Geophysics
zahra hajeb; zahra mousavi; zohreh masoumi; Abolfazl Rezaei
Abstract
The arid and semi-arid climate with a low rainfall along with the population growth has been lead to overexertion from groundwater resources over recent two decades in Iran. This over-extraction has been led to the significant groundwater depletion and water level decline in most parts of Iran as well ...
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The arid and semi-arid climate with a low rainfall along with the population growth has been lead to overexertion from groundwater resources over recent two decades in Iran. This over-extraction has been led to the significant groundwater depletion and water level decline in most parts of Iran as well as to the significant land subsidence in many aquifers throughout Iran. In this study, we investigated the subsidence occurred over the Jafarabad and Qanavat in Qom plain using the radar interferometry technique in conjunction with hydrogeological measurements. We used ENVISAT ASAR images from 2003 to 2010, in descending orbits to produce interferograms. Once all interferograms are corrected from topographic and flatten phase, we obtain the mean velocity map of the Qom plain region based on SBAS time series analysis method. The mean velocity map reveals 35 and 28 mm/yr of going away deformation in the line of sight direction in Jafarabad plain and Qanvat plain, respectively. Zoning map of subsidence resulted from the InSAR analysis in conjunction with the water level measurements and the thickness of fine-grained sediments (clay and silt) across the aquifers indicated that the maximum subsidence occurred in the places that not only have a higher water level decline but also have the thicker thicknesses of fine-grained sediments. This work clearly highlights the influences of mismanagement of water resources and over-extraction of groundwater in the arid areas.
M. Talebian; M. Ghorashi; E. Kosari
Abstract
On 1-12 December 2017 three earthquakes (Mw 5.9 -6.1) shake Hojedk region in Kerman province. We used satellite images, radar interferometry and field investigation to examine the sourceprocesses of these earthquakes in south–central Iran. The epicenter of first two events located near northern ...
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On 1-12 December 2017 three earthquakes (Mw 5.9 -6.1) shake Hojedk region in Kerman province. We used satellite images, radar interferometry and field investigation to examine the sourceprocesses of these earthquakes in south–central Iran. The epicenter of first two events located near northern boundary of the Miankuh, a major topographic feature of the region. No surface rupture has been seen with these events and InSAR results show semi symmetric uplift of the region. Therefore, two scenarios of faulting with dip to the SW or NE are possible. Epicenter of the third event located further north within the alluvial plane. Evidence for coseismic surface rupture associated with this event was first observed on Sentinel satellite image and InSAR analysis. It was then confirmed by field investigation. The event produced a coseismic scarps with more than 1 m vertical displacement over a total distance of∼6 km, along a fault with reverse mechanism and dip to the SW. Any signs of earlier coseismic ruptures along this fault had been obliterated by the time of the 2017 earthquake, probably by occasional flash floods, so that the fault could not been identified beforehand. However, there is evidence of young alluvial offsets further to the NW along strike of the fault, suggesting existence of active structures in the region. Reactivation of blind faults have caused other major earthquakes such as 1978 Mw 7.4 Tabas, 2003 Mw 6.6 Bam, and 2017 Mw 7.3 Sarpol Zahab earthquakes in the past. The Hojedk earthquakes remind us about importance of recognizing and studying blind faults, especially if they are close to population centers.
M. Arjomandi; A. Saremi; A. P. Sarraf; H. Sedghi; M. Roustaei
Abstract
Groundwater modeling, land subsidence hazards and proper management of groundwater resources of the alluvial aquifer in the district 19 of Tehran, south of Tehran Plain need precise estimation of aquifer hydraulic parameters. Besides, traditional techniques and usual graphical methods have been approximate, ...
