Like California, Japan and other temblor hot spots around the globe, Turkey's earthquake risk is high because it's a site where plates, or blocks, of Earth's crust converge.
In Turkey, the Eurasian and Anatolian/Aegean plates meet. They overlapped during the 1999 quakes along a distance of 68 miles (110 kilometers). Satellite imagery is the most effective method of revealing such data.
Overall, the surface of the Earth is divided into a dozen or so large plates near the surface, and several smaller ones. As these plates move in relation to one another, stress and strain builds up in the rock. When the strain reaches a certain point, the rocks snap, and the ground moves.
Sometimes, though, the ground slips over time. Along the Anatolian Fault, as well as the San Andreas Fault in California, this process, called slippage, can crack sidewalks and move buildings in a slow creep lasting many years.
At present, the average rate of slippage along the main fault that ruptured in the area of Golcuk, Turkey, last August is about 0.8 inch (2 centimeters) a year.
Satellites can be used to precisely measure this slippage, knowledge that researchers use to help understand the overall stress building up along a fault. From space, a series of camera views can examine the gigantic rupture that occurred last August along the North Anatolian Fault in Turkey.
"With an average 250-year natural recurrence between two earthquakes [on the same fault segment], the fault builds up a potential 5-meter (16.4-foot) slip that will be suddenly released when the quake happens," said Bertrand Meyer, a researcher with the Paris-based Institut de Physique du Globe de Paris.
"Over the last 60 years, earthquakes, including the latest events, have ruptured successive segments on a 1000-kilometer (620-mile) long portion of the fault -- a little bit like a zipper running westbound. Unruptured segments extending westward under the Sea of Marmara, south of Istanbul, remain loaded and are likely locations for the occurrence of future earthquakes," Meyer said.
But satellite imagery just provides clues to the seismic threats in the region.
"Even if prediction of earthquakes was possible, it wouldn't prevent dangerously built houses and buildings from collapsing and killing people," Meyer said.
"The only way to create efficient prevention is to determine good anti-seismic standards. Such an objective requires a good knowledge of the active faults and the evolution of their network."
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