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Imaging of the Global Oceanic Lithospheric Structure With Probabilistic Deconvolution of SS Waves

Description: 

Previous studies using the SS precursor technique mostly target the mantle transition zone by applying a narrow bandpass filter with long periods to the time-domain waveforms and interpreting seismic structures directly from the waveform stacks. While this treatment has been proven successful when targeting various mantle structures, alternate data processing methods are required when investigating lithospheric structures because the effect of these shallow seismic discontinuities is usually non-separable from the main SS phase. In this study, we propose to image the lithospheric structure by the deconvolution of SS waves using a transdimensional probabilistic Bayesian inference. The signature of seismic discontinuities is characterized by a reflectivity series consisting of an unknown number of Gaussian pairs, the time delay, amplitude, and width of which represent the depth, velocity difference, and gradient of the discontinuities. We also invert for noise parameters simultaneously in the Bayesian process, using a reversible-jump Markov-chain Monte Carlo (rj-McMC) implementation. Synthetic tests show that our approach can effectively recover the lithospheric operators for both single-discontinuity and multi-discontinuity models even when realistic background noise is present. In real data experiments, we propose to use the Hilbert transform of the direct S phase as the reference waveform in the deconvolution, as it resembles the shape of the SS arrival but does not carry information about the structures at the bounce point. Preliminary results from the NoMelt region southeast of Hawaii in the normal Pacific Ocean resolve a consistent seismic LAB (lithosphere-asthenosphere boundary) structure across different chains, showing promising potential for accurately imaging lithospheric structures using the proposed approach. We anticipate our approach will enable high-resolution lithospheric imaging, especially in the global oceans where seismic stations are sparsely deployed.

Session: ESC-SSA Joint Session:Seismology in the Global Oceans: Advances in Methods and Observations [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Ziqi

Student Presenter: No

Invited Presentation: 

Poster Number: 6

Authors