Panel A

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Figures from McClusky et at, discussion by Stein & Wysession

A complicated situation occurs in the eastern Mediterranean collision zone involving the African, Arabian, and Eurasian plates (panel c) Combining the motion of GPS sites in the western Mediterranean relative to Eurasia (panel a) and focal mechanism data (panel b) shows the complex motions. Western Turkey and the Aegean Sea rotate as the Anatolian plate about a pole near the Sinai peninsula. Anatolia is thus "squeezed" westward between Eurasia and the northward-moving Arabia, like a melon seed squeezed between a thumb and forefinger. The motion across the North Anatolian fault, about 25 mm/yr, gives rise to large right-lateral strike-slip earthquakes such as the 1999 M 7.4 Izmit earthquake, which occurred about 100 km east of Istanbul and caused more than 30,000 deaths. To the west, the data show interesting deviations from a rigid Anatolian plate. The increasing velocities toward the Hellenic arc, where the Africa plate subducts below Crete and Greece, show that western Anatolia and the Aegean region are under extension, consistent with the normal fault mechanisms like that of the February 4, 2002 earthquake. This region may be being "pulled" toward the arc, perhaps by an extensional process similar to oceanic back-arc spreading. In contrast, eastern Turkey is being driven northward into Eurasia, causing compression that appears as the thrust fault earthquakes in the Caucasus mountains.

McClusky, S., and others, Global Positioning System constraints on plate kinematics and dynamics in the eastern Mediterranean and Caucasus, J. Geophys. Res., 105, 5695-5719, 2002.

Panel B