Lecture by Martyn Unsworth, Professor of Physics on 2008 Sichuan Earthquake

17 March 2014

Topic: Tectonics of the India-Asia collision: Did crustal flow contribute to the 2008 Sichuan earthquake?

Speaker: Martyn Unsworth, Professor of Physics / Earth and Atmospheric Sciences, University of Alberta

Time: Noon, Friday March 21

Location: Tory 3-36

Abstract:

The Tibetan Plateau was formed by the collision between India and Asia and is the type example of a continent-continent collision. It has been studied extensively over the last 20 years to determine how the crust responds to these collisions, which have occurred throughout the geological record as the continents were assembled. Integrated studies using geological and geophysical data have shown that partial melting can often occur in crust during collisions. This causes significant weakening of the crust and has a very strong influence on the rheology and style of deformation.

In this talk I will summarize the magnetotelluric data from Tibet and discuss how it has defined the pattern of crustal flow observed beneath the Himalaya and Southern Tibet. I will also show new data from Eastern Tibet give new insights into how the crust is being extruded to the southeast in response to the ongoing collision.

The 2008 Sichuan earthquake occurred on the eastern margin of the Tibetan Plateau and was directly caused by crustal motion due to the India-Asia collision. Some aspects of this earthquake can be explained by the hypothesis of crustal flow being blocked by the stable lithosphere of the Sichuan Basin.

New magnetotelluric data give support to this theory and will be presented. In addition to presenting new scientific results, I will also show a number of photographs taken on recent field trips in southwest China, including visits to the area devastated by the 2008 Sichuan earthquake.