Shirzaei M.,German Research Center for Geosciences |
Walter T.R.,German Research Center for Geosciences |
Nankali H.R.,National Cartographic Center |
Holohan E.P.,German Research Center for Geosciences |
Holohan E.P.,University College Dublin
Geology | Year: 2011
The detection and monitoring of gravity-driven volcano deformation are vital for understanding volcanic hazards such as landslides, lateral blasts, and debris avalanches. Although deformation has been detected at several large active volcanoes (e.g., Mount Etna, Vesuvius, Kilauea), these systems also exhibit persistent magmatic activity, obscuring the gravity-driven signals of ground motion. In this study we present a first interferometric synthetic aperture radar (InSAR) deformation time series at the dormant Damavand volcano in northern Iran, over the period A.D. 2003-2008. The high-resolution data show a lateral extension of the volcano at the relative rate of as much as ~6 mm/yr accompanied by subsidence at the rate of as much as ~5 mm/yr at the volcano summit. We find that lateral motion of the east flank is more significant than that of the west flank. On the basis of past understanding and modeling of deforming volcanoes elsewhere, we interpret this new evidence to reveal long-term, slow, gravitydriven deformation, possibly in the form of gravitational spreading, at Damavand. This persistent deformation activity is well expressed, although no volcanic activity was ever reported in history. This finding shows that magmatic activity is not required for spreading and highlights the importance of identifying long-lived gravity-driven deformation for hazard assessment at dormant or inactive volcanoes. © 2011 Geological Society of America.
Djamour Y.,P.A. College |
Vernant P.,Montpellier University |
Nankali H.R.,National Cartographic Center |
Tavakoli F.,National Cartographic Center
Earth and Planetary Science Letters | Year: 2011
A network of continuous GPS stations has been installed in NW Iran since 2005 to complement the survey GPS network already existing in the region. We present the 1999-2009 GPS-derived velocity field for this region based on the continuous and survey-mode observations. The results confirm a right lateral slip of 7 ± 1. mm/yr for the North Tabriz fault, in agreement with previous studies. This rate is consistent with earthquakes of magnitude 7-7.3 and recurrence times of 250-300. yr. The higher spatial coverage of the new network shows that deformation is localized in the vicinity of the Chalderan, south Gailatu-Siah Cheshmeh-Khoy fault and the North Tabriz fault. However the eastern end of the North Tabriz fault appears to cross Mount Bozgush rather than following its southern foothills. This new velocity field does not indicate the 8. mm/yr of NNE-SSW extension suggested earlier for the region, but rather shows lower extension of 1-2 ± 1. mm/yr across the eastern segment of the North Tabriz fault and the Talesh. To the west, the Chalderan and the western North Tabriz fault segment act like pure strike slip faults without significant extension or compression. The denser network in the Rudbar earthquake region (Ms 7.3, 1992) shows no significant motion across the fault, suggesting that the recurrence time of earthquakes like the Rudbar event must be very long. The lack of substantial compressive strain and the sharp azimuth change of the velocity vectors in the transition zone from Arabia to Lesser Caucasus motion imply that processes other than "extrusion", possibly related to old subduction or delamination, contribute to active deformation. © 2011 Elsevier B.V.
Karimzadeh S.,Kanazawa University |
Cakir Z.,Technical University of Istanbul |
Osmanoglu B.,University of Alaska Fairbanks |
Schmalzle G.,University of Washington |
And 3 more authors.
Journal of Geodynamics | Year: 2013
We present the surface deformation along the North Tabriz Fault (NTF) deduced from Synthetic Aperture Radar Interferometry (InSAR) technique. The NTF, a major right-lateral strike-slip fault within the active Arabia-Eurasia collision zone, is located 40-45. km southwest of the Mw 6.5 and Mw 6.3, August 11, 2012 earthquake sequence that caused heavy damage and more than 300 deaths in Ahar, NW Iran. InSAR time series analysis of 17 ENVISAT radar images acquired between 2004 and 2010 using combination of the permanent scatterers InSAR (PSI) and the small baseline InSAR (SBAS) approach reveals sub-centimeter interseismic strain accumulation across the NTF and rapid subsidence in the Tabriz basin. Elastic dislocation modeling of the mean line-of-sight velocity field estimated from SBAS time series yields an average slip rate of 8.7 ± 2.5. mm/year with a locking depth of 15.8 ± 10.8. km. This rate is consistent with previous geodetic estimates based on recent Global Positioning System measurements, and suggests a recurrence interval of 250-300 years for major earthquakes of Mw 7.0-7.3 on the NTF, much shorter than those estimated from paleoseismic investigations (821 ± 176 years). This in turn implies a high seismic potential on the NTF taking into account the occurrence of the two last earthquakes on the NTF in 1721 and 1780. SAR time series analysis also reveals three regions of rapid subsidence with a maximum rate of 20. mm/year near the Tabriz thermal power plant in the Tabriz basin. Piezometric data from groundwater wells suggest that accelerated subsidence over the last several years may result from fluctuations in the ground water table. © 2013 Elsevier Ltd.
