Tectonic mechanical properties of the Alborz region, Iran
In this study for better analysis of geo-hazard on two parameters were focused: geodynamics and mechanical property of the orogen. The Alborz region in the northern Iran was selected as the study area. The Alborz mountain range in Iran is an ideal object to investigate the potential influence of past tectonic regimes on the future evolution of this long-lived convergence. For this purpose, previous geodynamic results were reviewed and compiled with data on present day tectonic activity at crustal and upper mantle scale. Previously published models indicate that the Iran Plate was subjected to a series of extensional and compressional tectonic regimes, ultimately linked with the opening and closure of the Tethys Ocean and related basins. Two subduction-collision cycles are recognized: one cycle occurred as a result of the subduction of the Iran Plate beneath the Turan Plate and in this cycle the subduction phase ceased in the Cenozoic and since the Cenozoic it is in a collision phase. The other cycle took place as a result of the subduction of the Arabian Plate beneath the Iran Plate, and in this cycle the subduction phase began in the Mesozoic and is ending now. Thus, the current tectonic situation in the Alborz is a direct consequence from the ongoing Cenozoic subduction-collision cycle. GPS and earthquake data indicate that the Alborz region, resulting from the collision of the Iran Plate with the Turan Plate, is still an area of recently active compression. Moho and tomographic data show that there is no connection between slab remnants of the oceanic crust and the Iran Plate. Furthermore, the Moho beneath the central Alborz is about 20 km deeper than in surrounding areas, indicating further advancement of collision there. However, the collision is continuing and the shorted area between the Iran Plate and the Turan Plate may increase. During the crustal thickening, a deep Moho area can also develop. This evolution can be expected in the tectonic cycle between the Arabian Plate and the Iran Plate, and also other places of the Alpine-Himalayan Belt (AHB), such as the Caucasus region.
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