جستجوی مقالات مرتبط با کلیدواژه "ژئوئید" در نشریات گروه "زمین شناسی"

Assessment of data uncertainty increases our ability to study and accurate understanding of about real world, because awareness from uncertainty of resources and remove error for improving the obtained results is one of the most important items in the remote sensing science. Since the digital elevation model (DEM) extracted from different sensors and geometry, Therefore selection of the most suitable DEM that provide better ground conditions is the one of the main needs for experts in this field. The aim of this study to vertical accuracy assessment of the ASTER and SRTM digital elevation model compared to the elevation data from topographic maps that prepared by the Iran National Cartographic Center in the 12 city from Khuzestan province. In order to evaluation the accuracy of the data, the Mean Error (ME) index and Root Mean Square Error (RMSE) index are used. The result of evaluation ME index for the cities with topographic map for ASTER and SRTM data showed the value 6.08 and 2.34 meter, respectively. Also, the result of RMSE index for ASTER and SRTM data showed the value 6.94 and 3.46 meter, respectively. Therefore more, the result showed that in most cities of Khuzestan province the DEM derived from SRTM has a higher accuracy than the ASTER digital model; Since the SRTM data have a low uncertainty, Therefore in studies related to the extraction drainage network, drainage density, physiography of the watershed area, runoff or geology, it is suggested that SRTM elevation model be used.

Summary For the present two-dimensional (2-D) lithospheric density-temperature distribution modeling, we have selected a north-south geo-transect cut in east of Iran from the Oman Sea to the Lut block with a length of about 800 km. As the structural domains, investigated in this paper, have mainly been created under the effect of the north-south subduction of the Arabian Oceanic Plate under the Eurasia, thus, most of these structures are approximately perpendicular to this direction. As a result, in order to avoid three-dimensional (3-D) structural effects in our 2D modeling, we have selected a profile perpendicular to the strike, which is roughly the north-south direction.
Introduction In order to avoid interpreting isolated anomaly features being located accidentally on the profile of the geoid, free air and topography data, we average the data within a width of 50 km to both sides of the profile and calculate the variance within this stripe using 5 km long steps along the profile. The resulting standard deviation is plotted as uncertainty bars. Since the lateral resolution of our data is of the order of several kilometers, therefore, we cannot reproduce small‐scale details. The generated model consists of a sedimentary layer, the upper, middle and lower crust and a lithospheric mantle layer. In order to constrain the various thicknesses, the results of previous works carried out in the study region have been used.
Methodology and Approaches Modeling carried out in this research is based on the assumption of local isostatic equilibrium and joint interpretation of gravity, geoid and topography data with temperature-dependent density. Bouguer anomaly data are mainly sensitive to crustal density distribution and decrease proportionally to the squared distance (r) from an object, whereas elevation is very sensitive to changes in density and thickness of the lithospheric mantle and the geoid undulations diminish proportionally to r−1. The data different sensitivity on distance from the object can be a good constraint on modeling lithospheric density-temperature distribution.
Results and Conclusions Because of subducting Arabian plate in Makran subduction zone, thickness of the lithosphere increase from the Oman Sea (90 km) to the Taftan-Bazman volcanic arc, with a maximum thickness (290 km) under the volcanic arc. Based on our modeling results, subduction of the oceanic crust of Arabian plate under the Makran belt starts with a very low dip angle and bends under the Taftan-Bazman volcanic arc with a relatively higher dip. There is a logical correlation between the subducted slab and the seismicity of Makran subduction zone. Because of the low dip subducting slab, there is a long distance between volcanic arc and forearc setting (~450 km). Further to the north, lithospheric thickness is reduced to the ~200 km under the Lut block which is in good agreement with earlier studies. Our integrated modelling approach reveals a crustal configuration with the Moho depth varying from ∼21 km beneath the Oman Sea, and ∼47 km beneath the Taftan-Bazman volcanic arc to about 37 km beneath the Lut block. Across the Makran subduction zone, Moho depth is increasing from the Oman seafloor and Makran forearc setting (~21 km) to the volcanic arc (∼45–50 km). Furthermore, we have found that the oceanic crust is a two layered plate and there is a thick sedimentation there to about 8-9 km.

Geological events and the curiosity of human mind to comprehend these phenomenacompel the researchers to investigate their structures and tectonic evolution. Some keyparameters to better understand these subjects are Moho Depth (the boundary betweencrust and mantle) and also the Lithosphere-Asthenosphere Boundary (LAB). There are methods available which can give us some knowledge about these key parameters such as seismic, magnetotelluric, volcanologic and etc. Each one has advantages and disadvantages. In the seismological method, a period of about six months is needed to be sure that a reasonable quantity and quality of events has been detected to record enough data during the research. The high expense of instruments and lack of access roads in high topography has limited this method to adequately capture the data researchers seek. These problems also exist in the seismic base method. The seismic method is generally expensive. Moreover, this method is nearly blind in lithospheric depth such as LAB.We tried to introduce another method that used potential field data. Our data weretopography and geoid undulation mainly observed by satellites. The method for this studyutilizes some basic concepts such as local isostasy as wel as some basic physical andmathematical rules, relations and equations. Our topography data were from the newlyreleased topography database for all over the world, ETOPO1. The spatial resolution ofthe data were 1 Arc-minute. The geoid undulation was calculated by a spherical harmonicup to order 2159 and degree 2190 from Earth Gravitational Model's 2008 (EGM2008). Toavoid the effects of anomalies deeper than LAB, wavelengths greater than 4000 km wereremoved. There were some advantages to this method such as: the higher speed of thecalculation so that the examination of a big region was possibile at a fraction of the costfor other methods. Modeling was done on a very substantial area in the Northern part ofthe Iranian plateau that included the Northern part of Central Iran, the Alborz Mountainsand the South Caspian Basin.The results showed the evidence of thickening of the crust up to ~55 km underneath the Alborz Mountains. However, many previous researchers concluded no roots there. The other outcome of utilizing this method was thinning the crust and lithosphere underneath the Northern part of Central Iran (36-38 km for the crust and 140 km for the LAB) relative to the surrounding area. Our data reflected a solid correlation with some previous work and geological evidence. Subduction of the south Caspian basin (probable oceanic crust) underneath the Eurasia plate is completely visible; however, this activity was not recognized in Kopet-Dagh.