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- Abrehdary, Majid, et al.
(författare)
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Modelling Moho depth in ocean areas based on satellite altimetry using Vening Meinesz–Moritz’ method
- 2016
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Ingår i: Acta Geodaetica et Geophysica Hungarica. - : Springer Netherlands. - 1217-8977 .- 1587-1037 .- 2213-5812 .- 2213-5820. ; 51:2, s. 137-149
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Tidskriftsartikel (refereegranskat)abstract
- An experiment for estimating Moho depth is carried out based on satellite altimetryand topographic information using the Vening Meinesz–Moritz gravimetric isostatichypothesis. In order to investigate the possibility and quality of satellite altimetry in Mohodetermination, the DNSC08GRA global marine gravity field model and the DTM2006 globaltopography model are used to obtain a global Moho depth model over the oceans with aresolution of 1 x 1 degree. The numerical results show that the estimated Bouguer gravity disturbancevaries from 86 to 767 mGal, with a global average of 747 mGal, and the estimatedMoho depth varies from 3 to 39 km with a global average of 19 km. Comparing the Bouguergravity disturbance estimated from satellite altimetry and that derived by the gravimetricsatellite-only model GOGRA04S shows that the two models agree to 13 mGal in root meansquare (RMS). Similarly, the estimated Moho depths from satellite altimetry andGOGRA04S agree to 0.69 km in RMS. It is also concluded that possible mean dynamictopography in the marine gravity model does not significantly affect the Moho determination.
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| 2. |
- Alizadeh Khameneh, Mohammad Amin, et al.
(författare)
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The Effect of Instrumental Precision on Optimisation of Displacement Monitoring Networks
- 2016
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Ingår i: Acta Geodaetica et Geophysica Hungarica. - : Springer Science and Business Media LLC. - 1217-8977 .- 1587-1037 .- 2213-5812 .- 2213-5820. ; 51:4, s. 761-772
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Tidskriftsartikel (refereegranskat)abstract
- In order to detect the geo-hazards, different deformation monitoring networks are usually established. It is of importance to design an optimal monitoring network to fulfil the requested precision and reliability of the network. Generally, the same observation plan is considered during different time intervals (epochs of observation). Here, we investigate the case that instrumental improvements in sense of precision are used in two successive epochs. As a case study, we perform the optimisation procedure on a GPS monitoring network around the Lilla Edet village in the southwest of Sweden. The network was designed for studying possible displacements caused by landslides. The numerical results show that the optimisation procedure yields an observation plan with significantly fewer baselines in the latter epoch, which leads to saving time and cost in the project. The precision improvement in the second epoch is tested in several steps for the Lilla Edet network. For instance, assuming two times better observation precision in the second epoch decreases the number of baselines from 215 in the first epoch to 143 in the second one.
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| 3. |
- Bagherbandi, Mohammad, et al.
(författare)
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A new Fennoscandian crustal thickness model based on CRUST1.0 and a gravimetric-isostatic approach
- 2015
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Ingår i: Earth-Science Reviews. - : Elsevier BV. - 0012-8252 .- 1872-6828. ; 145, s. 132-145
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Forskningsöversikt (refereegranskat)abstract
- In this paper a new gravimetric-isostatic crustal thickness model (VMM14_FEN) is estimated for Fennoscandia. The main motivation is to investigate the relations between geological and geophysical properties, the Moho depth and crust-mantle density contrast at the crust-mantle discontinuity. For this purpose the Bouguer gravity disturbance data is corrected in two main ways namely for the gravitational contributions of mass density variation due to the different layers of the Earth's crust such as ice and sediments, as well as for the gravitational contribution from deeper masses below the crust. This second correction (for non-isostatic effects) is necessary because in general the crust is not in complete isostatic equilibrium and the observed gravity data are not only generated by the topographic/isostatic masses but also from those in the deep Earth interior. The correction for non-isostatic effects is mainly attributed to unmodeled mantle and core boundary density heterogeneities. These corrections are determined using the recent seismic crustal thickness model CRUST1.0. We compare our modeling results with previous studies in the area and test the fitness. The comparison with the external Moho model EuCRUST-07 shows a 3.3. km RMS agreement for the Moho depth in Fennoscandia. We also illustrate how the above corrections improve the Moho depth estimation. Finally, the signatures of geological structures and isostatic equilibrium are studied using VMM14_FEN, showing how main geological unit structures attribute in isostatic balance by affecting the Moho geometry. The main geological features are also discussed in the context of the complete and incomplete isostatic equilibrium.
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| 7. |
- Sjöberg, Lars E.
(författare)
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Closed-form and iterative weighted least squares solutions of Helmert transformation parameters
- 2013
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Ingår i: Journal of Geodetic Science. - : Walter de Gruyter GmbH. - 2081-9919 .- 2081-9943. ; 3:1, s. 7-11
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Tidskriftsartikel (refereegranskat)abstract
- The Helmert transformation is the most common transformation between different geodetic systems. In 2-D, in contrast to higher dimensions, it is a well-known procedure how to determine the 4 transformation parameters in a closed form. Here we derive the closed-form weighted least squares solution in m-dimensional space for an arbitrary number (≥ m) of coordinate set-ups in two related systems. The solution employs singular value decomposition (SVD) for the rotation matrix, while the translation vector and scale parameters are obtained in simpler ways. To avoid the SVD routine, we also present an iterative approach to solve for the rotation matrix. The paper is completed with a test procedure for detecting outlying coordinate pairs.
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