PUBLIC LECTURE: Where the stressed Earth fails: The Himalayan syntaxes

A public lecture by Professor Jean-Pierre Burg, Institute of Geology, ETH Zurich 2012 UWA Gledden Visiting Senior Fellow.

The Himalayan syntaxes, at the western and eastern extremities of the Himalaya Mountain Range, are anomalously high regions around which the mountain trends turn by nearly 180°. Geological evidence shows that both syntaxes are crustal-scale folds rose over the last 4 Ma. Concurrent erosion has dug out the rocks that were 30 km deep in the core of these mountains. Rapid exhumation of the deep crustal levels is caused by c. 10 mm a year erosion coeval with crustal scale folding, a rare mode of crustal failure under high stress and shortening rate. The eastern syntaxes, called Namche Barwa, after the central, nearly 8000 m high mountain, is traversed by the Tsangpo River, known as the Brahmaputra downstream, which has followed the trace of the India-Asia Suture for over 1300 km from its source to the doorway of the fold. The cooling history of the exposed deep rocks documents that the antecedent river has been displaced and folded by the growing antiform in which is carved the deepest canyon worldwide. Numerical modeling shows that high stressed syntaxes like in the Himalayas lead to nucleation of first-order thrust faults.This process offers an insight on the formation of major thrust systems that extend over several thousand kilometers along the Himalayan mountain system, and along which several > magnitude 8 earthquakes took place over the last century.

This lecture will examine the geological structure and geodynamic situation of Himalayan syntaxes and discuss the processes responsible for generation of earthquakes in this vulnerable region.

Cost: Free, no RSVP required.