fatemeh kiaroostami

Identification of active tectonics in an area and its effects on the morphology of landforms is one of the topics that has always been of interest to geomorphologists. Waterways are among the features that flow a wide range of landforms. These features are sensitive to lithological or tectonic changes and react quickly to these changes. The riverbed has been affected by these anomalies and the effects of these anomalies can be studied in the longitudinal profile of the river. In other words, waterways are active tectonic markers that give us information about the characteristics of a landform.

The study area is located in the south of the Eastern Alborz Mountains and is known as the Siah-Kuh Heights. This ridge consists of a set of dolomitic and sandstone rocks of Sibzar and Padha Formation and Damghan fault passes along it. The main purpose of this study is to investigate the morphological and tectonic structure of Siah-Kuh using steepness and concavity parameters based on the anomalies of longitudinal profiles of the rivers based on the uplift and subsidence axes. In order to calculate the rate of steepness and concavity of longitudinal profiles, the stream power low formula is used based on the two main parameters of drainage area and slope of river. This formula is based on a logarithmic plot of the slope and drainage area for which the appropriate regression line is determined. In this regression relation, the slope of the line is the concavity parameter and the intercept is steepness parameters.

The extent of the Siah-Kuh heights among a series of young Quaternary sediments at a distance of 4 km from the main mountain front, the structure of the Siah-Kuh is similar to Foreberg forms. Damghan fault in this area has led to the intersection of Quaternary sedimentary strata related to the surrounding alluvial fans and by creating a transtensional position in the form of a set of trapped traps, the Siah-Kuh Foreberg has appeared as a restraining bend on the surface Which has led to the elevation of the central part and the relative subsidence of both sides of this structure. The eastern part of the Siah-Kuh Foreberg appears to have been covered by Neogene and Quaternary sediments. Its remnants have appeared in the form of deep gorges on the surface. One of the rivers flows on the main surface of Foreberg and the other flows in the drained or buried part of Foreberg. Both rivers have several knick points in their flow path, which are taken from the location of faults and lithological differences of the riverbed. The values of the steepness parameter for the main river and the gully show high values so that the value of this parameter is 121.4 for the main river and 119.96 for the gorges. In contrast, the depression parameter rate in both rivers shows very low and even negative values. (Main river: -0.18 and gorges river: -0.92). Since the sharpness parameter is directly related to the tectonic processes; It can be said that the values of this parameter in both rivers indicate the effect of active tectonics at the level of Foreberg.

The studies performed on the study area show that the two factors of active tectonics and lithology have a great impact on the morphological structure of Siah-Kuh Foreberg. Also, factors related to sedimentary flows originating from the uplands of the area have been effective in changing these landforms in the form of burial. Also, the results showed that the use of the method based on longitudinal profile anomalies of the river in the form of steepness and concavity parameters has an effective role in identifying erosion and subsidence axes related to tectonic situation of features in relation to their topographic changes. Slight difference in the amount of steepness parameter in gorges compared to the river on the main surface of Foreberg, especially in the first trends of both rivers, which show high values of steepness parameter with a small difference (1.44), Indicates the existence of an uplift axis in this area, which somewhat confirms the burial of a structure similar to the Siah-Kuh Foreberg under sediments.

Damghan area has been considered by earth scientists due to the existence of numerous active faults. These faults with slow and progressive movements have led to changes in the shape of landforms in the area. Even during the history, the activity of these faults led to major earthquakes such as Qumis earthquake in 856 A.D. This earthquake led to the complete destruction of Qumis province in present-day Damghan. Researchers in the area, including Hollingsworth et al 2010., have concluded that major faults in the area, such as the Astaneh and North Damghan faults, have ruptured during the Qumis earthquake. The changes in landforms and high potential of faults in creating seismic events indicate their continuous activity during Quaternary up to now. To study these changes, we need those features that are sensitive to tectonic and erosive events. Rivers are one of these features that react quickly to active tectonic and erosion changes. The main purpose of this study is investigation of the changes in landforms using anomalies in stream orders. Because there is a hypothesis that claims tectonic and erosive changes lead to irregularity in Strahler orders of streams. In this study we use isobase and differential map method to investigate this hypothesis.

