frequent earthquakes and tremors. Some 96 per cent of the country lies in a "high risk" area and 98 per cent of the population lives in this area, according to Ankara's Housing Ministry. Though earth movements cannot be predicted, scientists point to a wave of seismic activity, or an "earthquake storm", in the region which then tends to go quiet for about 35 to 50 years. No earthquakes on a tectonic boundary line for long periods is a matter for concern because mounting stress on a fault line will probably eventually be released in one large quake, they say.

"A number of lines of crust weakness converge in this particular area," said Dr Iain Stewart, a lecturer in earth sciences at the British University of Brunel. The African plate to the south and the Arabian plate to the east are moving north against the Eurasian plate, which moves south, resulting in an accumulation of pressure on the boundaries.

That movement triggered off Tuesday's massive upheaval on the North Anatolian Fault, which starts in Greece and ends in eastern Turkey. "The tremor may be a local phenomenon in the area, but for its preparation the distortion of plates on a much wider scale was responsible," said Seismology Professor George Karaisis of the Aristotelion University of Salonika.

Scientists say the plates move relative to one another at speeds ranging from one to 20 centimetres a year. Large tremors usually occur at the edges of these tectonic plates. "Africa for example has very few earthquakes and the only place where they occur is on the edges of this block. Its northern edge runs right along the Mediterranean, so all of that area is extremely earthquake-prone," Dr Stewart said .

Prof Karaisis and Dr Stewart said there was a remote possibility that tremors in one part of the region could spark a larger one in an area which was already rumbling from accumulated pressure.