Mousavi Z.,Joseph Fourier University |
Mousavi Z.,National Cartographic Center |
Walpersdorf A.,Joseph Fourier University |
Walker R.T.,University of Oxford |
And 5 more authors.
Earth and Planetary Science Letters | Year: 2013
We present a velocity field compiled from a network of 27 permanent and 20 campaign GPS stations across NE Iran. This new GPS velocity field helps to investigate how Arabia-Eurasia collision deformation is accommodated at the northern boundary of the deforming zone. The present-day northward motion decreases eastward from 11 mm/yr at Tehran (~52°E) to 1.5 mm/yr at Mashhad (~60°E). N-S shortening across the Kopeh Dagh, Binalud and Koh-e-Sorkh ranges sums to 4.5 ± 0.5 mm/yr at longitude 59°E. The available GPS velocities allow us to describe the rigid-body rotation of the South Caspian about an Euler pole that is located further away than previously thought. We suggest that two new stations (MAVT and MAR2), which are sited far from the block boundaries, are most likely to indicate the full motion of the South Caspian basin. These stations suggest that NW motion is accommodated by right-lateral slip on the Ashkabad fault (at a rate of up to 7 mm/yr) and by up to 4-6 mm/yr of summed left-lateral slip across the Shahroud left-lateral strike-slip system. Our new GPS results are important for assessing seismic hazard in NE Iran, which contains numerous large population centers and possesses an abundant historical earthquake record. Our results suggest that the fault zones along the eastern Alborz and western Kopeh Dagh may accommodate slip at much faster rates than previously thought. Fully assessing the role of these faults, and the hazard that they represent, requires independent verification of their slip-rates through additional GPS measurements and geological fieldwork. © 2013 Elsevier B.V.
Djamour Y.,Montpellier University |
Vernant P.,Montpellier University |
Bayer R.,Montpellier University |
Nankali H.R.,National Cartographic Center |
And 8 more authors.
Geophysical Journal International | Year: 2010
A network of 54 survey GPS sites, 28 continuous GPS stations and three absolute gravity (AG) observation sites have been set up in the Alborz mountain range to quantify the present-day kinematics of the range. Our results allow us to accurately estimate the motion of the South Caspian block (SCB) for the first time, and indicate rotation of the SCB relative to Eurasia, accounting for the left lateral motion in the Alborz range. In light of these new results, it clearly appears that deformation rates vary along the range, the eastern part accommodating mainly left lateral strike slip (2 mm yr-1 south of the range and 5 mm yr-1 north of the range) with a very low range normal shortening rate on the Khazar thrust fault (~2 mm yr-1), and the western part accommodating range normal shortening (~6 mm yr-1) on the Khazar thrust fault with a left lateral component of ~2 mm yr-1 north of the range and 1 mm yr-1 south of the range. These present-day kinematics agree with geomorphologic estimated slip rates, but not the long-term deformation, corroborating the idea that the kinematics of the range have changed recently due to the change of SCB motion.Modelling of the interseismic deformation suggests a deep locking depth on the central-western segment of the Khazar fault (~30 km) in agreement with the Baladeh earthquake rupture and aftershock ranging between 10 and 30 km. Given this unusual deep locking depth and the 34° dip of the thrust, a large part of the Alborz range is located above the seismically coupled part of the fault. Based on our AG measurements this part of the range seems to uplift at a rate of 1-5 mm yr-1, in agreement with terrace uplift. © 2010 The Authors Geophysical Journal International © 2010 RAS.
Rolland L.M.,University of Nice Sophia Antipolis |
Vergnolle M.,University of Nice Sophia Antipolis |
Nocquet J.-M.,University of Nice Sophia Antipolis |
Sladen A.,University of Nice Sophia Antipolis |
And 4 more authors.
Geophysical Research Letters | Year: 2013
It has previously been suggested that ionospheric perturbations triggered by large dip-slip earthquakes might offer additional source parameter information compared to the information gathered from land observations. Based on 3D modeling of GPS- and GLONASS-derived total electron content signals recorded during the 2011 Van earthquake (thrust, intra-plate event, M w = 7.1, Turkey), we confirm that coseismic ionospheric signals do contain important information about the earthquake source, namely its slip mode. Moreover, we show that part of the ionospheric signal (initial polarity and amplitude distribution) is not related to the earthquake source, but is instead controlled by the geomagnetic field and the geometry of the Global Navigation Satellite System satellites constellation. Ignoring these non-tectonic effects would lead to an incorrect description of the earthquake source. Thus, our work emphasizes the added caution that should be used when analyzing ionospheric signals for earthquake source studies. © 2013 American Geophysical Union. All Rights Reserved.
