Upper-mantle water stratification inferred from observations of the 2012 Indian Ocean earthquake

November 7, 2016

In 2012, a large earthquake occurred in the Indian Ocean that cut the entire oceanic lithosphere (rigid plate). This is an unusual earthquake, and because the fault plane goes so close to the lithosphere-asthenosphere boundary (LAB), the data on deformation after this earthquake provide rare opportunity to study the structure of the LAB.

Scientists at Earth Observatory of Singapore (in Nanyang Technology University, Singapore) measured deformation after this earthquake using GPS. Shun Karato at Yale initiated a collaboration with scientists in Earth Observatory of Singapore including Sagar Masuti and Sylvain Barbot to determine the structure of the oceanic lithosphere-asthenosphere boundary based on the geodetic observations after this earthquake. The results were published in Nature (October 20, 2016) showing that water content is stratified (water-poor lithosphere and water-rich asthenosphere) at ~60-70 km depth and that the viscosity of the asthenosphere is on the order of 1018 Pa s. A collaboration with these scientists is continuing and we investigate both the fault dynamics and the viscous flow in the mantle.