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The character of convergence along the Arabian-Iranian plate boundary changes radically eastward from the Zagros ranges to the Makran region. This appears to be due to collision of continental crust in the west, in contrast to subduction of oceanic crust in the east. The Makran subduction zone with a length of about 900 km display progressively older and highly deformed sedimentary units northward from the coast, together with an increase in elevation of the ranges. North of the Makran ranges are large subsiding basins, flanked to the north by active volcanoes. Based on 2D seismic reflection data obtained in this study, the main structural provinces and elements in the Gulf of Oman include: (i) the structural elements on the northeastern part of the Arabian Plate and, (ii) the Offshore Makran Accretionary Complex. Based on detailed analysis of these data on the northeastern part of the Arabian Plate five structural provinces and elements-the Musendam High, the Musendam Peneplain, the Musendam Slope, the Dibba Zone, and the Abyssal Plain have been identified. Further, the Offshore Makran Accretionary Complex shown is to consist Accretionary Prism and the For-Arc Basin, while the Accretionary Prism has been subdivided into the Accretionary Wedge and the Accreted/Colored Mélange. Lastly, it is important to note that the Makran subduction zone lacks the trench. The identification of these structural elements should help in better understanding the seismicity of the Makran region in general and the subduction zone in particular. The 1945 magnitude 8.1 tsunamigenic earthquake of the Makran and some other historical events are illustrative of the coastal region's vulnerability to future tsunami in the area, and such data should be of value to the developing Indian Ocean Tsunami Warning System.

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We present and use seismic images to constrain possible scenarios for the evolution of the Middle Miocene Gachsaran Formation in the Central Iranian Zagros during the Neogene folding. This evaporitic sequence plays an important role in sealing the Oligocene–Miocene Asmari reservoirs in the Dezful Embayment and offshore regions. It was deposited in the flexural basin south of the Mountain Front Fault, during the progressive southwestward propagation of the Zagros folding. Its thickness changes very rapidly from several hundred to more than 4000 m. This thickness variation is related to faulting, folding and flow. Seismic and subsurface data show that the Gachsaran evaporite sequence is a major disharmonic level in the Dezful Embayment and shallow, molassic synclines often overlie anticlinal axes at depth. The lithological composition of the Gachsaran Formation is mainly a combination of salt, shale and anhydrite, which have a high interval velocity contrast. Anomalous velocity behaviours of these sedimentary units after deformation affect the seismic quality of the surrounding area, especially the southern flank of the main anticline structures.

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