Bagheri H.,Tafresh University |
Sadeghian S.,National Cartographic Center
2014 Iranian Conference on Intelligent Systems, ICIS 2014 | Year: 2014
In the recent decades, the determination and evaluation of geometrical correction models as well as georeferencing satellite images have been of great consideration due to their frequent use in various fields, and are regarded a leading topic in photogrammetry and remote sensing. This paper is about the geometric correction of the Worldview-2 satellite image using different modeling methods and tries to give an overall evaluation of strength of various possible modeling for a prototype image of an urban area like Tehran. The distribution and number of control points with regard to their effects in each modeling method were examined which resulted in a high precision of a final geometry correction about 0.36 meter using rational functions. For more optimization artificial intelligent methods like genetic algorithms and neural networks were used. With the use of perceptron network, a result of 0.84 pixels with 4 neurons in middle layer was gained and the final conclusion was that with these algorithms it is possible to optimize the existing models and have better results than usual ones. © 2014 IEEE.
Ardalan A.A.,University of Tehran |
Ardalan A.A.,National Cartographic Center |
Rezvani M.-H.,University of Tehran
IEEE Transactions on Aerospace and Electronic Systems | Year: 2015
Multiple Global Navigation Satellite System (GNSS) antennae systems have been among the well-known approaches to attitude determination of moving platforms in recent years. However, the constraints on the onboard GNSS antennae configuration, that is, installing the antennae baselines along the main axes of the platform, can lead to practical difficulties and inevitable uncertainty. In this contribution we present an iterative method to obtain the accurate attitudes by means of the onboard misaligned baselines. In order to remove the effects of the horizontal and vertical misalignments from GNSS observations of the baselines, attitude-induced corrections have been developed through the relative lever-arm coordinates of the onboard antennae. This approach provides us with more freedom from spatial distribution of the onboard antennae. The performance of the proposed method has been analyzed by simulated data and an actual experiment in low- and high-dynamic situations. The simulation has been designed to evaluate the capability and reliability of the iterative method under the presence of small and large misalignments. The field experiment was carried out in the offshore waters of Kish harbor using three dual-frequency GNSS receivers with choke-ring antennae onboard a survey vessel, which was also equipped with an inertial measurement unit (IMU). The maximum allowable misalignments, the convergence of the iteration, and the advantage of the proposed method over the trigonometric approach in spite of applying the traditional calibration are presented. The long-term stability of GNSS attitude determination as well as IMU accuracy degradation, due largely to the increase in the time-varying biases/noises, have demonstrated the potential of the method to estimate the accuracies and biases of the onboard inertial sensor. The overall results affirm that the presented method can effectively provide the platform attitudes using the misaligned GNSS baselines with as much flexibility as possible for the onboard antennae configuration. © 1965-2011 IEEE.
Matkan A.A.,Shahid Beheshti University |
Hajeb M.,Shahid Beheshti University |
Sadeghian S.,National Cartographic Center
Photogrammetric Engineering and Remote Sensing | Year: 2014
This paper presents a method for road extraction from lidar data based on SVM classification. The lidar data are used exclusively to evaluate the potential in the road extraction process. First, the SVM algorithm is used to classify the lidar data into five classes: road, tree, building, grassland, and cement. Then, some misclassified pixels in the road class is removed using the road values in the normalized Digital Surface Model and Normalized Difference Distance features. In the postprocessing stage, a method based on Radon transform and Spline interpolation is employed to automatically locate and fill the gaps in the road network. The experimental results show that the proposed algorithm for gap filling works well on straight roads. The proposed road extraction algorithm is tested on three datasets. An accuracy assessment indicated 63.7 percent, 60.26 percent and 66.71 percent quality for three datasets. Finally, centerline of the detected roads is extracted using mathematical morphology. © 2014 American Society for Photogrammetry and Remote Sensing.
Malihi S.,National Cartographic Center |
Maboudi M.,Islamic Azad University at Qazvin |
Pourmomena M.,National Cartographic Center
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives | Year: 2012
Digital aerial cameras are near to become the predominant sensor for photogrammetric image acquisition. The technology of GPS and IMU integrated with a digital aerial camera is a complex procedure of aerial photography with possibility of decreasing number of necessary ground control points (GCPs) for aerial triangulation (AT). Moreover, direct georeferencing, which uses calculated parameters by GPS/IMU directly, is undertaken for a range of projects. In this regard determination of the geometric relationship between GPS, IMU and camera geometry is a significant factor. Also compensation of camera rotations during the flight, which is carried out by stabilizer, plays a principle role for its successful operation. This paper will discuss calculation of 3 requisite rotational connecting parameters of geometry of camera and GPS/IMU and revise the effect of height on them.