Empirical analysis of complex wavefields

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The principal focus of this thesis is exploring the passive seismic wavefield, including both ambient seismic noise and earthquake ground motion. On the one hand, ambient noise, though appearing to be a nuisance and treated as an unwanted component, has seen flourishing applications in the past decades. However, the discrepancy between the reality of noise properties and theoretical assumptions leads to considerable bias in those applications. A better understanding of the noise wavefield is therefore crucial. One the other hand, significant earthquakes pose continuous threats to human life and habitat. Mitigating seismic hazard demands detailed knowledge of these seismic waves that carry tremendous energy and cause damage. In this thesis, I first give a background introduction on seismic wavefields and the connection between seismic noise and earthquake ground shaking. Then I demon- strate that it's possible to convert the noise data into signals, which can be used to simulate long-period earthquake ground motion. I introduce an improved multi-component C3 method. It enhances the signal-to-noise ratio of the simulation and yields more reliable amplitude estimates. Starting from a puzzling observation, I carefully examine the C3 method and propose a new interpretation of it. Inspired by this insight, I develop a modified signal processing procedure that increases the resolving power of traditional seismic interferometry techniques on relatively sparse networks. I then switch the focus to the coda of repeating earthquakes, which are used to extract velocity perturbations. Studying earthquake coda provides insights into the coda of correlations. The chapter following focuses on the spatial variability of earthquake ground motions by exploring the similarity of earthquake recordings on dense seismic arrays. The spatial coherence revealed from waveform similarity is consistent with that from amplitude measurement


Type of resource text
Form electronic resource; remote; computer; online resource
Extent 1 online resource
Place California
Place [Stanford, California]
Publisher [Stanford University]
Copyright date 2020; ©2020
Publication date 2020; 2020
Issuance monographic
Language English


Author Sheng, Yixiao
Degree supervisor Beroza, Gregory C. (Gregory Christian)
Thesis advisor Beroza, Gregory C. (Gregory Christian)
Thesis advisor Baker, Jack W
Thesis advisor Ellsworth, William L
Degree committee member Baker, Jack W
Degree committee member Ellsworth, William L
Associated with Stanford University, Department of Geophysics.


Genre Theses
Genre Text

Bibliographic information

Statement of responsibility Yixiao Sheng
Note Submitted to the Department of Geophysics
Thesis Thesis Ph.D. Stanford University 2020
Location electronic resource

Access conditions

© 2020 by Yixiao Sheng
This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).

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