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WITHDRAWN A New Constraint on Vp and Vs in the Uppermost Mantle From Late Coda

WITHDRAWN The Preliminary Reference Earth Model (PREM) is a widely used seismic reference model in seismology. However, global SS-S and PP-P differential travel times have bimodal ocean/continent distributions with mean values of +3 s of both PP-P and SS-S. This suggests that PREM represents the seismic structure of the continental upper mantle better than the oceanic upper mantle and that, on average, PREM overpredicts the P-wave (v_p) and S-wave (v_s) velocities in the upper mantle.

PP-P and SS-S can be influenced by deep mantle structure, especially when P and S waves propagate through D’’. It is therefore important to find independent constraints on v_p and v_s in the upper mantle. We explore P-wave reverberations in the mantle contained in the six-hour long segment of a vertical-component seismogram following the major-arc Rayleigh wave. We detect top-side reflections (i.e., p410s and p410p) off the 410-km discontinuity in stacks of cross-correlated “late coda” from 83 large earthquakes recorded by the Southern California Seismic Network. The lag time between p410s and p410p is about 39 s for an inter-station distance of 100 km. Together with PP-P and SS-S, we estimate that v_s and v_p in the uppermost 200 km of the mantle are 1% and 5% lower than in PREM, respectively. This is an important constraint for tomographic studies of Earth’s upper mantle, especially studies focused on horizontal v_p variations and radial anisotropy.

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

Type: Oral

Room: Key Ballroom 9

Date: 4/16/2025

Presentation Time: 05:15 PM (local time)

Presenting Author: Meichen Liu

Student Presenter: No

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