modern research physics

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Torud fault is located in 110 Km away from the south of Damghan and trends ENE-WSW that is approximately E-W at its west end. In this termination region, observed structures indicate a special aspect of strike-slip fault terminations. These structures are of two sets: the first set are structures trending approximately N-S and are mainly compressional ones such as thrust faults and folds both verging to the east. These structures are in Paleozoic and Mesozoic rocks. Right lateral and normal shear structures, microfolds, foliations, and lineations are also associated with them. The second set are structures having NE-SW direction and include open gentle folds and younger thrusts which both verge to the south. They are mainly in Cenozoic and younger rocks but have made notable changes in older rocks too. Direction of Torud Mountain and its surrounding faults to direction of Arabia –Eurasia convergence, and effects of rotation and compression of Lut block and movements of its surrounding faults, led to transpressional deformation in the area under studyThe direction of slip in this system was related to tactors that were mentioned above and has been changed in response to the local changes of stress field.Strain in some locations has been partitioned into two components: shearing and compression. They operated contempo-rarily or in two separate times. Other minor structures such as Reidel and P shears and folds of wrench tectonic also exist as they are predictable in shear zones.

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Southern flank of the East– Central Alborz Mountain is consisting of several tectonic elements, which were introduced and analyzed, in this paper. This region is including a complex thrust system at north and a widespread foreland basin at south of Alborz– Central Iran border zone. Two significance curvatures at Alborz Mountain belt that have introduced here such as Neyshabur– Esfarayen– Shahrud Syntaxis and Damghan– Semnan– Qazvin Salient, had been created by change in trend of Alborz from NW– SE to NE–SW. According to this research, creative and activities of the fault systems in a sinistral displacement shear zone that had been elongated from south Semnan to north Gonbad–e Kavus was suggested as a cause to forming of above curvatures and thinning of Alborz width at north Bastam. Therefore, deformation in this region is a combination of compressional and left–lateral strike slip components that (Transpression) demonstrated by field evidences and focal mechanism solutions.