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Groundwater modeling, land subsidence hazards and proper management of groundwater resources of the alluvial aquifer in the district 19 of Tehran, south of Tehran Plain need precise estimation of aquifer hydraulic parameters. Besides, traditional techniques and usual graphical methods have been approximate, expensive and time-consuming. In this paper, ten sets of aquifer test data were selected; moreover, these data were recorded in a well located in district 19 of Tehran, southwest of Tehran Plain during five years (2008 to 2012). For solving the previous methods’ problems, three computer codes have been developed to optimize aquifer parameters using three optimization approaches on the other hand, two kinds of genetic algorithms and a multi-elitist particle swarm optimization (MEPSO) which avoid getting stuck in local optima and save time. The efficacy and efficiency of the developed codes have been examined using ten sets of aquifer test data of a confined aquifer, and then their results have been compared with the results obtained by the graphical approach using AquiferTest software. Based on the fitness function, i.e. sum of square errors, the MEPSO and the GAs in descending order are more reliable for estimating the parameters contrast with the graphical method. Furthermore, the sensitivity analysis of the parameters during the performance of the optimization approaches has authenticated that the results obtained are enough precise and reliable. Then an equation has been presented according to the amounts of hydraulic conductivity which have been obtained using MEPSO during the years and the amounts of land subsidence rates which have been obtained using geodetic measurement methods to predict the amounts of land subsidence rates through the time when the amount of hydraulic conductivity will reach to Ultimately, based on the equation, after 30 years the amount of hydraulic conductivity will reach to and the total amount of land subsidence will be 0.5213 m from 2008 to 2038 . Moreover, land subsidence rates’ data obtained from interferometry synthetic aperture radar (InSAR) have confirmed the accuracy of the equations.
Mojtaba Arjomandi; Ali Saremi; Amir Pouya Sarraf; Hossien Sedghi; Mahasa Roustaei
Abstract
During recent years, groundwater exploitation and thereby decreasing hydraulic head in the compressible sedimentary aquifer which is placed in the district 19 of Tehran have been caused noticeable land subsidence. The land subsidence has been damaging the infrastructures which have been being built in ...
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During recent years, groundwater exploitation and thereby decreasing hydraulic head in the compressible sedimentary aquifer which is placed in the district 19 of Tehran have been caused noticeable land subsidence. The land subsidence has been damaging the infrastructures which have been being built in the south of Tehran Basin, especially in the district 19 of Tehran. A finite-difference groundwater flow model (MODFLOW) and a synthetic aperture radar (SAR) method have been used to estimate and predict the rate of land subsidence in this area, and help hydrogeologists manage the vital groundwater resource correctly. The data have been imported into the model, and the change of the amount of land subsidence and head have been obtained for 39 years. Then the available radar images have been processed. Afterwards, the head calibration and subsidence calibration have been done. The results of the calibrations confirmed the accuracy of the results obtained by the model. Finally, this study suggests that 118 mm of land subsidence and an 11.6 m piezometric head decline are likely to occur from 2014 until 2043.
M Amighpey; B Vosooghi; M Motagh
Abstract
An earthquake with the magnitude of 5.9 ML shocked the Qeshm island located in the Persian Gulf on 27 November, 2005 at 13:53:22 local time. The earthquake occurred due to the reactivation of a NE-SW fault with a major reverse mechanism accompanied by a minor strike-slip component. Another earthquake ...
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An earthquake with the magnitude of 5.9 ML shocked the Qeshm island located in the Persian Gulf on 27 November, 2005 at 13:53:22 local time. The earthquake occurred due to the reactivation of a NE-SW fault with a major reverse mechanism accompanied by a minor strike-slip component. Another earthquake of 5.5 MW occurred on the same day at ca. 20:00 local time. The interesting feature of this earthquake is that the calculated mechanism for its strongest aftershock, which occurred ca. 6 hours after the main-shock, was a strike-slip mechanism that is completely different from the pure reverse mechanism for the main-shock. This study uses inversion of InSAR observation of earth surface displacement field boundary values to solve parameters of these 2 earthquakes. The results show activation of southern part of the Qeshm fault caused by the first earthquake along 7 km of its length. This event induced the second earthquake by activation of another strike-slip fault which is parallel to the Gavarzin anticline. Estimated slip was 96 cm for the first earthquake and 9 cm for the second one. Based on the estimated parameters of the these 2 earthquakes, the maximum displacement induced by the first earthquake was 6.7 cm in west, 4.6 cm in south and 16.4 cm in vertical directions on the earth surface. The maximum displacement of the second earthquake in west, south and vertical directions were 1.3, 1.6 and 1.4 cm respectively.
