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Published November 15, 2001 | public
Journal Article

Le cycle sismique en Himalaya

Abstract

We discuss the seismic cycle in the Himalayas and its relation to mountain building on the basis of geodetic, seismological and geological data collected in the Himalaya of Nepal. On average over several seismic cycles, localized slip on a major thrust fault, the Main Himalayan Thrust fault, MHT, accommodates the ∼21 mm·yr^(−1) convergence rate between southern Tibet and India. The geodetic data show that the MHT is presently locked from the sub-Himalayas to beneath the front of the high range where it roots into a sub-horizontal ductile shear zone under southern Tibet. Aseismic slip during the interseismic period induces stress accumulation at the southern edge of this shear zone triggering intense microseismic activity and elastic straining of the upper crust at the front of the high range. This deformation is released, on the long term, by major earthquakes on the MHT. Such an event is the M_w 8.4-1934-earthquake that ruptured a 250–300-km long segment. The major seismic events along the Himalayas since the 19th century have released more than 70% of the crustal strain accumulated over that period, suggesting that, if any, aseismic slip on the MHT cannot account for more than 30% of the total slip.

Additional Information

© 2001 Académie des sciences, Éditions scientifiques et médicales Elsevier SAS. Nous sommes reconnaissants à J. Angelier et à P. Tapponnier de nous avoir invités à rédiger cet article ainsi que des commentaires qu'ils nous ont apportés. Nous remercions le CEA pour le soutien au programme mené en collaboration avec le Département des mines et de la géologie du Népal, du cadre duquel sont issus les résultats présentés ici. Nous devons beaucoup à MM. Pandey, Tandukar, Chitrakar, à toute l'équipe du Seismic Centre (DMG) ainsi qu'à toutes les personnes qui, au CEA/DAM, ont contribué à cette collaboration dont T. Héritier, J.-P. Massot, A. Mesteers et Y. Caristan. Merci à F. Guillois pour la mise en forme des figures.

Additional details

Created:
August 21, 2023
Modified:
October 18, 2023