Plate tectonics is characterized by rigid, moving landforms, or plates, which cover Earth's surface. The motion of these plates fundamentally alters the landscape of the planet. Moreover, plate motions are primarily responsible for earthquakes, tsunamis, and many other natural hazards. The driving force for this plate motion is the slow convection of Earth's mantle. A fundamental problem in geophysics is understanding the flow patterns of mantle convection, and how they interact with moving plates. To infer these flow patterns, we use the tools of seismology to detect structures in Earth's interior that are produced by the deformation of rocks. The objective of the proposed research is to investigate details of how we infer flow patterns from seismological data.
Dense seismic networks and high resolution measurements of seismic anisotropy provide new opportunities for insight into mantle deformation, particularly in the vicinity of plate boundaries. However, to interpret seismic anisotropy in terms of flow patterns the relationship between seismic anisotropy and deformation kinematics must be understood. Most seismic anisotropy is generated by the lattice-preferred orientation (LPO) of olivine, which forms and evolves in response to progressive deformation. The pattern and rate of evolution depends on the physiochemical conditions of deformation, and its effects on microphysical deformation and recovery. In these projects, we are investigating several factors, including the role of (1) temperature, (2) grain-size, and (3) pre-existing LPO, on texture development. Our primary focus will be on the mineral olivine, which produces most of the seismic anisotropy in the upper mantle. We will conduct experiments to understand the sensitivity of microstructural evolution to different laboratory conditions and to facilitate extrapolation to Earth. Data collected in these experiments will provide a new context for the interpretation of seismic anisotropy, especially in complex kinematic settings.
