Presented By: Michigan Institute for Computational Discovery and Engineering
MICDE Ph.D. Student Seminar: Meichen Liu
Meichen Liu, PhD candidate in Earth & Environmental Sciences and Scientific Computing
Topic: Influence of shear wave velocity heterogeneity on SH-wave reverberation imaging of the mantle transition zone
We use the top-side shear wave reflection Ssds as a probe for mapping the depths of the mantle transition zone (MTZ) beneath the contiguous US. Using a common-reflection point (CRP) mapping approach, we observe that the MTZ are about 40–50 km deeper beneath the western United States than the central-eastern United States if based on the 1-D Earth wave velocity model (Preliminary Reference Earth Model). However, the east-to-west deepening of the MTZ disappears in the CRP image if we account for 3-D shear wave velocity variations in the mantle according to global tomography. In addition, from spectral-element method synthetics, we find that ray theory overpredicts the traveltime delays of the reverberations. Undulations of the MTZ are underestimated when their wavelengths are smaller than the Fresnel zones of the wave reverberations in the MTZ. Therefore, modelling of layering in the upper mantle must be based on 3-D reference structures and accurate calculations of reverberation traveltimes.
We use the top-side shear wave reflection Ssds as a probe for mapping the depths of the mantle transition zone (MTZ) beneath the contiguous US. Using a common-reflection point (CRP) mapping approach, we observe that the MTZ are about 40–50 km deeper beneath the western United States than the central-eastern United States if based on the 1-D Earth wave velocity model (Preliminary Reference Earth Model). However, the east-to-west deepening of the MTZ disappears in the CRP image if we account for 3-D shear wave velocity variations in the mantle according to global tomography. In addition, from spectral-element method synthetics, we find that ray theory overpredicts the traveltime delays of the reverberations. Undulations of the MTZ are underestimated when their wavelengths are smaller than the Fresnel zones of the wave reverberations in the MTZ. Therefore, modelling of layering in the upper mantle must be based on 3-D reference structures and accurate calculations of reverberation traveltimes.
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ZoomDecember 1, 2022 (Thursday) 4:00pm
Meeting ID: 92999972518
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