Active Tectonics and Its Impact on the Evolution of the Quaternary Landforms in Tabass Region, Iran

  The active deformation in Iran is caused by Arabia- Eurasia convergence. This agent creates morphotectonic landforms in each part of Iran. The importance of understanding the tectonic regime in the direction of morphotectonic studies of each district, and the potential hazards of land area and thus make their management and preventive measures necessary to reduce their effects on the role of human structures. In the in most studies related to the recognition of the status of the first step in the morphotectonic region, paying special attention to the superficial geomorphic evidence and linear, then the data of Geophysics supplement and seismicity region. The evidence of active tectonic regime in the dominant understanding of the tectonic and mechanism of folds – fault is extremely helpful to identification of it. Study the evolution of the Quaternary, including geometric geomorphologically drainage action; and alluvial fans are factors that can help them to the position of the land area of each area. In this study, try to study active tectonic marker and landforms with evidence reviews and located in median of Shotori Mountains and Tabas Playa, landforms and evolutions of them by recognizing of deformation and stream patterns. In this study Folds, alluvial fans, earthquakes, faults, streams and cliffs has been studied.
Method and materials
In order to study area, we use remote sensing capabilities such as; sentinel, landsat 8, Quickbirds and DEM30m to recognize the structural of surface landforms (alluvial fans, folds) and lines (drainage networks, rivers, faults, cliffs). Following, we used ENVI and ArcGIS softwares to detection and drawing of maps. We used seismic data of Institute of Geophysics (2006-2016) and USGS (1900-2016). Finally, the geometric display of their displacement was done in Focal Mechanisms.
Discussion and results (Evidence of active tectonics)
Alluvial fans;
The study of satellite imagery and geological maps of the area, especially in the west of the Shotori Mountains, reveals large and numerous alluvial fans, sometimes created to the desert along the lower sections and developed and expanded by the sedimentation of seasonal and permanent rivers. These alluvial fans are joined in most parts of southern Tabas. According to the criteria for the differentiation of alluvial fans from each other, three types of old, active and midway are identified at the confluence of the Tabas playa and Shotori Mountains as continuous.
Folds and antecedences;
There are several new folds in quaternary sediments in median of Shotori Mountains and Tabas Playa. One of them cases is Tabas (or Sardar) fold in north of Tabs city. This fold appearance among the old alluvial fan Tabas and Sardar River excavated hardly it. As Sardar River make a deep gorgeous (canyon) through this fold. Another folds like Tabas fold are; Fahlanj fold, north Fahlanj fold, Fosha fold.
Cliffs;
The origin of the cliffs or tectonic cliffs of the study area are the strike slip and reverse faults. As Tabas fault cause sever cliff more than 100 meter by North-South direction.
Faults;
Faults are important tectonic elements in the creation of various early landforms such as Horst, Graben, Thrust, etc. more of faults in the study area to follow Nayband fault system N-S direction. In the center of the fold east of the village of Estahpak, there is an active strike-slip fault series that displaces sandstone and conglomerate sediments of Miocene up to 130 meters. Estahpak fault and its lateral branches in some cases displaced the Quaternary sedimentary layers up to 330 meters. In Fosha fold, strike slip displacement Quaternary up 350 meters.
Stream and rivers (Drainages networks);
Stream and rivers are so sensitive to tectonic and response to it quickly. Straight Right Stroke Fault Estahpak causes displacement of streams up to 390 meters.
Geophysics;
According to seismic data from the US Geological Survey, from 1973 to 2016, about 60 earthquakes ranged from 4.5 to 7.4 magnitudes has been occurred. Meanwhile, the average depth of earthquakes is at an approximate depth of 31 km, which is the earthquake centers between depths of 58 - 2 km. The focus of earthquake centers at the beginning of the mountain front and immediately after the occurrence of roughness. In 1979, after the Tabas earthquake, a fracture with a length of 80 kilometers along the Tabas fault was created and killed more than 25000 people by 7.6 magnitude. Indications of active, fault-driven folding and drainage incision, fans and cliffs are present in the landscape in Tabas. The morphotectonic and geomorphologic evidence of the Tabas area indicates the strong impact of ground forces building on surface landforms such as; alluvial fans, folds, stream and rivers, cliffs, faults. The effect of the new tectonic forces on the alluvial fans is the formation of a multi-stage convex alluvial fans or, in other words, three layers in the southern slopes of Tabas, and the growth of the folds. The anticlines are also other morphotectonic evidence in the Tabas area. The superficial and linear morphotectonic evidence in Tabas indicates the high tension and the strong dynamics of ground forces, as well as the existence of faults with thrust, strike slip, and hybrid mechanisms. Overall, the aggregate evidence also suggests that the tectonic forces of the eastern Playa Tabas are more active than the western highlands section. The presence of fans, faults and anticlines in the eastern part of the Tabas playa is due to this.
Key words; Tabass, Active Tectonics, Morphotectonic, Quaternary landforms