Waveform Changes Due to Moving Scatterers - Application to the Inner Core
Description:
Fine-scale heterogeneity in Earth's inner core (IC) has been identified from scattering of PKIKP. The differential rotation of the IC is expected to align with Earth's rotation axis according to geodynamical modeling and seismic evidence (Wang & Vidale, EPSL 2022). For a similar differential rotation of the IC, equatorial and polar raypaths may exhibit distinct changes in scattering (Pang & Koper, 2022). Understanding the sensitivity of different raypaths to the shift of IC scatterers can facilitate our interpretation of inner core motion.
Here we perform 2D wavefield scattering simulations using the spectral-elemental toolkit Salvus. We analyze the variation of forward-scattering and back-scattering waveforms as the heterogeneity is shifted radially along and transversely across the raypath. The radial and transverse movements of heterogeneity approximately correspond to equatorial and polar raypaths sampling the IC. The back-scattering and the forward scattering geometry approximates the PKIKP raypaths with different distances.
Distinct variation patterns in the PKiKP coda are observed between the two directions of shift (heterogeneity shift is 1 cell, with RMS variations about 10%) and the two raypaths. For forward-scattering, a radial shift almost doesn't change the waveforms, whereas transverse shifts result in significant waveform variations; for the back-scattering case, a radial shift mainly delays or advances the phase, while transverse shift leads to both timing and amplitude changes. The evolution with lapse time of the waveform similarity and time shifts, also have distinct patterns, which will be discussed in detail.
Distinguishing the effect of the moving scatterers across different geometries will contribute to constraining the rotation of the IC and will provide a deeper general understanding of scattering behavior.
Session: Earth’s Structure from the Crust to the Core - III
Type: Oral
Date: 5/1/2024
Presentation Time: 02:45 PM (local time)
Presenting Author: Ruoyan
Student Presenter: Yes
Invited Presentation:
Authors
Ruoyan Wang Presenting Author Corresponding Author ruoyanw@usc.edu University of Southern California |
John Vidale jvidale@usc.edu University of Southern California |
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Waveform Changes Due to Moving Scatterers - Application to the Inner Core
Session
Earth’s Structure from the Crust to the Core