| 1. |
- Bagherbandi, Mohammad, et al.
(författare)
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A study on the relationship between isostatic equilibrium and seismicity : A case study in Africa
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Ingår i: Journal of Geodynamics. - 0264-3707 .- 1879-1670.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The principle of isostasy plays an important role in understanding the relationship between the geodynamic processes. It is difficult to find an exact method that delivers a complete image of the Earth structure, gravimetric and seismic methods can provide images of the interior of the Earth. The Earth’s crust parameters, i.e. crustal depth and crust-mantle density contrast, can reveal information about the solid Earth system e.g. earthquakes and continental rifting processes. In this study, a combined Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the crust and seismic activities in our study area in Africa. To do this we determine the isostatic gravity disturbance and the density contrast. Our results show that isostatic equilibrium and compensation states are closely correlated to the seismicity patterns in the study area. This paper presents a method to determine the crustal thickness and crust-mantle density contrast and consequently one can detect low-density contrasts (about 200 kg/m3) and thin crust (about 30 km) near the Afar Triangle, which confirms the state of over-compensation. Furthermore, the density structure of the mantle lithosphere shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution.
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| 2. |
- Bagherbandi, Mohammad, Professor, et al.
(författare)
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How isostasy explains continental rifting in East Africa?
- 2020
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Konferensbidrag (populärvet., debatt m.m.)abstract
- The principle of isostasy plays an important role to understand the relation between different geodynamic processes. Although, it is difficult to find an exact method that delivers a complete image of the Earth structure. However, gravimetric methods are alternative to provide images of the interior of the Earth. The Earth’s crust parameters, i.e. crustal depth and crust-mantle density contrast, can reveal adequate information about the solid Earth system such as volcanic activity, earthquake and continental rifting. Hence, in this study, a combine Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the lithosphere and seismic activities in East Africa. Our results show that isostatic equilibrium and compensation states are closely correlated to the seismicity patterns in the study area. For example, several studies suggest that African superplume causes the rift valley, and consequently differences in crustal and mantle densities occur. This paper presents a method to determine the crustal thickness and crust-mantle density contrast and consequently one can observe low-density contrast (about 200 kg/m3 ) and thin crust (about 30 km) near the triple junction plate tectonics in East Africa (Afar Triangle), which confirms the state of overcompensation in the rift valley areas. Furthermore, the density structure of the lithosphere shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution across East Africa.
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| 3. |
- Bagherbandi, Mohammad, Professor, et al.
(författare)
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Studying permafrost using GRACE and in situ data in the northern high-latitudes regions
- 2019
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Konferensbidrag (populärvet., debatt m.m.)abstract
- There is an exceptional opportunity of achieving simultaneous and complementary data from a multitude of geoscience and environmental near-earth orbiting artificial satellites to study phenomena related to the climate change e.g. sea level change, ice melting, soil moisture variation, temperature changes, and earth surface deformations. In this study, we focus on permafrost thawing and its associated gravity change, and organic material changes using GRACE data and other satellite- and ground-based observations. The estimation of permafrost changes requires combining information from various sources, particularly using the gravity field change, surface temperature change, and GIA. The most significant factor for careful monitoring of the permafrost thawing is the fact that this process could be responsible for releasing an additional enormous amount of greenhouse gases emitted to the atmosphere, most importantly to mention Carbone dioxide and Methane that are currently stored in the frozen ground. The results of a preliminary numerical analysis reveal a possible existence of a high correlation between the secular trends of greenhouse gases, temperature and equivalent water thickness in the selected regions. Furthermore, according to our estimates based on processing the GRACE data, the groundwater storage attributed to the due to permafrost thawing increased at the annual rates of 3.4, 3.8, 4.4 and 4.0 cm, in Siberia, northern Alaska, and Canada. Despite a rather preliminary character of our results, these findings indicate that the methodology developed and applied in this study should be improved by incorporating the in situ permafrost measurements.
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| 4. |
- Gido, Nureldin A. A., et al.
(författare)
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A gravimetric method to determine horizontal stress field due to flow in the mantle in Fennoscandia
- 2019
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Ingår i: Geosciences Journal. - : Springer. - 1226-4806 .- 1598-7477. ; 23:3, s. 377-389
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Tidskriftsartikel (refereegranskat)abstract
- Mass changes and flow in the Earth's mantle causes the Earth's crust not only to movevertically, but also horizontally and to tilt, and produce a major stress in the lithosphere.Here we use a gravimetric approach to model sub-lithosphere horizontal stress in theEarth's mantle and its temporal changes caused by geodynamical movements likemantle convection in Fennoscandia. The flow in the mantle is inferred from tectonicsand convection currents carrying heat from the interior of the Earth to the crust. Theresult is useful in studying how changes of the stress influence the stability of crust.The outcome of this study is an alternative approach to studying the stress and itschange using forward modelling and the Earth's viscoelastic models. We show that thedetermined horizontal stress using a gravimetric method is consistent with tectonicsand seismic activities. In addition, the secular rate of change of the horizontal stress,which is within 95 kPa/year, is larger outside the uplift dome than inside.
