مجله زمین ساخت
پیاپی 23 (پاییز 1401)

The NNW-SSE trending Âj fault parallel to the Naein-Baft fault zone in the west of micro-continent of Central Iran, starts from the south of Mehriz and passes through the Urumieh-Dokhtar magmatic arc, to the southern margin of the Sanandaj- Sirjan metamorphic zone in south of Iran with N350 trend. The structural analysis of this fault in Urumieh- Dokhtar magmatic arc (Dehaj-Sarduiyeh magmatic belt) indicates a dextral oblique-slip mechanism. The paleo-stress analysis based on the data taken from the fault surfaces indicates the direction of the maximum stress in N040 parallel with the contractional movements of the Arabian plate towards the Central Iran. The Âj fault has caused many changes in the morphology of this area, one of the most important of which is the penetration of sub-volcanic dacite-rhyodacite plugs along its length. In the south of the studied area, this fault has caused the cut and dextral displacement of the ophiolites and Shahr-e-Babak fault zone. The Âj fault zone is active, because some rivers in its length are dextral displacement.

Garagheh closed basin is located in the west and northwest of Zahedan city and in the middle of Sistan Suture Zone. The presence of this basin with a large area that located in a shear-compressional Sistan Suture Zone that surrounded by numerous faults can be a subject for study of active tectonics in this area. Based on field study and the relationship between tectonic structures, the development of this basin has been investigated. We applied the geomorphic indices such as mountain-front sinuosity (SMF), asymmetry factor of drainage basin (AF), hypsometric integral (HI), basin shape (BS), mean axial slope of channel (MASC), valley floor width –valley height ratio (VF), relative assessment of tectonic activity (Iat) to evaluate tectonic activity of 378 sub-basins. The results suggest that the main basin is active and asymmetric but the activity of sub-basins are different throughout the study area. High active sub-basins are mainly located around the main basin and associated with active faults but less active basins are mainly located in the center. The relationship between shape of main basin and active faults shows, depending on the shape of the basin, the faults are close to each other in the north and northwest and far apart in the south and southeast. These results suggest a counter clockwise rotation of faults caused a tectonic rotation that creates a transtensional deformation that form a closed Garagheh Basin.

The active fault of North Sarbisheh from the main branches of the Nehbandan fault zone, in the middle part of the Sistan suture zone has two trends, northwest-southeast and east-west .Due to the fact that the North Sarbisheh fault consists of different segmentation, the fractal dimensions of the streams were calculated in four parts of Bijaem, Baghestan, Rumashk and Dastghich. The average fractal dimensions of the streams in order to compare the tectonic dynamics in this fault zone, in the Baghestan segment, is 1.98 compared to the parts of the Dastghich, Rumashk and Bijaem at 1.96 due to the linearity of the waterways and the density of the lower surface congestion in these three parts, indicating Most of these tectonic activities are related to Baghestan fault zone. Comparing the fractal dimensions of the waterways and, accordingly, the direction of the fault in different parts and the evidence obtained, shows that the deformation progress of the present era is towards the eastern part of the fault.

Since in extensional environments less differential stress is needed for rock fracture, earthquakes are usually triggered with less energy. In the present study, by determining the amount of energy along the normal fault during the collapse of the hanging wall block, which is dependent on the calculation of the volume of the hanging wall block, while achieving the main goal of the study, geometrical data including the volume of the hanging wall block can be obtained. The main foundation of the current seismic model is based on the theory of elastic rebound, in which the release of accumulated elastic energy occurs during the interseismic period. Finite elements, including triangular linear Lagrange elements and conditions of lateral tension changes at the base of the lithosphere affected by viscous-plastic stretching in the upper mantle, have been used for numerical analysis. The results showed that the increase in the magnitude of the earthquake is affected by the increase in the length of the rupture, and the amount of finite deformation caused by seismic sequences is related to the length of the rupture and is about three times the depth of the hypocenter. Assuming a dip of about 45 degrees for the conjugate wedge with the fault activated during the nucleation of an earthquake, the three volumes of the falling wedge during the earthquake stage well indicate the direct correlation of the fault length with the displacement of the fault and the volume of the hanging wall block.

The Zagros fold-thrust belt's Fars region is crucial for the placement of enormous gas reserves in Permo-Triassic carbonate sediments. Therefore, it's important to investigate the potential impact of the Hendurabi fault on the expansion of hydrocarbon traps in the inner Fars region. This will help advance the exploration goals of hydrocarbon materials. The study area is located in the inner Fars region of the Zagros thrust belt. In this research, maps of equal thickness have been prepared, analyzed, and evaluated based on drilling well data in the region, using ArcGIS software. Given the importance of changes and evolutions of the hydrocarbon system in the exploration of hydrocarbon resources, the function of the main basement faults with the role of controlling the bottom of the sedimentary basins, along with the changes that have occurred, can change the nature of a hydrocarbon system and the created hydrocarbon traps. Overall, the activity of the Hendurabi fault has caused thickness changes on the sides of the fault, confirmed by the uplifts and subsidence’s created on the sides of the Hendurabi fault at the same time as the deposition of some formations such as Dashtak. The activity of this fault as a controlling fault of the sedimentary basin floor during the sedimentation of formations like Dashtak is confirmed. Based on the obtained results, the southeastern area of the studied area, containing hydrocarbon traps, is suitable for exploration due to the adequate and appropriate thickness and suitable depth of the Kangan reservoir horizon and Dashtak caprock.

The study area is located in the Tarom Sofla region, which is located in the central Alborz tectonic zone. Morphotectonic indices of the region provide useful and valuable variations, especially in determining tectonic activity. The tectonics of the region, which caused the bending of the Alborz belt in the study area, is one of the main factors controlling the morphotectonic indicators in the region. Alborz orogenic belt has important active faults around the Takestan bend which may affect the activity potential of the area. In this research, the tectonic activity of the region has been investigated by calculation of morphotectonic indices including stream length-gradient index (Sl), ratio of valley-floor width to valley height index (Vf), hypsometric integral index (Hi), drainage basin shape (Bs), stream sinuosity index (S), drainage basin asymmetry index (Af), transverse topographic symmetry index (T), and the planar surface density index (P). This study has been carried out using geological and topographical maps together with remote sensing of Landsat images, by using Arc GIS and Global mapper softwares. Finally, the results have been estimated using the evaluation of relative tectonic activity (Iat). The indicative values of Iat indicate high tectonic activity in the middle part, and moderate and low tectonic activity in the northwest and southeast part of the area, respectively.