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Absolute and relative gravimetry 1990-1992-1995 in the Western Yunnan earthquake prediction experimental area / Wolfgang Torge (1999)

Public Titre : Absolute and relative gravimetry 1990-1992-1995 in the Western Yunnan earthquake prediction experimental area Type de document : Monographie Auteurs : Wolfgang Torge, Auteur ; M. Schnull, Auteur ; Ludger Timmen, Auteur ; J. Minyu, Auteur ; X. Canfei, Auteur ; L. Hui, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 1999 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 307 Importance : 48 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8587-9 Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Chine [Termes IGN] gravimètre absolu [Termes IGN] gravimètre supraconducteur [Termes IGN] gravimétrie [Termes IGN] levé gravimétrique [Termes IGN] Pékin (Chine) [Termes IGN] prédiction [Termes IGN] risque naturel [Termes IGN] séisme Index. décimale : 30.43 Travaux de géodésie physique Résumé : (Auteur) The Western Yunnan Earthquake Prediction Experimental Area (WYEPEA) has been established in the middle of the 1980's by the State Seismological Bureau (SSB) of China, in order to study the geodynamic processes occurring in this region of high seismic activity. Absolute gravimetry was introduced into the WYEPEA gravity control in 1990, within the frame of a cooperation project between the Institute of Seismology, State Seismological Bureau (ISSSB), Wuhan, and the Institut für Erdmessung (IfE), University of Hannover, Germany. Three observation campaigns were performed (1990, 1992, 1995) employing the JILAG-3 absolute gravity meter of IfE. Six absolute stations have been established in the area, and additional absolute measurements were carried out in the reference stations Beijing, Wuhan, and Kunming. Relative gravity measurements between the absolute stations served for an independent control and connect the existing GPS control network to the gravity net. In addition, a micro gravity net and a vertical gravity gradient line have been established and remeasured, in order to study local gravity variations at selected fault zones. The accuracy of the absolute gravity results is estimated to ±0.05 µms- while the repeatability is slightly better. In the local systems a relative accuracy of ±0.01 ... 0.03 µms- has been achieved. Large-scale gravity variations with time could not be detected between 1990 and 1995, but local changes due to groundwater-table variations or seismic activity may reach 0.1µms-. In the local systems small gravity changes have been found, with a certain correlation to tectonic structures. The report presents the final results of the project, especially station descriptions and gravity values for the epochs 1990, 1992, and 1995. It thus will serve as a basis for future gravity campaigns, and analyzing gravity changes which might be detected then. Numéro de notice : 57511 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=60224

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The IFE absolute gravity program "South America" 1988 - 1991 / Wolfgang Torge (1994)

Public Titre : The IFE absolute gravity program "South America" 1988 - 1991 Type de document : Monographie Auteurs : Wolfgang Torge, Auteur ; Ludger Timmen, Auteur ; R. Röder, Auteur ; M. Schnull, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 1994 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 299 Importance : 44 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8582-4 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] Argentine [Termes IGN] Brésil [Termes IGN] campagne d'observations [Termes IGN] gravimètre absolu [Termes IGN] réseau gravimétrique [Termes IGN] réseau gravimétrique local [Termes IGN] station de référence [Termes IGN] Uruguay [Termes IGN] Vénézuela Index. décimale : 30.42 Gravimétrie Résumé : (Auteur) The Institut für Erdmessung (IFE), University of Hannover, Germany, performed a large-scale gravity control survey between 1988 and 1991 in South America, in cooperation with university institutes and state agencies of the countries involved and supported by "Deutsche Forschungsgemeinschaft (DFG)" and "Institute Pan-americano de Geografia e Historia (IPGH)". This control system covers a large part of South America by establishing 22 absolute gravity stations with additional local eccenters. After a first observation campaign in Venezuela in 1988 (6 stations), a project in Brazil (7 stations), Uruguay (2 stations) and Argentina (3 stations) has been performed in 1989. A final campaign in 1991 concentrated on Argentina (3 new stations) and Uruguay (1 new station, 1 reoccupied). Three gravity stations (Sta. Elena, Brasilia, Tandil) are part of the International Absolute Gravity Basestation Network (lAGBN.set A). In addition, the stations serve as absolute gravity control for geodynamic networks in the Central and Venezuelan Andes and they improve existing national gravity networks. Numéro de notice : 28254 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=63598

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Introduction of absolute gravimetric techniques into a high-precision gracity and vertical control system in Northern Iceland / Wolfgang Torge (1992)

Public Titre : Introduction of absolute gravimetric techniques into a high-precision gracity and vertical control system in Northern Iceland Type de document : Monographie Auteurs : Wolfgang Torge, Auteur ; T. Grote, Auteur ; R.H. Roder, Auteur ; M. Schnull, Auteur ; H.G. Wenzel, Auteur Editeur : Munich : Bayerische Akademie der Wissenschaften Année de publication : 1992 Collection : DGK - B Sous-collection : Angewandte Geodäsie num. 297 Importance : 52 p. Format : 21 x 30 cm ISBN/ISSN/EAN : 978-3-7696-8581-7 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] déformation verticale de la croute terrestre [Termes IGN] gravimètre absolu [Termes IGN] Islande [Termes IGN] réseau altimétrique local [Termes IGN] réseau gravimétrique [Termes IGN] système de référence géodésique [Termes IGN] volcan Index. décimale : 30.43 Travaux de géodésie physique Résumé : (Auteur) Since 1938 gravity measurements were carried out in northern Iceland to investigate the tectonic process connected with the diverging of the Eurasian and the North American Plate. This paper describes the measurements performed by Institut für Erdmessung, Universität Hannover in 1985 and 1987/88. In the last epoch 1987/88, the absolute gravimeter JILAG-3 was first employed in order to contribute to the gravimetric datum and to overcome the calibration problem being inherent to the relative gravimetric technique. The detail survey in 1985 and 1987 was carried out using four to six LaCoste&Romberg gravimeters. By establishing four absolute stations in the control area in northern Iceland, and one in Reykjavik, the absolute gravity datum and the linear calibration could be verified on the 0.05 to 0.1 µms-2 and the 1-10-4 level, respectively. The mean relative network accuracy in 1985 (with respect to a constrained base station) and the mean absolute accuracy in 1987/88 is estimated to be ±0.06 /µms-2. As in former surveys, gravimetry was supplemented by geometric leveling. The tectonic activity in the Krafia fissure zone of northern Iceland has remarkably decreased in the beginning of the 1980's. The results of the 1985 and 1987/88 surveys indicate that the minor tectonic event which occurred in 1984 together with lava outflow, caused small variations with a range of about 20 km around the Krafia central volcano, reaching maximum changes of 0.4 µms-2 in gravity and 0.2 m in height compared to the 1980/81 surveys. The general tendency, gravity increase and subsidence in the activity center (Namafjall/Krafla area), and correlated gravity decrease and uplift at the flanks, is still visible. Numéro de notice : 30656 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Monographie Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=56853

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