Structure and motion of the inner core from dense arrays

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The inner core, the 1000-km-radius solid metal ball at the center of Earth embedded in the liquid metal outer core, is a subject of fundamental interest and public fascination. The freezing of the outer core to build the inner core powers Earth’s magnetic field and so refinement of inner core structure and motion will shed light on the convective geodynamo in the outer core and thus the generation of the fluctuating magnetic field, which has affected evolution and protects life on Earth. This project will focus several large arrays of seismometers to image the fine structure in the inner core in an effort to deepen our understanding of its processes. This award will support a graduate student and post doctoral scholar, and includes international collaboration.Earth’s inner core (IC) is a central but poorly understood frontier. Understanding its structure, motion, and history all pose formidable challenges. Temporal changes and roughly hemispherical structure of seismic velocity variation, anisotropy, thickness of the upper isotropic layer, and attenuation have been estimated, yet interpretation of these observations has so far been incomplete and often contradictory. The investigators will use refined beam-forming techniques, applied to 1970s data from the Large Aperture Seismic Array (LASA), the modern Hi-Net and China Arrays (CHArray), and several smaller arrays to explore the distribution of fine-scale IC heterogeneity. The proponents aim to beam-form with dense arrays to map and characterize IC regions with strong heterogeneity to interpret the structures and track their motion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.