Sensitivity of drainage network to tectonic processes and geological contradictions leads to changes and irregularities in river orders. Isobase maps are extracted from information about the spatial classification of rivers and their elevation information in the environment. In fact, these maps show the relationship between the pattern of waterways and the topography of landscapes. Streams with the same Strahler order are formed by the same geological events, and most likely the same order is the same age. We can draw iso base maps for different stream orders. Early orders (1-3) are mostly more sensitive to tectonic events. These early orders due to flow along seams and fault gaps are representative of neotectonic. Rugged structures in the lithology of the region can limit the evolution and development of the early orders, and therefore in these areas the values of the isobase map increase. But isobase map of evolved orders can represent longer periods, such as the Quaternary or Pleistocene. Because evolved orders are formed over longer periods and are able to show older tectonic and erosive events. Differential maps are obtained from the difference in height between the maps of the evolved orders and the present day topography map.

Examination of the isobase map of the primary orders show that most of the values related to the map can be seen in the west and north of the region. These areas are based on mountainous structures. The high values of the isobase map in these areas indicate that the northern and western parts, affected by neotectonic activities and the development of fault gap and seams, have more primary orders of rivers. Because most of these primary orders are formed and developed along these levels of weakness. Resistant lithology of the area has also prevented the development of these orders. The highest value of them is 3830-2312 meters. The differential map prepared from the study area shows a wide range of positive values indicating uplift and negative values indicating subsidence. By examining these values, we can understand the features related to tectonics and geomorphology of various landforms in the region. The highest values of 1191 to 800 meters are related to the high mountain structures of Eastern Alborz in the north and west of the region. The decrease in the value of the differential map indicates the effect of tectonic subsidence on the morphological landforms of the region. The Astaneh pull apart basin in the western part of the region shows the amount of subsidence between -4 to -1 meters. Also, the southern playa of Damghan in the form of a concave foreland basin affected by active faults in the region shows negative values, which indicates the existence of a submerged basin with high sedimentation potential.

Studies conducted on the area show that the two factors including active tectonic and lithology have a great impact on the morphological structures and landforms of the area. The results of isobase map and the differential map show and confirm this issue. The methods used in this study to investigate the tectonic activity of the faults in the area indicate their activity during the Quaternary. These faults have different mechanisms of thrust and streak slip which in some areas also have transtensional and transpressional position; they have created a collection of uplifted or concave landforms in Damghan area. The spatial relationship between different values from north to south in the prepared maps indicates the creation of an equivalent states between topographic growth and its destruction in lower altitudes. Based on the studies, we confirm that the preparation of isobase and differential maps can be a suitable method for studying and examining morphological structures. Also studies related to differential map show anomalies in drainage networks and uplift processes associated with active Quaternary landforms can be quantified by these maps. Using baseline and differential maps is one of the appropriate methods to study the Plio-Quaternary tectonics in an area. This study confirms the work of previous researchers based on the available information and documents related to the study area.

The identification and analysis of the active tectonic or denudation processes through the analysis of the deformation and landform changes consist one of the fundamental objectives of the tectonic geomorphological studies. Rivers are among the groups of geomorphologic elements that flow on a wide range of different landforms and can reveal the critical relationships among uplift, lithology, and denudation of heights. With regard to the evolution of landforms, this group of information and the relations between them are preserved by the bedrock properties. River Incision is the primary mechanism by which landscapes adapt to climate change and tectonic forces. Among the many factors that affect the Incision rate, the distribution of slope and steepness of water channels can be systematically effective. The main purpose of this study is to investigate the sequence of mountainous and foothills landforms in Damghan region using slope changes and erosion-incision reaction of rivers on the surface of these landforms as one of the key factors in landscape evolution.

