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GPS coordinate time series measurements in Ontario and Quebec, Canada / Hadis Samadi Alinia in Journal of geodesy, vol 91 n° 6 (June 2017)  

Public [article]  inJournal of geodesy > vol 91 n° 6 (June 2017) . - pp 653 - 683 Titre : GPS coordinate time series measurements in Ontario and Quebec, Canada Type de document : Article/Communication Auteurs : Hadis Samadi Alinia, Auteur ; Christy F. Tiampo, Auteur ; Thomas S. James, Auteur Année de publication : 2017 Article en page(s) : pp 653 - 683 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Systèmes de référence et réseaux [Termes IGN] Bernese [Termes IGN] bruit (théorie du signal) [Termes IGN] bruit blanc [Termes IGN] champ de vitesse [Termes IGN] coordonnées GPS [Termes IGN] épaisseur de la glace [Termes IGN] Hudson, baie d' [Termes IGN] méthode du maximum de vraisemblance (estimation) [Termes IGN] Ontario (Canada) [Termes IGN] Québec (Canada) [Termes IGN] série temporelle [Termes IGN] station permanente Résumé : (Auteur) New precise network solutions for continuous GPS (cGPS) stations distributed in eastern Ontario and western Québec provide constraints on the regional three-dimensional crustal velocity field. Five years of continuous observations at fourteen cGPS sites were analyzed using Bernese GPS processing software. Several different sub-networks were chosen from these stations, and the data were processed and compared to in order to select the optimal configuration to accurately estimate the vertical and horizontal station velocities and minimize the associated errors. The coordinate time series were then compared to the crustal motions from global solutions and the optimized solution is presented here. A noise analysis model with power-law and white noise, which best describes the noise characteristics of all three components, was employed for the GPS time series analysis. The linear trend, associated uncertainties, and the spectral index of the power-law noise were calculated using a maximum likelihood estimation approach. The residual horizontal velocities, after removal of rigid plate motion, have a magnitude consistent with expected glacial isostatic adjustment (GIA). The vertical velocities increase from subsidence of almost 1.9 mm/year south of the Great Lakes to uplift near Hudson Bay, where the highest rate is approximately 10.9 mm/year. The residual horizontal velocities range from approximately 0.5 mm/year, oriented south–southeastward, at the Great Lakes to nearly 1.5 mm/year directed toward the interior of Hudson Bay at stations adjacent to its shoreline. Here, the velocity uncertainties are estimated at less than 0.6 mm/year for the horizontal component and 1.1 mm/year for the vertical component. A comparison between the observed velocities and GIA model predictions, for a limited range of Earth models, shows a better fit to the observations for the Earth model with the smallest upper mantle viscosity and the largest lower mantle viscosity. However, the pattern of horizontal deformation is not well explained in the north, along Hudson Bay, suggesting that revisions to the ice thickness history are needed to improve the fit to observations. Numéro de notice : A2017-287 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1007/s00190-016-0987-5 En ligne : http://doi.org/10.1007/s00190-016-0987-5 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=85320 [article]

Short-term surface deformation on the Northern Hayward Fault, CA, and nearby landslides using polarimetric SAR interferometry (PolInSAR) / Samira Alipour in Pure and applied geophysics, vol 172 n° 8 (August 2015)  

Public [article]  inPure and applied geophysics > vol 172 n° 8 (August 2015) . - pp 2179 - 2193 Titre : Short-term surface deformation on the Northern Hayward Fault, CA, and nearby landslides using polarimetric SAR interferometry (PolInSAR) Type de document : Article/Communication Auteurs : Samira Alipour, Auteur ; Christy F. Tiampo, Auteur ; Sergey V. Samsonov, Auteur ; Pablo J. González, Auteur Année de publication : 2015 Article en page(s) : pp 2179 - 2193 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Traitement d'image radar et applications [Termes IGN] Californie (Etats-Unis) [Termes IGN] faille géologique [Termes IGN] image Radarsat [Termes IGN] optimisation (mathématiques) [Termes IGN] polarimétrie radar [Termes IGN] risque naturel Résumé : (auteur) In this study, we analyze 25 RADARSAT-2 images from ascending and descending geometries to study the creep rate on the Hayward fault and landslide motions near Berkeley, CA. We applied a coherence optimization technique from polarimetric synthetic aperture radar interferometry (PolInSAR) to increase the accuracy of the measurements. We resolve 3–5 mm/year of motion along the Hayward fault, in agreement with earlier creep estimates. We identify a potential motion on secondary fault, northeast and parallel to the Hayward fault, which is creeping at a lower rate of ~1.5 mm/year. In addition, we identify a number of landslides along the hills east of the fault that agree with earlier results from advanced interferometric synthetic aperture radar (SAR) analysis and field investigations. We investigate four particular slope instabilities, one of which was marked as moderately active, and three as highly active, by earlier field investigations. The resolved along-hill slope displacement is estimated at ~23 mm/year. Our results demonstrate that PolInSAR is an effective method to increase the interferometric coherence and provide improved resolution of deformation features associated with natural hazards. Numéro de notice : A2015-492 Affiliation des auteurs : non IGN Thématique : IMAGERIE Nature : Article DOI : 10.1007/s00024-013-0747-x Date de publication en ligne : 10/12/2013 En ligne : https://doi.org/10.1007/s00024-013-0747-x Format de la ressource électronique : url article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=77287 [article]