جستجوی مقالات مرتبط با کلیدواژه « khanmirza plain » در نشریات گروه « جغرافیا »

Khanmirza plain is one of the plains of cold and temperate regions of Iran, with an average rainfall of 500 mm per year and sufficient nutrition in terms of surface resources, the subsidence event is currently happening in it with a rapid trend. In terms of geostructure, Khanmirza plain is located in the folded Zagros zone in the south of the Dana fault, and the presence of piezometers protruding from the soil, as well as the presence of springs, etc., are signs of crustal movement on the surface of this plain. For this purpose, with the aim of evaluating the tectonic activity of the region in creating the phenomenon of subsidence from some geomorphic indices such as basin shape index (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), reverse topography symmetry index (T), integral index Hypsometry (H) of the region's subsidence was studied tectonically. Likewise, the subsidence rate was determined using radar interferometry. Examining these indicators showed that the indicators of basin shape (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), reverse topography symmetry index (T) are active tectonics in the region. Earth construction activities have caused the plain to stretch and become asymmetric on both sides of the main river. Likewise, the results of radar interferometry in the two-year period indicate that parallel to subsidence (at a rate of 9 cm) in some parts of the plain, other parts are facing uplift (at a rate of 21 cm).Collapse and subsidence can be caused by natural geological phenomena such as earthquakes, dissolution of limestone, chalk and salt rocks, melting of ice and compaction of deposits, slow movements of the crust and the release of lava from the solid crust of the earth, or activities human activities such as mining, extracting underground fluids such as underground water, oil or gas (Galloy and Barbie, 2011: 1459). Radar interferometry has been widely used by Earth researchers since the early 1990s (Shirani et al.: 2013). This technique can be used to measure displacements resulting from many phenomena such as earthquakes, landslides and subsidence. In general, there are nearly six hundred plains in Iran, and it is likely that more than half of them are subject to subsidence (Kia Sharifi, 2010: 58).

In order to evaluate the tectonic situation of the region, from topographic maps 1:50000 and geological map 1:100000 to calculate basin shape index (BS), river longitudinal gradient (SL), drainage basin asymmetry (AF), symmetry index Inverted topography (T), hypsometric integral index (H) from (DEM) 30 meters and topographic map were used, which were processed in GIS environment. D-InSAR radar images were used in the period from 2003 to 2005, which were processed in ENVI 5.3 software. Radar interferometry technique

How to calculate the SL river gradient index: The SL index is calculated for the middle point between two flow curves. Symmetry index of transverse topography (T): this index can also specify the state of symmetry and, as a result, the active or inactive state of the region. Drainage basin asymmetry index (AF): The asymmetry index is a method to evaluate the existence of tilts caused by tectonic activities at the scale of the drainage basin. Basin Shape Ratio Index (BS): Basins that have an elongated shape are tectonically active. And the shape of basins that are tectonically inactive tends to be round. Integral Hypsometric Index: Integral Hypsometric is an index that calculates the height of the entire area in relation to the area of the entire area. The values of this index show the transformation stages of the landscape in the erosion cycle. Today, radar interferometry, as a technique that estimates the displacement of the earth's surface with high accuracy and resolution, is a common tool for investigating the change of the earth's surface due to various factors, including land subsidence. In this technique, an interferogram can be prepared using two satellite images. So that by using the interferometric tool, the phases of the return signal from the ground are subtracted from each other in two time-delayed satellite images of the same region to extract changes in the ground surface. The radar interferometry technique uses Sarscape software as one of the powerful tools in the digitization of satellite images to survey the changes in the earth's surface. In this research, 12 Envisat satellite images from the European Space Agency were prepared

 The amount of subsidence calculated from 10 paired images is 9 cm drop in a two-year period, and the amount of elevation obtained from the images was calculated as 21 cm in a two-year period. By comparing these two numbers, it can be concluded that in this basin, the uplift rate is twice as high as the subsidence rate.The obtained values show that in addition to groundwater extraction as one of the main and common causes of subsidence, considering the tectonic factor in areas such as the Khanmirza watershed with high rainfall input is one of the main reasons for its formation.

Land subsidence is one of the environmental hazards caused by various factors, and especially in recent years, it has caused a lot of damage to human societies. The Khanmirza plain aquifer has also faced this phenomenon in recent years. The creation of wide gaps and cracks on the surface of the plain and the release of gas from them makes the issue of subsidence important. For this reason, the present study tries to monitor and measure the amount of land subsidence in Khanmirza plain, and evaluate and analyze its relationship with the withdrawal of excess from underground water sources. For this purpose, in order to investigate the changes in the underground water level during 10 years and in two different time frames from the IDW geostatistics model and to estimate the subsidence of the land surface using the differential radar interferometric method and from the Sentinel-1A radar images during 5 years and in Three different time periods were used. The results of the research indicate that displacement of the earth's surface in different time periods is different and does not have a constant trend, while the trend of the drop of the underground water level has been increasing in the whole time period. Accordingly, according to the results of the research, there is no significant relationship between the indiscriminate extraction of underground water sources and the subsidence areas in Khanmirza plain.

Usually environmental science and geography researcher use OLS model for variable spatial relations analyzing. This model has some lacks and shortagea in spatial outcome especially in local scale. In recent years, GWR model are used by some scientists for analyzing the relation of spatial variables in local scale. In this article, for analyzing and comparison of these models, land use change (as dependent variable) are assessed in relation with drawdown and withdrawal of groundwater resources (as independent variable) in years of 2001-2011 in Khanmirza Plain (Chaharmahal va bakhtiari province). In order to study the models efficiency, the Standardized residual variation's coefficient, Spatial Local dependencies, Morn’s Index, Corrected Akaike Information Criterion and Local coefficient of determinationwere used. Result indicate that based on Standardized residual coefficient of variation, GWR model has better ability to adopt data on variables respect to OLS. The findings of the research showed that based on the standardized coefficient of variations, GWR model has the ability to adapt data than OLS. Also, based on the results of the explanation coefficient on the variables of the research, GWR model creates a favorable local fit between regression and sample points. Based on Morrow index, GWR pattern represents the least similarity of the amount and location in the adjacent positions of the data samples and prows the performance of GWR model in providing spatial outputs relative to the OLS pattern