HR: 1330h
AN: S32A-0831    [PDF]
TI: Lithospheric Velocity Structure of the Upper Rhine Graben; A new Model for the Development of Europe's Largest Continental Rift.
AU: * Granet, M
EM: Michel.Granet@eost.u-strasbg.fr
AF: Universite Louis Pasteur, EOST - IPG Strasbourg UMR CNRS/ULP 7516 5 rue Rene Descartes, Strasbourg, 67084 France
AU: Lopes Cardozo, G
EM: gideon@danube.u-strasbg.fr
AF: Universite Louis Pasteur, EOST - IPG Strasbourg UMR CNRS/ULP 7516 5 rue Rene Descartes, Strasbourg, 67084 France
AU: Herquel, G
EM: Georges.Herquel@eost.u-strasbg.fr
AF: Universite Louis Pasteur, EOST - IPG Strasbourg UMR CNRS/ULP 7516 5 rue Rene Descartes, Strasbourg, 67084 France
AB: The lithospheric structure of the Rhine Graben, part of the European Cenozoic Rift system (ECRIS), is studied with the help of a regional 3D teleseismic travel time tomography. Joint interpretation of the tomography, the SKS anisotropy, and a local earthquake tomographic study leads to a new model for the rifting and development of the Graben. Two seismic campaigns provided 2696 P and PKP travel time residuals of teleseismic events. The two data sets are combined and inverted together. This inversion yields detailed images of the P velocity structure of the lower crust and the lithospheric mantle down to a depth of 125 kilometers. An absence of strong low velocity anomalies in the region confirms that there is no shallow mantle diapir, this demonstrates the passive development of the rift. The observed velocity structures have an orientation 10$\deg$-20$\deg$ oblique to the graben axis and are interpreted as inherited Variscan structures. These structures are thought to have played a dominant role during the Oligocene rifting of the Rhine Graben. Similar structures are known to have influenced the development of the Limagne graben (Massif Central), also part of the ECRIS. An absence of structures that are orientated parallel to the graben axis shows that the Upper Rhine Graben did not form following a traditional McKenzie or Wernicke model. A new model is presented in which strike slip movements on the Variscan structures in the lithospheric mantle are responsible for the extension in the crust. This conceptual model is supported by SKS anisotropy and helps to explain some of the features in the development of the continental rift in the overall compressive setting of the Alpine foreland.
UR: http://eost.u-strasbg.fr
DE: 7200 SEISMOLOGY
DE: 7218 Lithosphere and upper mantle
DE: 7230 Seismicity and seismotectonics
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8180 Tomography
SC: Seismology [S]
MN: 2003 Fall Meeting