There are many models for calculating the river incision rate, but the most widely used is the SPIM model, which is presented in the form of the following equation:I=K*A^m*S^nThe SPIM model is based on simple geometric parameters, such as the slope and area of the drainage basin extracted from the DEM elevation map. Some parameters are related to energy considerations, such as the rate of energy consumption in the channel bed and ridges, in which case; m: 0.5 and n: 1 are used as experimental constants in the formula.In order to calculate the values of this index and prepare a river incision map, first the whole study area was divided into 64 sub-basins so that the resulting section values are suitable for surface interpolation. In the next step, the values of effective indicators in the SPIM formula including river slope, drainage surface area and erosion efficiency were calculated for each of the sub-basins. To calculate the erosion efficiency index, first the steepness values of the rivers of each basin were calculated from the formula of stream power incision, based on power regression, in the form of the following equation.S=K_s A^(-θ)In the above formula Ɵ is the amount of concavity and KSN is the amount of steepness.After obtaining the steepness values of rivers in each of the 64 catchments, the erosion efficiency relationship was used as follows:U=〖ksn〗^n*KU is actually the rate of elevation or change in altitude of the area relative to the base level, which was calculated using the radar interfrometry method to determine the amount of vertical displacements in the area.In order to prepare and analyze the slope and incision rate of rivers in Damghan region, and to convert point values into raster levels containing value, the inverse distance weighted interpolation method or IDW was used.

Comparison of longitudinal profiles taken from the slope map and incision rate of Damghan region shows the close relationship between these two parameters; Both of these parameters together play an important role in analyzing the tectonic status of the areas. In such a way that in examining the condition of the longitudinal profiles of the region from north to south, there are prominent features such as mountain belts or foreberg shapes; The slope rate and incision rate of the river increase and in front of where there are depression constructions such aspull apart basins or the end parts of longitudinal profiles that are based on alluvial plains, the slope rate and the following incision rate of the river decreases.Therefore, the analysis of longitudinal profiles taken from the slope map and incision rate of rivers in Damghan region can be effective in identifying and analyzing the effect of active fault mechanisms on the sequence of landforms in the region. the areas that have mainly high slope and incision rate of the river and are shown prominently in the longitudinal profile, represent the performance of faults in the form of transpressional, which leads to the formation of elevated landforms. In contrast, the concave areas in the longitudinal profile of the slope and incision of the rivers in the region are mainly representative of the areas where the gentle slope has led to a reduction in the slope of river systems and thus reduced river incision capacity.these areas are either mainly based on flat lands which are in the southern part of mountain structure in form of alluvial sediments or they are collapsed structures due to transtentional motion of faults such as Astaneh pull-apart basin.

The activity of faults with different mechanisms causes the uplift or subsidence of landforms to form a series of successive landforms in an active tectonic environment. The rise and fall of these structures have led to an increase or decrease in their slope which will effect on the waterway systems that flow on these landforms. Wherever the fault mechanism leads to an increase in the height and elevation of the landforms, the slope of the river increases and as a result the incision power of the river increases. From the analysis of longitudinal profiles taken from the slope map and the incision of the river, it can be concluded that this method is very useful in identifying the sequence of landforms affected by tectonic processes. In a way, by examining the process of changing these longitudinal profiles, we can understand how active faults function in shaping landforms in compressive or tensile form. Wherever the slope of the waterway is high and the incision rate of the river is high, it indicates the existence of a elevated axis. This landform can be a mountain ridge or even elevated forms among alluvial sediments.wherever the slope and incision rate of channel show low values, it can indicate the existence of a concave tectonic basin.

Landforms and their response to environmental changes is one of the most interested topics among geomorphologists. One of the landforms that is most affected by tectonic and erosion processes is the rivers. Rivers respond to tectonic processes that increase the height of landscapes and erosion processes that try to reduce the height of landforms. This reaction can be well studied by analyzing the longitudinal profile of the rivers. One of the effective parameters in the study of tectonic and erosional status of regions is steepness and concavity. These parameters can be examined in the form of Stream Power Law (SPL). This function is related to incision power of streams.This relationship in the form of the linkage between slope and drainage area of the river in a logarithmic plot based on power regression, extracts the values of two parameters, the steepness and the concavity of the channel. In fact experimental studies by other researchers have shown that there is a direct relationship between rivers steepness and concavity with tectonic – erosive processes in the regions. It generally accepted that steep landscape are associated with areas of high uplift rate and active tectonic. Rivers system are well adopted to tectonic processes to provide useful information about the rate of uplift in landforms. The steepness of rivers which depends on the declivity of channels is fraction of uplift rate. So we expect that if the amount of the steepness in the longitudinal profile of the river is low, the uplift rate is slight too and if the steepness is high, the uplift rate is intense too. Concavity index usually depends on bed material. But erosion efficiency has direct connection with incision power law and its steepness. But weakness of bed material especially alluvial can increase rate of erosion efficiency in channels. Erosion efficiency is the volume of sediment that is completely removed from the environment after erosion. Erosion efficiency is a function of sedimentary flux. This parameter can be directly related to the tectonic processes and characteristics of the bedrock. If tectonic processes lead to an increase in the height of the landforms, it can increase orographic precipitation in mountainous areas, and it can lead to increasing sedimentary flux, then erosion efficiency also increases. The main purpose of this study is to analysis the effect of active tectonic and erosion on equilibrium profile of the main rivers of the Damghan Mountain based on the Stream Power Law. These steepness and concavity parameters are influenced by set of lithological, geological, topographic and erosion factors. All of these factors are effective in location of knick points of rivers and are able to provide useful information about the geological and erosion status of the area

