No abstract

No abstract

Lateral ofsets in the pattern of seismicity along the Zagros fold and thrust belt indicate that transverse faults segmenting the Arabian basement are active deep-seated strike-slip faults. The dominant NW-SE trending features ofthe belt have undergone repeated horizontal displacements along these transverse faults. These reactivated basement faults, which are inherited from the Pan-African construction phase, controlled both deposition of the Phanerozoic cover before Tertiary-Recent deformation of the Zagros and probably the entrapment of hydrocarbons on the NE margin of Arabia and in the Zagros area. We have used observations of faulting recognized on Landsat satellite images, in conjunction with the spatial distribution of earthquakes and their focal mechanism solutions, to infer a tectonic model for the Zagros basement.Deformation in the NW Zagros appears to be concentrated on basement thrusts and a few widely-spaced north-south trending strike-slip faults which separate major structural segments. In the SE Zagros, two main structural domains can be distinguished. A domain of NNWtrending right-lateral faults in the northern part of the SE Zagros implies that fault-bounded blocks are likely to have rotated anticlockwise about vertical axes relative to both Arabia and Central Iran. In contrast, the predominance of NNE-trending left-lateral faults in the southern part of the SE Zagros implies that fault-bounded blocks may have rotated clockwise about vertical axes. We propose a tectonic model in which crustal blocks bounded by strike-slip faults in a zone of simple shear rotate about vertical axes relative to both Arabia and Central Iran. The presence of domains of strike-slip and thrust faulting in the Zagros basement suggest that some of the convergence between Arabia and Central Iran is accommodated by rotation andpossible lateral movement of crust along the belt by strike-slip faults, as well as by obvious crustal shortening and thickening along thrust faults.

: We report a direct comparison of scaled analogue experiments to test the reproducibility of model results among ten different experimental modelling laboratories. We present results for two experiments: a brittle thrust wedge experiment and a brittleviscous extension experiment. The experimental set-up, the model construction technique, the viscous material and the base and wall properties were prescribed. However, each laboratory used its own frictional analogue material and experimental apparatus. Comparison of results for the shortening experiment highlights large differences in model evolution that may have resulted from (1) differences in boundary conditions (indenter or basal-pull models), (2) differences in model widths, (3) location of observation (for example, sidewall versus centre of model), (4) material properties, (5) base and sidewall frictional properties, and (6) differences in set-up technique of individual experimenters. Six laboratories carried out the shortening experiment with a mobile wall. The overall evolution of their models is broadly similar, with the development of a thrust wedge characterized by forward thrust propagation and by back thrusting. However, significant variations are observed in spacing between thrusts, their dip angles, number of forward thrusts and back thrusts, and surface slopes. The structural evolution of the brittle-viscous extension experiments is similar to a high degree. Faulting initiates in the brittle layers above the viscous layer in

No abstract

SUMMARY The continental collision between the African and Eurasian plates resulted in a tectonically young and complex deformation in the Iranian plateau. The present‐day Iranian plateau is characterized by diverse tectonic domains including the continental collisions (e.g. Zagros and Alborz) and the oceanic plate subduction (e.g. Makran). Partitioned waveform inversion method is used here to image the S‐velocity structure of the upper‐mantle and Moho‐depth variations in the Iranian plateau. Of nearly 3000 waveforms originally selected for the analysis, we have fitted 974 waveforms from 101 events and 39 stations which result in 11 688 linear constraints on the upper‐mantle S‐velocity structure and Moho depth for the region. Our new seismic images show seismically faster upper mantle beneath the Zagros and the Arabian Plate compared to the Central Iran and Alborz. This high‐velocity anomaly has descended beneath the Central Iran along the Main Zagros Thrust. Across the Zagros collision zone, the tomographic images show a slab stagnation in the transition zone (at about 410 km depth) in the form of a horizontal high‐velocity zone which does not penetrate the deeper parts of the mantle. The lowest S‐velocities are concentrated beneath the Central Iran and Alborz. According to our velocity models, a strong high‐velocity anomaly is resolved beneath the trapped South Caspian Basin with clear indication of westward underthrusting beneath the Talesh and western Alborz. In Makran, southeast Iran, there is a clear evidence of subduction of oceanic crust of the Arabian plate beneath the Makran belt which is correlated with seismicity pattern across the Makran zone. Also, the inverted Moho map using a priori information of crustal thickness constraints shows the large crustal thickness beneath the Zagros suture zone (in some places to a maximum depth of 65 km) which indicates the influence of crustal thickening and shortening beneath Arabian–Eurasian Plate boundary. A significantly crustal thinning is observable across the South Caspian Basin compared to its margins.

No abstract

Please note that this is an author-produced PDF of an article accepted for publication following peer review. The definitive publisher-authenticated version is available on the publisher Web site.