Hem Bahadur Motra

How Important is Compositional Layering within the Earth? Testing the Hypothesis using Seismic Anisotropy

Seismological observations indicate that large regions within Earth show directionally dependent seismic wave speeds. Such seismic anisotropy is a unique and invaluable indicator for geodynamic processes, structure and rheology of the Earth. However, a challenge in using anisotropy is that it arises from different sources, leading to non-unique interpretations of the geodynamic process that give rise to anisotropy. Intrinsic anisotropy originates from single crystals, or aggregates of oriented crystals, which is known as crystallographic preferred orientation (CPO). It is an important source for anisotropy in the deeper parts of the crust, mantle and core. Extrinsic, or apparent, anisotropy arises from geometrical effects such as layering of rocks, and oriented crack and fluid networks. In this project, particular focus is placed on testing the hypothesis that mineral compositional banding is an important contributor to seismic anisotropy throughout the interior of Earth, which has not