In order to investigate the power incision law, the DEM map in 30m resolution was used to extract the channels. For extracting the rivers, the D8 algorithm method was used to calculate the flow direction. In this method, the flow path of each pixel that fall on the lower pixel with a lower slope was calculated and the flow directions was determined. In this regard, we first need to create a DEM map with the least inconsistency. This method focuses on extracting central flows in valleys and reducing parallel flows. After extracting the channels, their slope-area logarithmic diagram were plotted. The regression line considered for the logarithmic plot is the power regression, which is the relation of the river incision power. In this regression, the slope of the regression line is concavity and the intercept of line is steepness. To obtain information about lithological features of the area that are effective in analyzing the concavity and steepness parameters, the geological map of Damghan and Shahrud was used. The study area is part of the mountain structure of Eastern Alborz and has several active faults. North Damghan Mountain is located on the southern side of eastern Alborz between 36。14'0.3" to 36。18' 82" and 55。00' 26" to 53。59' 56" in north of Iran plateau. There are different outcrops of lithostratigraphic formations from Precambrian to Quaternary in this area. Geologically speaking, the study area is composed of set of over thrust blocks and nappes. The thrust faults and nappes within piggy back style have pushed eastern Alborz stratigraphy sequences on each other. The folds in the region have a strong connection to thrust structures and nappes. These folds are of different types and sizes but most of them are inclined and recumbent because of widespread compressive component in eastern Alborz.

The three main rivers of the region, CheshmehAli, Astaneh and Tepal, were studied. All three rivers flow on the colluvium bed in the upstream and alluvial bed in the downstream. And all three affected by faults in some areas. Some such as CheshmehAli River in the southern part, has flowed into a fault valley. The activity of faults along the rivers, both in the resistance and alluvial parts has led to uplift of the rivers. These effects are seen in the high values of steepness index and low values of concavity index. The increase in the stream incision is seen in both the upper and lower section of the rivers due to the activity of faults in the region. But the steepness is higher in the upstream which is made of colluvium sediments. While in the downstream due to weakness of alluvial sediments the rate of erosion efficiency is higher. Therefore the change in the rate of steepness, concavity and erosion efficiency, in addition to active tectonic, is strongly affected by the bedrock of channels. Each rivers that is most faulted also has higher values of the steepness index. CheshmehAli River, part of which is located completely in the faulted valley, has the highest rate of steepness compared to other rivers. The Astaneh River has been affected by the Astaneh fault in several parts, and the fault has led to the uplift of the river by cutting off the Quaternary sediments. The high values of steepness parameter in this river confirm existence of active tectonic. The Tepal River in its upper part shows high values of steepness parameter, but in the downstream part where the river flows on agricultural lands, the rate of erosion efficiency has increased and in contrast the rate of steepness parameter has decreased. This is due to human activities that have caused the rate of erosion to exceed the rate of tectonic processes. Therefore, human activities are able to transform the relationships between internal and external processes that are effective in changing landforms.

The results show that reaching the equilibrium profile in each river depends on a set of factors include erosion, tectonic and lithology. Fault in the channel path leads to an increase in the height and slope of the river channel and erosion accurse in response to this change. Tectonic processes increase the incision capacity of rivers as a result of increasing the slope of the channel, which increase the volume of sediments produced in the river. Of course, like that Tepal River, we must consider the role of human activities in increasing the rate of erosion efficiency. Key Words: Eastern Alborz, Damghan, Active Tectonic, Morphotectonic, SPL Model.

