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Chapitre D'ouvrage Année : 2011

Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model

J. Vergne
Laurent Bollinger
Rodolphe Cattin
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Résumé

Low-velocity zones ('bright spots') imaged by the INDEPTH seismic experiment in southern Tibet are extensively interpreted as widespread partial melt within the crust, which has given a strong support for the channel flow model. These suggest that a continuous seismic low-velocity zone underlies Tibet on the large scale. Here we take advantage of the Hi-CLIMB seismic experiment which includes a dense south-north profile and a lateral 2D seismic network to assess the vertical and the horizontal extension of low-velocity zones in southern Tibet. Several approaches including migration, amplitude analysis and waveform inversion of receiver functions are performed to detect crustal low-velocity zones using this new seismological dataset. Our results reveal localized and discontinuous low-velocity zones in Tibet. They indicate that the vertical extension of the low-velocity zones is about 10 km, and their maximum horizontal length appears to be c. 50 km. Our study suggests a partial correlation between the location of these low-velocity zones and the spatial distribution of Tibetan grabens. These results, especially the non-continuity of low-velocity zones, together with the observed regular value of mean crustal VP/VS ratio, question the existence of widespread partial melt of the southern Tibetan crust and, therefore, the viability of the channel flow model.

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Dates et versions

hal-00853971 , version 1 (26-08-2013)

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Gyoergy Hetenyi, J. Vergne, Laurent Bollinger, Rodolphe Cattin. Discontinuous low-velocity zones in southern Tibet question the viability of the channel flow model. Gloaguen, R. & Ratschbacher, L. Growth and Collapse of the Tibetan Plateau, Geological Society of London, pp.99-108, 2011, Geological Society Special Publication, 353, ⟨10.1144/SP353.6⟩. ⟨hal-00853971⟩
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