22nd
Himalaya-Karakoram-Tibet Workshop
Hong Kong, May 2007
Abstract Submission Template
A new
seismological experiment to constrain the lithospheric structure across the
Longmen Shan
Jérôme VERGNE 1, Jieshou
ZHU 2, Alexandra ROBERT 1, Manuel PUBELLIER 1,
Gérard WITTLINGER 3
1 Laboratoire de
géologie, Ecole Normale Supérieure, 24 rue Lhomond, 75231 Paris, FRANCE
2 Earth Science Key
Laboratory, Chengdu University of Technology, Chengdu, CHINA
3 Ecole et
Observatoire des Sciences de
Our knowledge
about the formation, the evolution and the dynamic of the Tibetan plateau is
deeply linked to the results obtained through numerous seismological campaigns
since more than 20 years. These experiments yield major informations about the
structure and the composition of the crust and upper mantle in central Tibet,
as well as along its southern, western and northeastern borders. However, very
few is known about the lithospheric structure of the eastern border of the
plateau, constituted by the Longmen Shan belt that separates the plateau from
the Yang Tse craton. It is however a key zone to understand the strain regime
linked to the India-Asia collision on the plateau's borders.
In the framework
of a collaboration between several French institutes and the Chengdu University
of Technology, a temporary network of 36 seismological stations has been
deployed in the central part of the Longmen Shan belt from November 2005 to
April 2007. The network is mostly constituted by a dense line of stations, with
a mean inter-station of about
The mains
objectives of this experiment were 1) to determine variations in crustal
thickness across the belt, 2) to precise the crustal structure and composition,
especially to test the existence of a mid-crustal low viscosity channel 3) to
better constrain the mechanism of the extrusion of the tibetan upper-mantle
toward the east.
Here, we present
in detail this experiment, the objectives, and the preliminary results deduced
from the data already processed.