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Updating for two recent earthquakes in California / C Pearson in SaLIS Surveying and land information science, vol 67 n° 3 (October 2007)

Public [article]  inSaLIS Surveying and land information science > vol 67 n° 3 (October 2007) . - pp 149 - 158 Titre : Updating for two recent earthquakes in California Type de document : Article/Communication Auteurs : C Pearson, Auteur ; R. Snay, Auteur Année de publication : 2007 Article en page(s) : pp 149 - 158 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Navigation et positionnement [Termes IGN] Californie (Etats-Unis) [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] positionnement par GPS [Termes IGN] risque naturel [Termes IGN] séisme [Termes IGN] traitement de données GNSS Résumé : (Auteur) This paper describes revisions to the Horizontal Time Dependent Positioning (HTDP) software carried out to address the motion associated with two recent California earthquakes. NOAA's National Geodetic Survey (NGS) developed HTDP to enable its users to compensate survey measurements for the differential movement associated with tectonic deformation, so that surveys conducted at different epochs may be compared. We focus on the process of selecting and validating models for two recent earthquakes in California, prior to their inclusion in version 2.9 of this software (HTDP v2.9) the Parkfield earthquake with a magnitude of 6.0, which occurred on September 28, 2004, and the San Simeon, California earthquake with a magnitude of 6.5, occurring on December 22, 2003. The process of modeling and correcting for deformation can be well illustrated by utilizing data collected in the vicinity of these earthquakes, because they represent contrasting styles of deformation Parkfield exhibited strike-slip motion and San Simeon wax predominantly a blind-thrust earthquake. Also, while both earthquakes were relatively small, they produced significant displacements (though restricted to a relatively small area in central California). The Parkfield earthquake, in particular, produced an unusually high proportion of post-seismic deformation. This deformation can accumulate during a period of a few months after the earthquake, whereas co-seismic deformation occurs suddenly during an earthquake. Quantifying and characterizing deformation at these disparate time scales represents a major challenge to developing the accurate models of deformation that are required to support modern, high-accuracy surveying in tectonically active areas such as California. This study also confirms the importance of including separate dislocation models of the co-seismic and post-seismic deformation, because, as was the case for Parkfield, post-seismic deformation can be comparable in magnitude to co-seismic deformation. Copyright SaLIS Numéro de notice : A2007-590 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=83657 [article]

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Reducing the profile of sparse symmetric matrices / R. Snay (ca : 1976) 

Public Titre : Reducing the profile of sparse symmetric matrices Type de document : Article/Communication Auteurs : R. Snay, Auteur Editeur : [s.l.] : [s.n.] Année de publication : ca : 1976 Importance : 24 p. Format : 21 x 30 cm Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Analyse numérique [Termes IGN] matrice creuse [Termes IGN] matrice symétrique Résumé : (Auteur) An algorithm for improving the profile of a sparse symmetric matrix is introduced. Tests on normal equation matrices encountered in adjustments of geodetic networks by least squares demonstrate that the algorithm produces significantly lower profiles than the widely used reverse Cuthill-McKee algorithm. Numéro de notice : 13603 Affiliation des auteurs : non IGN Thématique : MATHEMATIQUE Nature : Plaquette / brochure Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=62553

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