EASING political tensions in Turkey鈥檚 eastern quake zone, one of the most volatile but least studied parts of the planet, have finally allowed seismologists to investigate the area in detail. The results, which threw up some surprises, should help avoid catastrophes like the deaths of schoolchildren in a quake last May.
Conflict between Kurdish separatists and the Turkish government has made it difficult for earth scientists to get into eastern Turkey since the late 1970s. But by 1999, when a team of geophysicists from several US and Turkish universities were due to start their extensive study, Turkey鈥檚 military had cracked down on the separatists. 鈥淲e hit it at just the right time,鈥� says Eric Sandvol from the University of Missouri-Columbia.
The team distributed 29 seismometers across the three tectonic plates in the area. Over two years they measured 1200 local quakes, plus disturbances from thousands more around the globe, to form a snapshot of the ground beneath a young mountain range being created by the collision of the Eurasian and Arabian plates (see Map).
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Their results, says team member Niyazi Turkelli, reveal hidden fault lines that will help local villagers decide how and where to build vital structures such as hospitals and schools. For example, the team found signs that the northern Anatolian fault 鈥� the one responsible for disastrous quakes in Istanbul 鈥� might stretch much further eastwards than thought, into Iran. That knowledge should help avert incidents such as the collapse of a school dormon dozens of sleeping children during a quake in Bing枚l in May.
Surprisingly, all the quakes the team saw were confined to the top 20 kilometres of crust. That contradicts the previous assumption that much deeper quakes happen in the area, due to one plate thrusting under the other at depth. Instead, Sandvol says, the plates are ramming straight into each other with no under-thrusting at all, so quakes in the area could be stronger on average than thought. 鈥淭here鈥檚 no question that shallow quakes are more destructive,鈥� says Sandvol.
Most surprisingly, measurements of seismic velocities show that the area is one of the hottest bits of crust ever measured. 鈥淚t鈥檚 extremely anomalous,鈥� says Sandvol. At 1200 掳C, eastern Turkey鈥檚 crust seems to be as hot as rift zones 鈥� where plates are pulled apart and deeper molten rocks flow up to fill the gap 鈥� and even 鈥渉ot spots鈥� where columns of molten lava are thought to surge towards the surface from the molten core. Sandvol thinks this is because the floor of an ancient ocean called Neotethys snapped off the Anatolian plate several million years ago and was swallowed up under the Eurasian plate. That melting rock is apparently still belting heat into the crust today.
But science alone won鈥檛 solve Turkey鈥檚 struggle with earthquakes. The Marmara quake of 1999 in western Turkey killed up to 18,000 people even though fault lines in the area were well known. A big part of the problem was simply that many of Turkey鈥檚 buildings are not built to code. 鈥淟ow-quality concrete is the biggest problem,鈥� says Mustafa Erdik from Bogazici University in Istanbul. A recent review of Istanbul showed that up to 50,000 structures need to be torn down or fixed. The city now has a 鈥渕aster plan鈥�, announced last month, to start addressing this.