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Coskun Demir

Bio: Coskun Demir is an academic researcher. The author has contributed to research in topics: North Anatolian Fault & Eurasian Plate. The author has an hindex of 3, co-authored 3 publications receiving 1954 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, the authors present and interpret GPS measurements of crustal motions for the period 1988-1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of Africa.
Abstract: We present and interpret Global Positioning System (GPS) measurements of crustal motions for the period 1988–1997 at 189 sites extending east-west from the Caucasus mountains to the Adriatic Sea and north-south from the southern edge of the Eurasian plate to the northern edge of the African plate. Sites on the northern Arabian platform move 18±2 mm/yr at N25°±5°W relative to Eurasia, less than the NUVEL-1A circuit closure rate (25±1 mm/yr at N21°±7°W). Preliminary motion estimates (1994–1997) for stations located in Egypt on the northeastern part of Africa show northward motion at 5–6±2 mm/yr, also slower than NUVEL-IA estimates (10±1 mm/yr at N2°±4°E). Eastern Turkey is characterized by distributed deformation, while central Turkey is characterized by coherent plate motion (internal deformation of <2 mm/yr) involving westward displacement and counterclockwise rotation of the Anatolian plate. The Anatolian plate is de-coupled from Eurasia along the right-lateral, strike-slip North Anatolian fault (NAF). We derive a best fitting Euler vector for Anatolia-Eurasia motion of 30.7°± 0.8°N, 32.6°± 0.4°E, 1.2°±0.1°/Myr. The Euler vector gives an upper bound for NAF slip rate of 24±1 mm/yr. We determine a preliminary GPS Arabia-Anatolia Euler vector of 32.9°±1.2°N, 40.3°±1.1°E, 0.8°±0.2°/Myr and an upper bound on left-lateral slip on the East Anatolian fault (EAF) of 9±1 mm/yr. The central and southern Aegean is characterized by coherent motion (internal deformation of <2 mm/yr) toward the SW at 30±1 mm/yr relative to Eurasia. Stations in the SE Aegean deviate significantly from the overall motion of the southern Aegean, showing increasing velocities toward the trench and reaching 10±1 mm/yr relative to the southern Aegean as a whole.

1,871 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used displacements of 50 Global Positioning System (GPS) sites together with interferometric synthetic aperture radar (InSAR) range-change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture.
Abstract: Only 87 days after the Mw 7.5, 17 August 1999 Izmit earthquake, the Duzce earthquake ruptured a ca. 40-km-long adjoining strand of the North Anatolian fault (NAF) system to the east. We used displacements of 50 Global Positioning System (GPS) sites together with interferometric synthetic aperture radar (InSAR) range-change data spanning the event to estimate the geometry and slip distribution of the coseismic rupture. Postseismic deformation transients from the Duzce earth- quake and the preceding I zmit event that are included in some of the measurements are corrected for using dislocation models fit to GPS data spanning the various time periods. Nonlinear inversions for fault geometry indicate that the rupture occurred on a ca. 54� north-dipping oblique normal, right-lateral fault. Distributed-slip inver- sions indicate maximum strike slip near the center of the Duzce fault close to the earthquake hypocenter. Slip magnitude and depth of faulting decrease to the west and east of the hypocenter. Both GPS and InSAR data suggest that normal slip is restricted to the shallow portion of the rupture. The Duzce earthquake had the highest slip-to-rupture-length ratio of any historic earthquake along the NAF.

144 citations

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated Global Positioning System (GPS) measurements performed from 1992 to 1999, up to the 17 August 1999 Izmit earthquake, to quantify the interseismic strain accumulation pattern in the Marmara Sea region.
Abstract: The Marmara Sea region is deforming along the branches of the North Anatolian Fault (NAF), which is the boundary between the Anatolian and the Eurasian plates. We evaluate Global Positioning System (GPS) measurements performed from 1992 to 1999, up to the 17 August 1999 Izmit earthquake, to quantify the interseismic strain accumulation pattern in the Marmara Sea region. We compute interseismic velocities in a frame fixed to the Eurasian plate at 136 GPS points. To compute the frame-independent strain rates, we first smooth the north-south and the east-west velocity components separately to obtain the values at grid nodes, and then we compute directional derivatives and strain rates. Shear-strain rates reveal that the Marmara Sea region is within the plate boundary deformation zone having a width of about 110 km. The largest shear-strain rate accumulation is along the northern branch of the NAF, with maximum shear-strain rate reaching 220 nstrain/yr in the Marmara Sea. We calculate clockwise rigid body rotation rates with a maximum of 10 deg/m.y. along the northern branch while the Anatolian plate rotates anticlockwise. Dilatation rates display adjacent local tensional and compressional areas in the east-west direction within the Marmara Sea. Assuming the uniform simple shear, we compute the NAF slip rates vary between 11 and 26 mm/yr, with a minimum around Izmit, and increase east and west of Izmit. Manuscript received 30 August 2000.

