| 1. |
- Fryksten, Jonas, et al.
(författare)
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Analysis of Clay-Induced Land Subsidence in Uppsala City Using Sentinel-1 SAR Data and Precise Leveling
- 2019
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Ingår i: Remote Sensing. - : MDPI. - 2072-4292. ; 11:23
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Tidskriftsartikel (refereegranskat)abstract
- Land subsidence and its subsequent hazardous effects on buildings and urban infrastructure are important issues in many cities around the world. The city of Uppsala in Sweden is undergoing significant subsidence in areas that are located on clay. Underlying clay units in parts of Uppsala act as mechanically weak layers, which for instance, cause sinking of the ground surface and tilting buildings. Interferometric Synthetic Aperture Radar (InSAR) has given rise to new methods of measuring movements on earth surface with a precision of a few mm. In this study, a Persistent Scatterer InSAR (PSI) analysis was performed to map the ongoing ground deformation in Uppsala. The subsidence rate measured with PSI was validated with precise leveling data at different locations. Two ascending and descending data sets were analyzed using SARPROZ software, with Sentinel-1 data from the period March 2015 to April 2019. After the PSI analyses, comparative permanent scatterer (PS) points and metal pegs (measured with precise leveling) were identified creating validation pairs. According to the PSI analyses, Uppsala was undergoing significant subsidence in some areas, with an annual rate of about 6 mm/year in the line-of-sight direction. Interestingly, the areas of great deformation were exclusively found on postglacial clay.
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| 2. |
- Kaviani, A., et al.
(författare)
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Complex pattern of seismic anisotropy beneath the Iranian plateau and Zagros
- 2019
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Konferensbidrag (refereegranskat)abstract
- We performed shear wave splitting analyses on core-refracted teleseismic shear waveforms from 150 broad-bandstations across the Iranian plateau and Zagros to investigate seismic anisotropy in the region. Seismic anisotropyis quantified by shear-wave splitting parameters, i.e. fast polarization direction and split delay time.Our measurements revealed a complex pattern of splitting parameters with variations in the trend and strength ofanisotropy across the tectonic boundaries. This complex pattern implies that a system of simple asthenosphericflow related to the absolute plate motion cannot alone explain our observations and that the lithosphere also hasa significant contribution in many parts. We compare our results to the surface deformation and velocity fieldsinferred from geodetic measurements to assess the role of the mantle in continental deformation. The rotationalpattern of the fast directions around the collision zone in Central Zagros may indicate the presence of a mantleflow around a continental keel beneath the Zagros. The agreement between the crustal and mantle deformationfield in Central Iran implies a vertically coherent deformation in this region, whereas the azimuthal variations insplitting parameters in the collision zone may suggest multi-layered anisotropy with different contributions fromthe crust and mantle.
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| 3. |
- Khorrami, F., et al.
(författare)
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An up-to-date block model and strain rate map of Iran using integrated campaign-mode and permanent GPS velocities
- 2019
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Ingår i: 27th IUGG General Assembly.
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Konferensbidrag (refereegranskat)abstract
- Iran accommodates a large part of the ongoing Arabia-Eurasia collision deformation. Because of such active tectonics, the country suffers from intensive seismicity and frequent destructive earthquakes in different locations.To study further the crustal deformation in Iran, we processed the data collected during 10 years (2006-2015) from the Iranian Permanent GNSS Network and combined them with previously published velocity solutions from GPS survey measurements during 1997–2013. We analysed this velocity field using a continuum approach to compute a new strain rate map for this region and we designed a block model based on the main geological, morphological, and seismic structures. Comparison between both approaches suggests similar results and allow us to present the first comprehensive first order fault slip rate estimates for the whole of Iran. Our results confirm most of the results from previous geodetic studies. Moreover, we also show a trade-off between the coupling ratio of the Iranian Makran subduction interface and the kinematic of the faults north of the Makran in the Jazmurian depression. Although too scarce to accurately estimate a coupling ratio, we show that coupling higher than 0.4 on the plate interface down to a depth of 25 km will induce extension on the E-W faults in the Jazmurian region. However, the sites close to the shoreline suggest a low coupling ratio, hence the coupling on this plate interface is probably more complicated than previously described and the Iranian Makran subduction interface mechanical behaviour might be similar to that on the Hellenic subduction zone.
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| 4. |
- Khorrami, Fatemeh, et al.
(författare)
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An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities
- 2019
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Ingår i: Geophysical Journal International. - : Oxford University Press. - 0956-540X .- 1365-246X. ; 217:2, s. 832-843
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Tidskriftsartikel (refereegranskat)abstract
- We present the most extensive and up-to-date unified GPS velocity field for Iran. We processed the data collected during 10 years (2006–2015) from the Iranian Permanent GNSS Network (IPGN) and combined them with previously published velocity solutions from GPS survey measurements during 1997–2013. We analysed this velocity field using a continuum approach to compute a new strain rate map for this region and we designed a block model based on the main geological, morphological, and seismic structures. Comparison between both approaches suggests similar results and allow us to present the first comprehensive first order fault slip rate estimates for the whole of Iran. Our results confirm most of the results from previous geodetic studies. But we also show a trade-off between the coupling ratio of the Iranian Makran subduction interface and the kinematic of the faults north of the Makran in the Jazmurian depression. Indeed, although too scarce to accurately estimate a coupling ratio, we show that coupling higher than 0.4 on the plate interface down to a depth of 25 km will induce extension on the E-W faults in the Jazmurian region. However, the sites close to the shoreline suggest a low coupling ratio, hence the coupling on this plate interface is probably more complicated than previously described and the Iranian Makran subduction interface mechanical behaviour might be similar to that on the Hellenic subduction zone.
