Evaluating the effects of fault tectonics on the geomorphology of Zanjanrud basin using remote-sensing and geomorphometry techniques

ABSTRACT
The geomorphology of the Zanjanroud basin is affected by the active tectonic zones resulting from the interaction of the Soltanieh, Zanjan, Tarem, and Manjil faults and the faults that have been investigated more closely in this research. The interaction of these faults has made this basin in the form of a small high plateau, heterogeneous compared to the surrounding areas and a suitable place for the establishment of human settlements. In this research, remote sensing and geomorphometric techniques have been used to identify the lineaments and tectonic evidence in order to discover the tectonic effect on the geomorphology of the basin. The contour lines have been converted into a map after checking with the help of telemetry, geomorphometry and field techniques. Then, by analyzing and interpreting the evidence, the relationship between the dynamic pattern of the faults and its effects on the morphology of different landforms is presented with an emphasis on the interactive reconstruction of drainage networks and faults. The results show that the active tectonics of the faults are concentrated towards the centre of the basin and Zanjanroud area. On the other hand, the compliance of the morphology and topographical trends of the basin, as well as the Zanjan River canal and many drainages with the extraction lines with the help of geomorphometric techniques, clearly shows the effectiveness of geomorphometry to evaluate and prove the impact of terraforming on the geomorphology of the basins. Although no destructive earthquake has been reported in the region, But the presence of morphological evidence and the interruption of Quaternary to Holocene deposits indicate the active deformation of the region. Therefore, it seems that the fault systems of the basin have the potential to create earthquakes with a much higher magnitude than what has happened so far, which indicates the necessity of planning based on a detailed study of the faults in the region
Extended Abstract
Introduction
Understanding the geological conditions of each region and basin, along with other influencing factors, has a significant role in understanding the governing processes. Zanjanrud basin stands out as a small local plateau and in a heterogeneous manner with the topographic alignment of the surrounding area. In this research, an attempt was made to evaluate the tectonic effect on the geomorphology of the Zanjanrud basin using remote-sensing and geomorphometric techniques. The main objective of the research was to investigate the morphological pattern of the Zanjanrud bed and its relationship with active fault tectonics.
 
Methodology
In this research, remote sensing and geomorphometric techniques, along with field observations, were main tools of investigating and evaluating the effects of faulting on the geomorphology of Zanjanrud basin. The data used were Sentinel-2, Landsat- 8 & 9, Quick-bird data, SRTM-DEM 90 & 30-meter, and the DEM 10-meter. The data were used to extract geomorphometric indicators and enhancement of the morphotectonic elements and geomorphometric analyzes and evaluation of the effect of faults on the landscape and landforms of Zanjanrud basin. In addition, in this regard, field surveys have been conducted to validate remote sensing and geomorphometric findings and prepare ground truth data for comparison and accuracy evaluation.
Different software (ENVI, SAGA, MicroDEM, ArcGIS, GRASS) are used to geomorphometric analysis of morphometric parameters, extraction of geomorphometric indices and characterization of morphotectonic elements. In this research, by extracting the basic parameters of the earth's surface, the elements and parameters of the topographic surface have been identified and, based on them, the anomalies of the topographic surface have been detected. Neotectonic and faulting are among the most important factors causing anomalies in topographical surfaces.
 
Results and Discussion
In this research, we tried to enhancment of the fault maps and the topographic, hydrological and structural trends of the basin that are used to enhancement and documenting the anomalies of the topographic surface including the effect of faults and fracture systems in the area. The map of hill-shade parameters and indicators, profile and plan curvature, and topographic surface roughness index have clearly enhanced the effect of basin faults. In the meantime, two fault systems have been confirmed in the basin with high certainty. Geomorphological analysis based on high-resolution images, digital elevation models and field observations made it possible to estimate the evolutionary pattern in the form of these active structures. Although the focus of the current research is on Zanjanrud, which almost follows the extension of the Zanjan Fault, but in order to understand the dynamic pattern of faults and their effects on Zanjanrud, neotectonic evidence based on basin geomorphometry has also been discussed.
 
Conclusion
In general, the results of this research are:
- Neotectonic evidences: Examining the neotectonic evidences show that the faults in the region are active faults and have a high potential for seismic activity by cutting Quaternary sediments.
- Deformation of Zanjanrud Basin: This study showed that Zanjanrud Basin has been affected by four main fault systems and several sub-faults with different scales. These changes have forced the formation of mountain, foothills, plains and changing the course of Zanjanrud.
- Tectonic patterns of the basin: Zanjanrud basin is exposed to complex tectonic stress patterns due to its geographical location and location at the meeting points of Alborz (western), Talash and Central Iran morphotectonic units. These tectonic stress patterns include north-south convergent movement in the direction of Arabia-Eurasia. Also, the performance of regional-district-local units has also played a role in the formation of the Zanjanrud basin.
- Zanjan is a fault plain: it seems that the subsidence resulted from the intersection and interaction of two northwest-southeast fault zones and north-south have a role in the formation of the plain. Zanjan. Also, the simultaneous and active action of the faults have caused morphological anomalies in the topographical level in the Zanjan river basin.
- Anomaly of Zanjanrud channel and heterogeneous topography in Zanjan plain and basin: The northern part of Zanjanrud basin has two main lines that continue towards the south. These lines have caused the interruption and displacement of Quaternary sediments on the level of the plain, barracks, beaches and Zanjan river channel.
This research shows that the morphotectonic evidence of Zanjanrud basin indicates the presence of faults and active fracture systems in the region, which has a significant effect on the formation of morphological and topographic anomalies in Zanjanrud basin.
 
Funding
There is no funding support.
 
Authors’ Contribution
All of the authors approved the content of the manuscript and agreed on all aspects of the work.
 
Conflict of Interest
Authors declared no conflict of interest.
 
Acknowledgments
We are grateful to all the scientific consultants of this paper.