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Illuminating Earth’s Inner Core Fine-Scale Heterogeneity With Small Aperture Arrays

Description: 

The Earth's inner core is seismically heterogeneous at scales of 1–10 km. The fine-scale heterogeneity is manifested in high-frequency (1–4 Hz) backscattered energy following reflections (PKiKP) from the inner core boundary and is very difficult to observe, resulting in a lack of a comprehensive probe. In this study, we utilize small-aperture seismic arrays—designed to detect tiny signals from underground nuclear explosions—to characterize the inner core heterogeneity in a global scale. We use all the viable data from earthquakes (Mw ≥ 5.7) within the past 2–3 decades recorded at distances of 50°–75° from an array. With array processing, we develop a framework for detection and extraction of the inner core scattered energy, which is characterized as emergent, growing, and spindle-shaped PKiKP coda. We found that individual seismic traces lacking clear evidence of PKiKP coda waves reveal the scattering characteristics when stacked together, implying the inner core scattering is ubiquitous. Furthermore, we employ a modified phonon-based simulation to model the scattering strength to construct the first global three-dimension inner core heterogeneity model. Our model shows the scattering strength substantially increases 500–800 km beneath the inner core boundary across the globe. The enhanced scattering implies an irregular solidification evolution of Earth’s core.

Session: Earth’s Structure from the Crust to the Core - III

Type: Oral

Date: 5/1/2024

Presentation Time: 02:30 PM (local time)

Presenting Author: Sin-Mei

Student Presenter: No

Invited Presentation: Yes

Authors