Seismic Signatures of Inner Core Solidification

点击翻译按钮获取中文摘要

The deep interior of Earth, revealed by seismic waves, affects processes at the surface of our planet. Among these is the solidification of Earth's inner core from the liquid iron of its outer core. Variations in this solidification, detected from seismic waves, will be helpful in understanding and predicting variations in our magnetic field that can affect our atmosphere and surface life. This project seeks to map the solidification of Earth's inner core using seismic waves reflected and transmitted through it. Education and training will be provided to graduate students in computation, digital data retrieval and processing, and structural imaging from any wave-like phenomena. These skills are transferable to broad areas of science and engineering, including resource exploration, computational science, and medical imaging. Results will be incorporated in undergraduate introductory courses to encourage recruitment and retention of students across STEM fields. Results will also be regularly shared with public media having interests in earthquakes and planetary science.Transitions in the elastic structure beneath the Inner Core Boundary (ICB), including their effects on lateral variations in elastic waves speeds, body waveform complexity and attenuation and the depth onset of elastic anisotropy are important for understanding the process of compositional convection. This process has been favored as the mechanism that currently sustains our magnetic field through the crystallization and the buoyant rise of light elements as the inner core solidifies. Unique elements of the proposed activity include separating the effect of earthquake sources on waveforms to improve estimates of inner core attenuation, evaluating the relative contributions of attenuation by forward scattering and intrinsic attenuation, relating small- scale heterogeneity to a solidification fabric and elastic anisotropy, and exploiting the use of a body wave having high sensitivity to the shear velocity structure beneath the inner core boundary.