P. Haghighatmehr; M. J. Valadanzouj; R. Tajik; S. Jabari; M. R. Sahebi; R. Eslami; M. Ganjiyan; M. Dehghani
Abstract
A large area in Hashtgerd plain, in southwest of Tehran, is subject to the land subsidence induced by overexploitation of groundwater. In this paper, in order to study the subsidence SAR interferometry (InSAR) and global positioning system (GPS) are used. The small baseline subset (SBAS) algorithm is ...
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A large area in Hashtgerd plain, in southwest of Tehran, is subject to the land subsidence induced by overexploitation of groundwater. In this paper, in order to study the subsidence SAR interferometry (InSAR) and global positioning system (GPS) are used. The small baseline subset (SBAS) algorithm is used for deformation time series analysis. Time series analysis is performed using 6 interferograms calculated from 4 ENVISAT ASAR data spanning 4 months in 2008. A smoothing constraint that reduces the atmospheric noise, unwrapping and orbital errors whereas it preserves the non-linear deformation features is added to the least-squares solution. The time series results revealed that the area is subsiding continuously. Mean LOS deformation velocity map obtained from time series analysis demonstrated a considerable subsidence rate of 47 (mm/month). In order to assess the time series analysis results a dense GPS network consisting of 18 measuring stations is then established. The network design is carried out based on the subsidence spatial pattern extracted from an interferogram calculated from radar data of 2003-2004. The GPS stations are collecting the data simultaneously with radar data acquisitions. Horizontal and vertical components of the subsidence are extracted from GPS measurements. The comparison of InSAR and GPS time series shows the high compatibility of the results demonstrating the high performance of InSAR technique.
M. Amighpey; S. Arabi; A. Talebi
Abstract
Blemish of subsidence and land ruptures such as destroying aquifer systems, damaging structures and disordering water main, are usually irreparable and expensive. One of the regions with a high rate subsidence in Iran is the Yazd-Ardakan plain that subsides with a maximum rate of 12 cm per year based ...
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Blemish of subsidence and land ruptures such as destroying aquifer systems, damaging structures and disordering water main, are usually irreparable and expensive. One of the regions with a high rate subsidence in Iran is the Yazd-Ardakan plain that subsides with a maximum rate of 12 cm per year based on levelling and InSAR observation. It is obvious that such a high rate subsidence is the result of water extra exploiting and groundwater levels at piezometric wells confirm this in the region. Management of water drafting in this region is a necessary work in this region.
H. Fattahi; M. J. Valadan Zouj; M. R. Mobasheri; M. Dehghani
Abstract
Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, ...
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Interferometric Synthetic Aperture Radar (InSAR) technique using phase information has demonstrated its abilities in topographic mapping and measuring surface deformation with the precision of meter and sub-centimeter, respectively in a very high spatial resolution. However, various limiting factors such as spatial and temporal decorrelation, atmospheric effects and thermal noise of the radar sensor introduce different types of noise into the interferograms, which makes the phase unwrapping too difficult to obtain the accurate results. In this study, an algorithm for noise suppression is presented based on wavelet transform in the complex domain. The high-frequency data due to the phase jumps is not appeared in the complex domain. Therefore, the wavelet coefficients obtained in the complex domain include mostly the noise. The wavelet coefficients of the noisy interferogram are then filtered using the threshold computed from the related wavelet band. In comparison with the other noise reduction methods such as multi-look processing and those based on Fourier transform in small windows, the proposed algorithm can reduce the noise while keeping the spatial resolution without the need for windowing the interferogram. Quantitative and qualitative evaluations of the results obtained by the new method applied on the simulated and real noisy data show high performance of the wavelet transform in noise reduction.