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| 5. |
- Gido, Nureldin A. A., et al.
(författare)
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Localized Subsidence Zones in Gavle City Detected by Sentinel-1 PSI and Leveling Data
- 2020
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Ingår i: Remote Sensing. - : MDPI. - 2072-4292. ; 12:16
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Tidskriftsartikel (refereegranskat)abstract
- Among different sets of constraints and hazards that have to be considered in the management of cities and land use, land surface subsidence is one of the important issues that can lead to many problems, and its economic consequences cannot be ignored. In this study, the ground surface deformation of Gavle city in Sweden is investigated using the Persistent Scatterer Interferometry (PSI) technique as well as analyzing the historical leveling data. The PSI technique is used to map the location of hazard zones and their ongoing subsidence rate. Two ascending and descending Sentinel-1 datasets, collected between January 2015 and May 2020, covering the Gavle city, were processed and analyzed. In addition, a long record of a leveling dataset, covering the period from 1974 to 2019, was used to detect the rate of subsidence in some locations which were not reported before. Our PSI analysis reveals that the center of Gavle is relatively stable with minor deformation ranged between -2 +/- 0.5 mm/yr to +2 +/- 0.5 mm/yr in vertical and east-west components. However, the land surface toward the northeast of the city is relatively subsiding with a higher annual rate of up to -6 +/- 0.46 mm/yr. The comparison at sparse locations shows a close agreement between the subsidence rates obtained from precise leveling and PSI results. The regional quaternary deposits map was overlaid with PSI results and it shows the subsidence areas are mostly located in zones where the subsurface layer is marked by artificial fill materials. The knowledge of the spatio-temporal extents of land surface subsidence for undergoing urban areas can help to develop and establish models to mitigate hazards associated with such land settlement.
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| 6. |
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| 7. |
- Gido, Nureldin A. A.
(författare)
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Monitoring lithospheric motions by Satellite geodesy
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Understanding of global and local Earth’s dynamic processes is of great importance to the Earth’s system knowledge, human life, and sustainability goals (e.g. climatic change and geo-hazard assessment, etc.). The processes are largely affected by the Earth's mass distribution and redistribution, which can be quantified and modelled using simultaneous and complementary data from various geoscience and environmental near earth-orbiting artificial satellites. In this thesis, which is based on five peer-reviewed papers, we study the lithospheric motion and the Earth’s mass change in terms of gravity variation, using a combination of geodetic satellite data and non-geodetic observations. The first paper is concerned with using of gravimetric approach to model sub-crustal horizontal stresses in the Earth’s mantle and their temporal changes using the Gravity Recovery and Climate Experiment (GRACE) data, caused by geodynamical processes such as mantle convection, in Fennoscandia region. We show that the determined horizontal stresses obtained by a gravimetric method are consistent with tectonics and seismic activities. In addition, the secular rate of change of the horizontal stress, which is within 95 kPa/year, is larger outside the uplift dome than inside in the study area. In the second paper, permafrost thawing and its associated gravity change, in terms of groundwater storage (GWS) anomalies changes is studied using the GRACE data and other satellites (e.g. AIRS) and ground-based observations in the northern high-latitude regions. The results of a preliminary numerical analysis reveal a high correlation between the secular trends of greenhouse gases (CO2), temperature, and the equivalent water thickness in the selected regions. Furthermore, the GRACE-based GWS estimates attributed to the permafrost thawing is increased at the annual rates of 3 to 4 cm/year in selected study areas. The third paper investigates the large-scale GRACE-based GWS changes together with different hydrological models over the major oil reservoirs in Sudan. The outcomes are correlated with the available oil wells production data. Moreover, using the freely available Sentinel-1 data, the ground surface deformation associated with oil and water depletion is studied. Our results show that there is a significant correlation between the GRACE-based GWS anomalies and the extracted oil and water volumes. The trend of GWS anomaly changes due to water and oil depletion varies from -18.5 ± 6.3 to -6.2 ± 1.3 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 Synthetic Aperture Radar (SAR) data analysis using Persistent Scatterer Interferometry (PSI) method shows high rate of subsidence, i.e. -24.5 ± 0.85, -23.8 ± 0.96, -14.2 ± 0.85 and -6 ± 0.88 mm/year, over the selected study area.In the fourth paper, a combined Moho model using seismic and gravity data is determined to investigate the relationship between the isostatic state of the lithosphere and seismic activities in the study area (which includes East Africa, Egypt, Congo and Saudi Arabia). Our results show that isostatic equilibrium and compensation state are closely correlated to the seismicity patterns in the study area. This paper presents a method to determine the crustal thickness and crust-mantle density contrast, and consequently one can detect low-density contrast (about 200 kg/m3) and thin crust (about 30 km) near the triple junction plate tectonics in East Africa (Afar triple junction), which confirms the state of over-compensation in the rift valley areas. Furthermore, the density contrast structure of the crust-mantle shows a large correlation with the earthquake activity, sub-crustal stress and volcanic distribution across East Africa. The fifth and last paper investigates the ground surface deformation of Gävle city in Sweden using Sentinel-1 data and PSI technique, as well as analyzing the historical leveling data. The PSI technique is used to map the location of risk zones, and their ongoing subsidence rate. Our PSI analysis reveals that the centre of Gävle city is relatively stable with minor deformation ranging between -2.0 mm/year and +2.0 mm/year in the vertical and East-West components. Furthermore, the land surface toward the northeast of the city is significantly subsiding with an annual rate of about -6 mm/year. The comparison at sparse locations shows a close agreement between the subsidence rates obtained from precise leveling and PSI results. The regional quaternary deposit distribution was correlated with PSI results, and it shows that the subsidence areas are mostly located in zones where the sub-surface layer is marked by artificial fill materials.