55 citations


Cited by
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TL;DR: In this paper, a global set of present plate boundaries on the Earth is presented in digital form, taking into account relative plate velocities from magnetic anomalies, moment tensor solutions, and geodesy.
Abstract: [1] A global set of present plate boundaries on the Earth is presented in digital form. Most come from sources in the literature. A few boundaries are newly interpreted from topography, volcanism, and/or seismicity, taking into account relative plate velocities from magnetic anomalies, moment tensor solutions, and/or geodesy. In addition to the 14 large plates whose motion was described by the NUVEL-1A poles (Africa, Antarctica, Arabia, Australia, Caribbean, Cocos, Eurasia, India, Juan de Fuca, Nazca, North America, Pacific, Philippine Sea, South America), model PB2002 includes 38 small plates (Okhotsk, Amur, Yangtze, Okinawa, Sunda, Burma, Molucca Sea, Banda Sea, Timor, Birds Head, Maoke, Caroline, Mariana, North Bismarck, Manus, South Bismarck, Solomon Sea, Woodlark, New Hebrides, Conway Reef, Balmoral Reef, Futuna, Niuafo'ou, Tonga, Kermadec, Rivera, Galapagos, Easter, Juan Fernandez, Panama, North Andes, Altiplano, Shetland, Scotia, Sandwich, Aegean Sea, Anatolia, Somalia), for a total of 52 plates. No attempt is made to divide the Alps-Persia-Tibet mountain belt, the Philippine Islands, the Peruvian Andes, the Sierras Pampeanas, or the California-Nevada zone of dextral transtension into plates; instead, they are designated as “orogens” in which this plate model is not expected to be accurate. The cumulative-number/area distribution for this model follows a power law for plates with areas between 0.002 and 1 steradian. Departure from this scaling at the small-plate end suggests that future work is very likely to define more very small plates within the orogens. The model is presented in four digital files: a set of plate boundary segments; a set of plate outlines; a set of outlines of the orogens; and a table of characteristics of each digitization step along plate boundaries, including estimated relative velocity vector and classification into one of 7 types (continental convergence zone, continental transform fault, continental rift, oceanic spreading ridge, oceanic transform fault, oceanic convergent boundary, subduction zone). Total length, mean velocity, and total rate of area production/destruction are computed for each class; the global rate of area production and destruction is 0.108 m2/s, which is higher than in previous models because of the incorporation of back-arc spreading.

1,853 citations

Journal ArticleDOI
TL;DR: In this article, an elastic block model was developed to constrain present-day plate motions (relative Euler vectors), regional deformation within the interplate zone, and slip rates for major faults.
Abstract: [1] The GPS-derived velocity field (1988–2005) for the zone of interaction of the Arabian, African (Nubian, Somalian), and Eurasian plates indicates counterclockwise rotation of a broad area of the Earth's surface including the Arabian plate, adjacent parts of the Zagros and central Iran, Turkey, and the Aegean/Peloponnesus relative to Eurasia at rates in the range of 20–30 mm/yr. This relatively rapid motion occurs within the framework of the slow-moving (∼5 mm/yr relative motions) Eurasian, Nubian, and Somalian plates. The circulatory pattern of motion increases in rate toward the Hellenic trench system. We develop an elastic block model to constrain present-day plate motions (relative Euler vectors), regional deformation within the interplate zone, and slip rates for major faults. Substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below ∼1–2 mm/yr, including central and eastern Anatolia (Turkey), the southwestern Aegean/Peloponnesus, the Lesser Caucasus, and Central Iran. Geodetic slip rates for major block-bounding structures are mostly comparable to geologic rates estimated for the most recent geological period (∼3–5 Myr). We find that the convergence of Arabia with Eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the Caucasus and Zagros mountain belts around the periphery of the collision zone. In addition, we find that the principal boundary between the westerly moving Anatolian plate and Arabia (East Anatolian fault) is presently characterized by pure left-lateral strike slip with no fault-normal convergence. This implies that “extrusion” is not presently inducing westward motion of Anatolia. On the basis of the observed kinematics, we hypothesize that deformation in the Africa-Arabia-Eurasia collision zone is driven in large part by rollback of the subducting African lithosphere beneath the Hellenic and Cyprus trenches aided by slab pull on the southeastern side of the subducting Arabian plate along the Makran subduction zone. We further suggest that the separation of Arabia from Africa is a response to plate motions induced by active subduction.