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| 5. |
- Nilfouroushan, Faramarz, Senior Lecturer, 1968-, et al.
(författare)
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Maintenance of the National Realisation of ETRS89 in Sweden: re-analysis of 20-years GPS data for SWEREF stations
- 2019
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Ingår i: EUREF 2019 Symposium.
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Konferensbidrag (refereegranskat)abstract
- The national geodetic reference frame of Sweden called SWEREF 99, was adopted in 2000 by EUREF as therealization of ETRS89 in Sweden and was officially introduced in 2001 as a national reference frame, thateventually in 2007 replaced the former reference frame. The SWEREF 99 reference frame is defined by an activeapproach through the 21 fundamental SWEPOS permanent GNSS stations, hence relying on positioning servicessuch as the network real time kinematic (NRTK) and post processing service. The SWEREF 99 coordinates areassumed to be fixed in time and no temporal variations are expected. However, the stability of the stations andtheir coordinates can be altered due to equipment change or software as well as local movements at the referencestations.To be able to check all alterations mentioned above and having a backup national network of GNSS stations,approximately 300 passive so-called consolidation stations are used. The consolidation stations are a subset (mainpart) of the so-called SWEREF stations established from 1996 and onwards. All 300 stations are remeasured withstatic GNSS for 2x24 hours using choke ring antennas on a yearly basis with 50 stations each year. The originalprocessing was done with the Bernese GNSS software (here called Bernese original) and the reprocessing wascarried out with both the Bernese and the GAMIT-GLOBK software packages during 2017-2018.The resulting coordinates in SWEREF 99 from GAMIT and Bernese processing are equal at 1.2 mm level forhorizontal and 4 mm for vertical components (1 sigma) when using the same models and processing strategy.The original processing, which partly is based on other models and parameters, differs slightly more (rms 2.4mm) for the north component. Our analysis both from Bernese and GAMIT shows that the standard uncertaintiesfor a single SWEREF 99 determination (2x24 hrs) is 2 mm for the horizontal components and 6-7 mm inheight. However, since some stations are slowly moving they have slightly increased the estimated uncertainties.It is interesting to note that the repeatability is on the same level also for the original processing, where wehave differences in models and parameters used during the years. This indicates that the SWEREF-concept ofdetermining SWEREF99 coordinates has worked well on the mentioned uncertainty level.We performed trend analysis and statistical tests to investigate the stability of the estimated SWEREF 99coordinates. The analysed station time series (minimum three observations) showed that about 14% of the stationshad significant trends at the 95%-level. The possible explanation for those trends can be either local deformationand/or residuals of uplift model and/or computational effects such as lack of good or enough close-by stations forHelmert transformations from ITRF to SWEREF 99.The outcomes of the new processing and analysis reported here, are used to analyse the stability of SWEREF99 after two decades. The results have also been used to define the SWEREF 99 component in the fit of theSWEN17_RH2000 new geoid model to SWEREF 99 and RH 2000 (Swedish realization of EVRS).
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| 6. |
- Rashidi, Ahmad, et al.
(författare)
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Strain rate and stress fields in the West and South Lut block, Iran: Insights from the inversion of focal mechanism and geodetic data
- 2019
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Ingår i: Tectonophysics. - : Elsevier BV. - 0040-1951 .- 1879-3266. ; 766, s. 94-114
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Tidskriftsartikel (refereegranskat)abstract
- The active tectonic deformation and hazardous earthquakes in the south and west of the Lut block have been investigated for a long time. In this study, we compute the geodetic and seismic strain rates using focal mechanism data from the Harvard CMT catalogue and various other sources including the published GPS velocities. Moreover, we also perform Focal Mechanism Stress Inversion (FMSI) to deduce a stress model for the region. Our study shows an expected correlation between the stress orientations, seismic and geodetic strain rates. Our results show that the south and west of the Lut block is generally exposed as a compressional strike-slip tectonic regime. The tectonic convergence in this area is taken up not only by motions along and across the faults but also by the rotation of those blocks which bounded by these faults. The maximum amount of rotation rate is observed where there are the main right lateral strike slip fault systems such as Sabzevaran, Gowk, Nayband, Bam, Kuhbanan, and Kahurak. The orientation of the mean stress direction, obtained from the FMSI results in the west and south of the Lut block, is approximated ~N19 E. In this area, faults are almost oblique relative to the tectonic motion direction. Moreover, there are right-lateral and left-lateral shears, in addition to the dip movements in different parts of the south and west of the Lut block. Our analyses show three main categories of the stress regimes including strike-slip faulting (43.2%), thrust faulting (38.6%), and unknown or oblique faulting (18.2%).We also calculated seismic and geodetic moment rates for this area, which indicate the seismic moment rate is relatively high between Bam and Shahdad where there are some segments of the Gowk fault.
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