| 1. |
- Vernant, P, et al.
(författare)
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Deciphering oblique shortening of central Alborz in Iran using geodetic data
- 2004
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Ingår i: Earth and Planetary Science Letters. - : Elsevier. - 0012-821X. ; 223:1-2, s. 177-185
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Tidskriftsartikel (refereegranskat)abstract
- The Alborz is a narrow (100 km) and elevated (3000 m) mountain belt which accommodates the differential motion between the Sanandaj–Sirjan zone in central Iran and the South Caspian basin. GPS measurements of 12 geodetic sites in Central Alborz between 2000 and 2002 allow to constrain the motion of the belt with respect to western Eurasia. One site velocity on the Caspian shoreline suggests that the South Caspian basin moves northwest at a rate of 6±2 mm/year with respect to western Eurasia. North–South shortening across the Alborz occurs at 5±2 mm/year. To the South, deformation seems to extend beyond the piedmont area, probably due to active thrusting on the Pishva fault. We also observe a left-lateral shear of the overall belt at a rate of 4±2 mm/year, consistent with the geological motion observed along E–W active strike-slip faults inside the belt (e.g., the Mosha fault).
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| 2. |
- Vernant, P, et al.
(författare)
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Present-day crustal deformation and plate kinematics in the Middle East constrained by GPS measurements in Iran and northern Oman
- 2004
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 157:1, s. 381-398
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Tidskriftsartikel (refereegranskat)abstract
- 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 ± 2 mm 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 ± 2 mm yr−1) and less by the Kopet-Dag (6.5 ± 2 mm 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 ± 2 mm yr−1 and 8 ± 2 mm yr−1 respectively. The right-lateral displacement along the Main Recent Fault in the northern Zagros is about 3 ± 2 mm yr−1, smaller than what was generally expected. By contrast, large right-lateral displacement takes place in northwestern Iran (up to 8 ± mm yr−1). The Central Iranian Block is characterized by coherent plate motion (internal deformation <2 mm 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 ± 2 mm yr−1.
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| 3. |
- Bayer, R, et al.
(författare)
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Active deformation in Zagros-Makran transition zone inferred from GPS measurements
- 2006
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Ingår i: Geophysical Journal International. ; 165:1, s. 373-381
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Tidskriftsartikel (refereegranskat)abstract
- The Bandar Abbas-Strait of Hormuz zone is considered as a transition between the Zagros collision and the Makran oceanic subduction. We used GPS network measurements collected in 2000 and 2002 to better understand the distribution of the deformation between the collision zone and the Makran subduction. Analysing the GPS velocities, we show that transfer of the deformation is mainly accommodated along the NNW–SSE-trending reverse right-lateral Zendan–Minab–Palami (ZMP) fault system. The rate is estimated to 10 ± 3 mm yr−1 near the faults. Assuming that the ZMP fault system transfers the motion between the Makran–Lut Block and the Arabian plate, we estimate to 15 mm yr−1 and 6 mm yr−1, respectively, the dextral strike-slip and shortening components of the long-term transpressive displacement. Our geodetic measurements suggest also a 10–15 km locking depth for the ZMP fault system. The radial velocity pattern and the orientation of compressive strain axes around the straight of Hormuz is probably the consequence of the subducting Musandam promontory. The N–S Jiroft–Sabzevaran (JS) fault system prolongates southwards the dextral shear motion of the Nayband–Gowk (NG) fault system at an apparent rate of 3.1 ± 2.5 mm yr−1. The change from strong to weak coupling for underthrusting the Arabian plate beneath the Zagros (strong) and the Makran (weak) may explain the dextral motion along the ZMP, JS/NG and Neh–Zahedan fault systems which transfer the convergence from a broad zone in the western Iran (Zagros, Tabriz fault system, Alborz, Caucasus and Caspian sea surroundings) to Makran subduction.
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| 4. |
- Nilforoushan, Faramarz, et al.
