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Combined Satellite Data Add Up to Clearer Picture of Turkey's SeismicRisks
By Frederic Castel
Special to SPACE.com
posted: 12:34 pm ET
17 March 2000
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gps_sidebar_000315 Satellite imagery is not the only space tool that experts rely upon to help solve the dazzling puzzle of temblors. Over the long term, the Global Positioning System (GPS), in conjunction with laser satellites (Satellite Laser Ranging, or SLR), and linked with small automatic ground-station receivers monitor minute and imperceptible motions of the large and small crustal plates. These plates, ranging from 31 to 62 miles (50 to 100 kilometers) thick, constitute Earth's surface layer. The satellite measurements of plates colliding, diverging and slipping past each other -- called plate tectonics -- give a more complete picture of the seismic regions. In the case of Turkey, three continent-sized plates move across the Earths surface and interact along their boundaries. The earthquakes along the Anatolian fault system that threaten Turkey are generated by the northerly motion of the African and Arabian plates against the Eurasian plate. These quakes result in the deformation in the eastern Mediterranean. But each activates different portions of the Anatolian fault system, directly affecting Turkey's landmass. A team from the Massachusetts Institute of Technology (MIT), in cooperation with universities in Turkey, is using the ground-station receivers associated with GPS and SLR. They have been able to monitor the ground deformation in and around the Sea of Marmara for six years with an incredible accuracy. Robert Reilinger and his MIT colleagues have measured the displacement of two rigid blocks along the North Anatolian fault to find that it moves about 1 inch (2.5 centimeters) per year. In recent years, combining satellite images from Spot, SLR, LandSat and the European Remote Sensing satellite (ERS), scientists have determined the geometry of the Northern Anatolian fault separating the Eurasian and Anatolia/Aegean blocks.
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