Tectonic Geomorphology is one of the Emergent Disciplinesin Geosciences; Region is very sensitive to Tectonic Process such as Faulting, One evidence of the Areasensitivityof the active tectonic processes,the watershed Shape is affected by it.Active Tectonic Basin due to Uplift is Oblong and Inactive Tectonic Basin due to Erosion is Circular.Some tectonic indicators can give researchers information about the shape of the basin.Including indicators of Basin Shape Ratio, Basin Shape and Factor, Compactness, Circular Ratio and Elongation Ratio.

Position of the Iranian plateau in the plate of Arabic, African and Eurasian Has great influence on the movements of these plates with continental crust Shelf As a result, the country has become a most dangerous and volatile environmentIn the tectonically.Hence, due to such risks is critical. The remarkable thing is that the long-term effect of active tectonic regions Before examining the hazardous occurrence and tectonic activity areas noted. One of the effects of active tectonics in the drainage basin scale Effect on the shape of the basin Thus, the area affected by tectonic activity and young because Uplift they tend to stretch And tectonically active basins lacking As a result, they become round wear. In this study, using the profiles of the basin shape ratio, shape factor, form factor, Compactness, Circular Ratio Elongation Ratio amount of Neotectonic activity in the Roodak basin Located in the north of Tehran were studied And validity of these indicators next to Common index Basin Shape ratio was measured. Results for sub watershed studies on Amameh, Garmabdar and Meygoon and Ahar indicates that although this indices Fractional Basin shape ratio sync, the study of tectonic activity watershed not used But can detect the influence of neotectonicOn watershed Drawn on the basis of active tectonic basins Be examined in conjunction with other Neotectonic indices. If the criteria strain Amameh sub basin to the Garmabdar sub basin not stretch well represented. 

In this study, Calculating of Indices based on the shape of the basin, Confirms the active tectonics theory Based on Active Tectonic in Oblong BasinsVersus Inactive Tectonic in Circular Basins. This indicator is shown as well.In this study also, the Highest Value of Shape Factor, Compactness and Basin Shape Ratio Indices and Lowest Value of Form Factor, Circular Ratio and Elongation Ratios Owned Amameh Basin that indicate Oblong shape of Amameh Sub basin. Basin Shape Amameh also confirms this subject; Versusthe opposite of this position for Garmabdar Basin There Are. Garmabdar Basin Shape Confirms the existence of circular shape.

There is evidence of numerous works, such as broken stones on steep walls,Not been sedimentary, tectonic springs and oases such as Ahar and Amameh, Traces and fractures caused by faulting in pieces of Rocks With known faults rooted in the Central AlborzAnd many others active tectonics confirm in the Basin Roodak. Obviously, this movement influence on the Basin Shape. The results show that the indicators used in this Study Except Common indicators of Basin Shape Although the as yet Have not been used to estimate the active tectonics; Can be used for this purpose.But Maximum performance for basins that have different shapes to each other.For Example Amameh and Garmabdar Basins. About The basins are similar to each other, This Indices show Different Value. For Example Meygoon and Ahar Basins That Based on Some Indices Meygoon has Maximum number of Elongation and Based on Some Other Indices Ahar Basin Has Maximum number of Elongation. However, based on these indicators every four basins are tectonically active. But with different intensities in Those Shapeaffected. This is due to the many fault lines in the area is clear. Hence the Researcher Can Use This Indices Next to Other Indices for calculating Active Tectonic in Various Region.

To evaluate the impact of neotectonic on the BasinsInitially in the form of research libraryattempted to evaluate the effectiveness of the basin of tectonic processes Given that there are numerous faults in the area mentioned in various sources, this is a definite influence.In order to investigate further in order to find evidence of active tectonics in the regionField studies were conducted in the basin.Then, using a 2.5-meter resolution satellite imagery in Kartosat  Roodak mountainous watershed boundary identified.And then through wms9.1 software and Arcgis10.0 DEM resolution of 10 m the study areaBasin and its Sub basin and its drainage Networkwas extracted.Then, using indicators of Basin Shape Neotectonic activity in the catchment area of each sub Basin Roodak was investigated.