(författare)
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GPS network monitors the Arabia-Eurasia collision deformation in Iran
- 2003
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 77, s. 411-422
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Tidskriftsartikel (refereegranskat)abstract
- The rate of crustal deformation in Iran due to the Arabia–Eurasia collision is estimated. The results are based on new global positioning system (GPS) data. In order to address the problem of the distribution of the deformation in Iran, Iranian and French research organizations have carried out the first large-scale GPS survey of Iran. A GPS network of 28 sites (25 in Iran, two in Oman and one in Uzbekistan) has been installed and surveyed twice, in September 1999 and October 2001. Each site has been surveyed for a minimum observation of 4 days. GPS data processing has been done using the GAMIT-GLOBK software package. The solution displays horizontal repeatabilities of about 1.2 mm in 1999 and 2001. The resulting velocities allow us to constrain the kinematics of the Iranian tectonic blocks. These velocities are given in ITRF2000 and also relative to Eurasia. This last kinematic model demonstrates that (1) the north–south shortening from Arabia to Eurasia is 2–2.5 cm/year, less than previously estimated, and (2) the transition from subduction (Makran) to collision (Zagros) is very sharp and governs the different styles of deformation observed in Iran. In the eastern part of Iran, most of the shortening is accommodated in the Gulf of Oman, while in the western part the shortening is more distributed from south to north. The large faults surrounding the Lut block accommodate most of the subduction–collision transition.
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| 5. |
- Walpersdorf, A, et al.
(författare)
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Difference in the GPS deformation pattern of North and Central Zagros (Iran)
- 2006
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 167:3, s. 1077-1088
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Tidskriftsartikel (refereegranskat)abstract
- Measurements on either side of the Kazerun fault system in the Zagros Mountain Belt, Iran, show that the accommodation of the convergence of the Arabian and Eurasian Plates differs across the region. In northwest Zagros, the deformation is partitioned as 3–6 mm yr−1 of shortening perpendicular to the axis of the mountain belt, and 4–6 mm yr−1 of dextral strike-slip motion on northwest–southeast trending faults. No individual strike-slip fault seems to slip at a rate higher than ∼2 mm yr−1. In southeast Zagros, the deformation is pure shortening of 8 ± 2 mm yr−1 occurring perpendicular to the simple folded belt and restricted to the Persian Gulf shore. The fact that most of the deformation is located in front of the simple folded belt, close to the Persian Gulf, while seismicity is more widely spread across the mountain belt, confirms the decoupling of the surface sedimentary layers from the seismogenic basement. A comparison with the folding and topography corroborates a southwestward propagation of the surface deformation. The difference in deformation between the two regions suggests that right-lateral shear cumulates on the north–south trending Kazerun strike-slip fault system to 6 ± 2 mm yr−1.
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| 6. |
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| 7. |
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| 8. |
- Schreurs, G., et al.
(författare)
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Analogue benchmarks of shortening and extension experiments
- 2006. - 253
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Ingår i: <em> </em>Analogue and Numerical Modeling of Crustal-Scale Processes. - : Geological Society of London. - 1862391912 ; , s. 1-27
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Bokkapitel (refereegranskat)abstract
- We report a direct comparison of scaled analogue experiments to test thereproducibility of model results among ten different experimental modelling laboratories.We present results for two experiments: a brittle thrust wedge experiment and a brittleviscousextension experiment. The experimental set-up, the model construction technique,the viscous material and the base and wall properties were prescribed. However, each laboratoryused its own frictional analogue material and experimental apparatus. Comparisonof results for the shortening experiment highlights large differences in model evolutionthat may have resulted from (1) differences in boundary conditions (indenter or basal-pullmodels), (2) differences in model widths, (3) location of observation (for example, sidewallversus centre of model), (4) material properties, (5) base and sidewall frictional properties,and (6) differences in set-up technique of individual experimenters. Six laboratories carriedout the shortening experiment with a mobile wall. The overall evolution of their models isbroadly similar, with the development of a thrust wedge characterized by forward thrustpropagation and by back thrusting. However, significant variations are observed inspacing between thrusts, their dip angles, number of forward thrusts and back thrusts, andsurface slopes. The structural evolution of the brittle-viscous extension experiments issimilar to a high degree. Faulting initiates in the brittle layers above the viscous layer in close vicinity to the basal velocity discontinuity. Measurements of fault dip angles and faultspacing vary among laboratories. Comparison of experimental results indicates an encouragingoverall agreement in model evolution, but also highlights important variations in thegeometry and evolution of the resulting structures that may be induced by differences inmodelling materials, model dimensions, experimental set-ups and observation location
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