Global Positioning System Measurements of Crustal Deformation in Azerbaijan

GPS observations in Azerbaijan and surrounding areas are providing quantitative constraints of the geometry of active fault systems, and rates of present-day deformation. West of 48° E longitude, the Main Caucasus Trust Fault (MCT) follows the sharp change in slope along the south side of the Greater Caucasus as is well known from prior geophysical and geologic studies. However, east of this longitude the MCT turns sharply to the south, crossing the Kura Depression and extending along the western side of the Caspian Sea (West Caspian Fault; WCF). While the MCT is predominantly a thrust fault west of 48°E longitude, the WCF is a pure right-lateral, strike slip fault with a slip rate of 11 ± 1 mm/yr south of the Absheron Peninsula. The rate of convergence on the MCT decreases from east to west from 10 ± 1 mm/yr at 48° E longitude to 4 ± 1 mm/yr. The present-day pattern of horizontal motions in aggregate suggests that the Lesser Caucasus and Kura Depression are rotating coherently in a counterclockwise sense about a pole located near the NE corner of the Black Sea, resulting in the observed W to E increase in the rate of convergence along the MCT.