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- Nilfouroushan, Faramarz, Senior Lecturer, 1968-, et al.
(författare)
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Reprocessing and analysis of 20-years SWEREF stations GPS data using BERNESE and GAMIT software
- 2018
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Konferensbidrag (refereegranskat)abstract
- SWEREF 99 has been used as the national geodetic reference frame in Sweden since 2007 and is adopted by EUREF as an ETRS89 realization. It is defined by an active approach through the 21 original SWEPOS stations, hence relying on positioning services like the network RTK service and the post processing service. All alterations of equipment and software as well as movements at the reference stations will in the end affect the coordinates. For checking the effect of all alterations mentioned above and having a backup network of GNSS stations, approximately 300 nationally distributed passive so-called consolidation points are used. The main part of the consolidation points consists of so-called SWEREF points established already with the beginning in the mid-1990s. All stations are remeasured with static GNSS for 2x24 hours using choke ring antennas in a 6 years base with 50 points each year. The original processing was done with the Bernese GNSS software and the reprocessing was carried out with both the Bernese GNSS software and the GAMIT software in 2017-18 covering so far 20 years of data. The station coordinates were first estimated in ITRF2008 and then transformed to SWEREF 99 using the new land uplift model NKG2016LU and close by reference stations. The outcome will be used to analyse the stability of SWEREF 99 after two decades and has been used to define the SWEREF 99 component in the fit of the SWEN17_RH2000 geoid model to SWEREF 99 and RH 2000. Our analysis show a very good agreement between repeated measurements. The mean RMS of the SWEREF 99 coordinates which have had 3-times measurements (every ~6 years) is 2 mm for the horizontal components and 5-6 mm for height. Moreover, we did trend analysis to investigate the stability of the stations and check if any systematic trend exists in the transformed SWEREF99 coordinates. In general, no significant trend was observed. However, at some stations trends were observed due to local ground movements.
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| 2. |
- Pease, Victoria, et al.
(författare)
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Development of the Amerasia Basin: Where are we now?
- 2018
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Konferensbidrag (refereegranskat)abstract
- This contribution reviews our current understanding of the tectonic development of the Amerasia Basin and presents new analogue modelling results relating to its formation. The Amerasia Basin is separated into the Canada Basin and the Makarov-Povodnikov basins by the Alpha-Mendeleev Ridges. Published data supports a conjugate relationship between the Alaskan and Canadian Arctic margins, in which counterclockwise rotation of Arctic Alaska from Arctic Canada resulted in the opening of the Canada Basin. Thus the tectonic development of the Canada Basin is ‘broadly’ understood, although its precise timing and the role of the Chukchi Plateau remain disputed. This leaves the Amerasia Basin and we identify two significant barriers to understanding its tectonic development: i) The northward extent of the Canada Basin fossil spreading ridge, and ii) the role of LIP magmatism. In assessing the former, we constructed a series of two-plate analogue models with properties homologous of homogeneous continental crust and simulated extension between the plates around a common rotation axis. In all models, a triangular (ocean) basin forms between the two ‘diverging’ plates, however, depending on the mode of opening and initial plate configuration transpressive, transtensive, and ‘pure’ strike-slip structures can be generated. Plates with a fixed pole of rotation that move at the same rate produce a basin that widens away from the pole along a straight ridge, whereas models with a migrating pole of rotation produce a bend in the spreading ridge and this may explain the curved ridge observed in the Canada Basin. Both models produce strike-slip faults of reversed polarity in the region opposite the pole. If the spreading ridge extended to the Lomonosov Ridge (LR), a strike-slip fault boundary is generated ± associated transtensive/transpressive features. Two plates with different spreading rates generate asymmetric basins, which is also a component of the Amerasia Basin. These results elucidate the consequences of sea-floor spreading in the Amerasia Basin and constrain opening scenarios.
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| 3. |
- Yazdanfar, Camellia, et al.
(författare)
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Stress transfer, aftershocks distribution and InSAR analysis of the 2005 Dahuieh earthquake, SE Iran
- 2018
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Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 0899-5362 .- 1464-343X. ; 147:86, s. 211-219
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the authors studied the 2005 Dahuieh Zarand earthquake in SE Iran by combining Coulomb stress changes, InSAR study, locally recorded aftershocks and their spatial correlations, co-seismic slip distributions, Iso-seismal curves, and strong ground motion data. The event (MW 6.4) occurred in Kerman province, SE Iran, on February 22, 2005. The locally recorded aftershocks were used to calculate the Coulomb stress changes and the decay time based on Omori’s law. The decay time of aftershocks calculated by Omori’s law was about 500 days. A great correlation was particularly deduced from the spatial distribution of the aftershocks and areas of increased Coulomb stress for optimal strike slip faults. Moreover, using SAR Interferograms, we determined the postseismic surface deformations. Also, the majority of the coseismic slips occurred in the eastern part, where there was sparsely distributed aftershocks. The deformation maps showed active uplift for at least 300 days after the main shock. We reconciled time decays of the aftershocks with the postseismic uplifts, calculated from InSAR. In our model, which is based on after slip evolution, for one of the postseismic relaxation mechanisms, we found a proper correlation between the aftershock decay time and InSAR displacement maps to define postseismic motions. There is also a reasonable correspondence between the mainshock intensity, the acceleration map, and postseismic ground uplift, estimated by InSAR.
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