Identification of possible new fault based on remote sensing in North West Iran

Introduction
The northwestern region of Iran is located on the Alpine-Himalayan orogenic belt, in an area between the South Caspian, the South Caucasus Orogeny, the Eastern Anatolia Plateau and the Northern Zagros, and is affected by the movements caused by the convergence of the Arabian and Eurasian Plates. The study area in this research is located in the Northwestern Iran and includes the provinces of East Azerbaijan, West Azerbaijan, Ardabil and Zanjan. One of the most important structures in this area is the North Tabriz fault, Aras, Ardabil-Miyaneh and Astara faults, which have controlled the geology of the region. North Tabriz fault is one of the most important structures in the northwestern region of Iran, which has controlled the geology and tectonics of the region. These faults have played an important role in the seismicity of this region and have caused major earthquakes in the history of this land. It is also very important to identify the origin of named faults and lineaments and their importance in future construction and reinforcement of structures. Therefore, detection of the pattern of distribution and spatial epicenter of earthquakes, and Lineation in GIS, help to relocated the faults and revealed the new faults.
Tectonics
There are many faults with different trends in the northwestern region of Iran, and the important and active faults known in this region, include the North Tabriz Fault, Aras Fault, Mishu Fault, Salmas Fault, Urmia Fault, Astara-Ardabil Fault, and Mianeh-Ardabil Fault (Zamani, G. and Masson, 2014; Zamani G., 2017). These faults, which have been identified by various researchers and some of them have been introduced, control the major structure and tectonics of this region and also play an important role in the seismicity of this region and have caused major earthquakes in the history of this land. Some unknown earthquakes have also occurred without any connection to a specific fault, and it is very important to identify their origin and consider their importance in civil construction and structural reinforcement in the future. For example, the North Tabriz fault, with at least 16 historical earthquakes, is considered an active seismic fault in the region. In this regard, the present study has attempted to identify such structures using remote sensing methods. The methods used in this study include using Landsat images, using DEM images, applying geometric and spatial correction to the images, image segmentation, and applying appropriate filtering.
Materials and Methods
Considering that many fault lineation in the North-West of Iran have not been identified and studied so far, or parts of them are hidden, therefore, in this research, an attempt has been made to first prepare a map of the known faults drawn from the different sources. Then by examining them and remote sensing studies, the unknown important and effective fault lineation in the Northwestern Iran should be identified and introduced. The data used for this research include Geological, Tectonic and seismic maps of the of Iran. After preparing information layers from the mentioned maps and referencing them to the ground, first the faults related to different maps were identified and unified, then the location of all the faults due to the non-observance of the grid and the global coordinate system in most of the maps that have been Now they have been published, from the point of view of the location of the faults, the images with a spatial resolution of 15 meters were corrected. In this connection, in this research, the identification of structures has been carried out with the use of Remote Sensing. Remote sensing can be used as a method to reveal geological Lineaments by using different digital processing methods on satellite images, important information can be revealed. The techniques used in this project are: combining color images (RGB), performance filters and using DEM images. By examining the faults in the reference layer using the images and filters used (Gussian, Laplacian and Sobel). In addition to the use of satellite images and the combination of different bands, in order to identify the main location of the faults and their spatial correction, defined filters (Laplacian, Sobel and Gusssian) were used to identify the lineaments or highlight the edges. Extracting lineaments from satellite images can be done in three ways: analog (manual), digital (automatic), and semi-automatic (combination of two methods), each of which has its own advantages and disadvantages. Based on the sensitivity of the project and the knowledge of the study area, the lineaments have been separated by analog (manual) method. After correcting the faults extracted from different sources, the new lineaments were extracted from satellite images. For this purpose, first, all the corrected faults in the area were implemented on satellite images to identify the dominant trend of existing faults, areas with fewer faults, and expected diagonal fractures and areas without such fractures, in order to extract the lineaments from these areas. There is a lot of morphological and structural evidence in the identification and isolation of fault lineaments on the earth's surface, including fault detection signs such as linearities, mountain fronts, abrupt interruption of elevations, subsidence intakes, etc. The existence of above ground and subsurface, elongation of strata, seismicity, bending occurred in the process of the axis of folds or along the alignment and displacement of layers, and sudden changes in sedimentary facies in the region. Considering the aforementioned evidences and remote sensing studies and the processing done on satellite images such as the analysis of shadow-highlight images, filtering, etc. New lineaments were extracted in these areas. It was found that each of the faults extracted from different maps are located in different positions and sometimes it is observed that the faults cross the boundaries. In the other cases in some of the geological maps one could see that faults are on the virtues of the mountains. The integration of information and data related to the improvement of remote sensing images and geological maps, tectonic earthquakes significantly helped in the analysis and processing of the lineaments. In this research a lot of these errors have corrected and renew the design of the fault maps in the North-West of Iran.
 
Results and Discussion
In order to extract new fault lines, various evidences have been used, among them are shifting of layers, lithology change, stretching of strata, and remote sensing signs.   The results obtained from this analysis, the spatial correction of the faults extracted from the maps that reduced from various sources which were located in different positions were drawn at the exact location using satellite images, hidden faults and new lineaments with the help of Landsat 8 images. Also fault detection signs were identified in the studied area and thy help about 38 lineaments have been identified in the entire study area. Mainly these faults have East-West and North-East and South-West trend that was for the first time have identified and introduced. The new lineaments identified in the study area have been extracted based on evidence and external signs of fault detection and using satellite images and existing filters, so calling a lineament as a fault, they require identifying the field signs for fault detection, including fault surfaces, fault slickensides, crash on it, etc., therefore, in this research, the name of the lineation is used for them.
 
Conclusion
1-Integration of data related to image enhancement by remote sensing method and geological maps and seismiotectonics has significantly helped in the analysis and processing of lineaments.
2-As a result of these studies, 38 lineaments have been revealed as new lineaments in the northwest region of Iran, and the dominant trend of most of the lineaments is northeast-southwest and east-west, while these 
lineaments were not displayed on the geological maps prepared by the Geological Survey of Iran.
3- Detailed studies of new lineaments and fault signs such as layer displacement, displacement of streams, lithological changes in linear growth of plants, elongation of strata, etc. has led to the identification of 21 new faults out of 38 lineaments in the region.
4- The intersecting lineaments with the existing faults and the almost west-east trend are in line with the trends mentioned by Nogol Sadat (1978) and show a close trend with the basement faults mentioned by him.
5- New lineaments identified in the area based on external evidence and signs of fault detection and using satellite images and existing filters have been extracted, so naming a lineament as a fault requires identifying field signs to identify faults, including fault surfaces, fault mirrors, slips on it, etc. Therefore, in this study, the name of lineament has been used for them.
6- The existence of a lineament on the ground is never a definitive indication of the existence of a fault, and also the certainty of the existence of a fault on the ground does not indicate its exact location, because in some cases, despite the sign or effect of the fault on the ground, the fault itself is located at a distance from this effect. Therefore, in the continuation of this study, it is necessary to scrutinize the lineaments identified by field studies in terms of mechanism and also in terms of location and then introduce them as faults.