Seismic imaging of crust-mantle interaction

点击翻译按钮获取中文摘要

The large-scale processes governing the evolution of the Earth's surface and its deep interior are fundamentally different: the crust undergoes plate tectonics, while the mantle overturns through thermal convection. My proposed research program will examine how these two processes are coupled, particularly in the case of thick continental plates. The continental lithosphere, a ca. 250 km thick layer of mantle material, participates in plate-tectonic motions, but is also eroded by thermal plumes arising from the deep mantle. I propose to examine the lithosphere beneath the Canadian Shield for both crustal and mantle influences, using passive seismic imaging techniques. These techniques involve recording seismic waves produced by earthquakes at networks of seismometers deployed over the study area, and then mathematically reconstructing the properties of the material through which the waves were transmitted. My planned field experiments will be focused on Manitoba, Saskatchewan, and western Ontario, and will target the edge of the ancient Superior continent, the former Trans-Hudson mountain belt lying beneath Saskatchewan, and a billion-year-old rift zone underlying Lake Superior. For all of these structures, I intend to examine the extent to which the geology of the crust is reflected within the lithosphere below. I will also contribute to the development of new methods for producing images of Earth structure from seismic waves: in particular, the use of seismic noise recordings in structural imaging, and the use of scattered and deflected waves travelling along the Earth's surface. This work will contribute to a better understanding of the forces acting on continental plates, along with the deformation history of these plates. I thereby expect to help establish a framework for understanding the large-scale processes that have preserved or deformed ancient continental crust, and the specific history and dynamics of the Canadian Shield. As the lithosphere beneath ancient shield regions is known to be a source region for diamonds, better images of the lithosphere beneath the Canadian Shield will also assist in future diamond exploration.