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| 8. |
- Gido, Nureldin A. A., et al.
(författare)
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Satellite monitoring of mass changes and ground subsidence in Sudan’s oil fields using GRACE and Sentinel-1 data
- 2020
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Konferensbidrag (populärvet., debatt m.m.)abstract
- Monitoring environmental hazards, due to natural and anthropogenic causes, is one of the important issues, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, e.g. the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this aspect. GRACE missions are dedicated to model the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects Synthetic Aperture Radar (SAR) data which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure, form compaction and consequently land subsidence occurs which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, i.e. Heglig, Bamboo, Neem, Diffra and Unity-area oil fields. Then we correlate the results with the available oil wells production data for the period of 2003-2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Due to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS change and extracted oil and water volumes. The trend of GWS changes due to water and oil depletion ranged from -18.5 to -6.2mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using Persistent Scatterer Interferometry (PSI) method shows high rate of subsidence i.e. -24.5, -23.8, -14.2 and -6 mm/year over Heglig, Neem, Diffra and Unity-area oil fields respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.
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| 9. |
- Gido, Nureldin A. A., et al.
(författare)
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Satellite Monitoring of Mass Changes and Ground Subsidence in Sudan's Oil Fields Using GRACE and Sentinel-1 Data
- 2020
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Ingår i: Remote Sensing. - : MDPI AG. - 2072-4292. ; 12:11
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Tidskriftsartikel (refereegranskat)abstract
- Monitoring environmental hazards, owing to natural and anthropogenic causes, is an important issue, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, for example, the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this respect. GRACE missions are dedicated to modeling the temporal variations of the Earth's gravity field and mass transportation in the Earth's surface, whereas Sentinel-1 collects synthetic aperture radar (SAR) data, which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure and form compaction and, consequently, land subsidence occurs, which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, that is, Heglig, Bamboo, Neem, Diffra, and Unity-area oil fields. Then, we correlate the results with the available oil wells production data for the period of 2003-2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Owing to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS anomalies (Delta GWS) and extracted oil and water volumes. The trend of Delta GWS changes due to water and oil depletion ranged from -18.5 +/- 6.3 to -6.2 +/- 1.3 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using the persistent scatterer interferometry (PSI) method shows a high rate of subsidence, that is, -24.5 +/- 0.85, -23.8 +/- 0.96, -14.2 +/- 0.85, and -6 +/- 0.88 mm/year over Heglig, Neem, Diffra, and Unity-area oil fields, respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.
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| 10. |
- Gido, Nureldin A. A., et al.
(författare)
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Studying permafrost by integrating satellite and in situ data in the northern high-latitude regions
- 2019
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Ingår i: Acta Geophysica. - : Springer. - 1895-6572 .- 1895-7455. ; 67:2, s. 721-734
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Tidskriftsartikel (refereegranskat)abstract
- There is an exceptional opportunity of achieving simultaneous and complementary data from a multitude of geoscience and environmental near-earth orbiting artificial satellites to study phenomena related to the climate change. These satellite missions provide the information about the various phenomena, such as sea level change, ice melting, soil moisture variation, temperature changes and earth surface deformations. In this study, we focus on permafrost thawing and its associated gravity change (in terms of the groundwater storage), and organic material changes using the gravity recovery and climate experiment (GRACE) data and other satellite- and ground-based observations. The estimation of permafrost changes requires combining information from various sources, particularly using the gravity field change, surface temperature change, and glacial isostatic adjustment. The most significant factor for a careful monitoring of the permafrost thawing is the fact that this process could be responsible for releasing an additional enormous amount of greenhouse gases emitted to the atmosphere, most importantly to mention carbon dioxide (CO2) and methane that are currently stored in the frozen ground. The results of a preliminary numerical analysis reveal a possible existence of a high correlation between the secular trends of greenhouse gases (CO2), temperature and equivalent water thickness (in permafrost active layer) in the selected regions. Furthermore, according to our estimates based on processing the GRACE data, the groundwater storage attributed due to permafrost thawing increased at the annual rates of 3.4, 3.8, 4.4 and 4.0 cm, respectively, in Siberia, North Alaska and Canada (Yukon and Hudson Bay). Despite a rather preliminary character of our results, these findings indicate that the methodology developed and applied in this study should be further improved by incorporating the in situ permafrost measurements.
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