1,609 citations

Journal ArticleDOI
08 Dec 2000-Science
TL;DR: Seismic tomography models of the three-dimensional upper mantle velocity structure of the Mediterranean-Carpathian region provide a better understanding of the lithospheric processes governing its geodynamical evolution.
Abstract: Seismic tomography models of the three-dimensional upper mantle velocity structure of the Mediterranean-Carpathian region provide a better understanding of the lithospheric processes governing its geodynamical evolution. Slab detachment, in particular lateral migration of this process along the plate boundary, is a key element in the lithospheric dynamics of the region during the last 20 to 30 million years. It strongly affects arc and trench migration, and causes along-strike variations in vertical motions, stress fields, and magmatism. In a terminal-stage subduction zone, involving collision and suturing, slab detachment is the natural last stage in the gravitational settling of subducted lithosphere.

1,492 citations

Journal ArticleDOI
TL;DR: GMT 6 defaults to classic mode and thus is a recommended upgrade for all GMT 5 users, and new users should take advantage of modern mode to make shorter scripts, quickly access commonly used global data sets, and take full advantage of the new tools to draw subplots, place insets, and create animations.

1,098 citations

Journal ArticleDOI
TL;DR: A network of 27 GPS sites was implemented in Iran and northern Oman to measure displacements in this part of the Alpine-Himalayan mountain belt as mentioned in this paper, and the results of two surveys performed in 1999 September and 2001 October.
Abstract: SUMMARY A network of 27 GPS sites was implemented in Iran and northern Oman to measure displacements in this part of the Alpine‐Himalayan mountain belt. We present and interpret the results of two surveys performed in 1999 September and 2001 October. GPS sites in Oman show northward motion of the Arabian Plate relative to Eurasia slower than the NUVEL-1A estimates (e.g. 22 ± 2m m yr −1 at N8 ◦ ± 5 ◦ E instead of 30.5 mm yr −1 at N6 ◦ E at Bahrain longitude). We define a GPS Arabia‐Eurasia Euler vector of 27.9 ◦ ± 0.5 ◦ N, 19.5 ◦ ± 1.4 ◦ E, 0.41 ◦ ± 0.1 ◦ Myr −1 . The Arabia‐Eurasia convergence is accommodated differently in eastern and western Iran. East of 58 ◦ E, most of the shortening is accommodated by the Makran subduction zone (19.5 ± 2m m yr −1 ) and less by the Kopet-Dag (6.5 ± 2m m yr −1 ). West of 58 ◦ E, the deformation is distributed in separate fold and thrust belts. At the longitude of Tehran, the Zagros and the Alborz mountain ranges accommodate 6.5 ± 2m m yr −1 and 8 ± 2m m yr −1 respectively. The right-lateral displacement along the Main Recent Fault in the northern Zagros is about 3 ± 2m m yr −1 , smaller than what was generally expected. By contrast, large rightlateral displacement takes place in northwestern Iran (up to 8 ± mm yr −1 ). The Central Iranian Block is characterized by coherent plate motion (internal deformation < 2m m yr −1 ). Sites east of 61 ◦ E show very low displacements relative to Eurasia. The kinematic contrast between eastern and western Iran is accommodated by strike-slip motions along the Lut Block. To the south, the transition zone between Zagros and Makran is under transpression with right-lateral displacements of 11 ± 2m m yr −1 .

1,013 citations