ERA

Download the full-sized PDF of Imaging Upper Mantle Discontinuities Using Long Period Seismic DataDownload the full-sized PDF

Analytics

Share

Permanent link (DOI): https://doi.org/10.7939/R3CR5NR0G

Download

Export to: EndNote  |  Zotero  |  Mendeley

Communities

This file is in the following communities:

Graduate Studies and Research, Faculty of

Collections

This file is in the following collections:

Theses and Dissertations

Imaging Upper Mantle Discontinuities Using Long Period Seismic Data Open Access

Descriptions

Other title
Subject/Keyword
SS precursors
Subduction Zones
Waveform Inversion
Migration Imaging
Signal Processing
Mantle Transition Zone
Type of item
Thesis
Degree grantor
University of Alberta
Author or creator
Mohammad Hosseini Dokht, Ramin
Supervisor and department
Gu, Yu Jeffrey (Physics)
Examining committee member and department
Sacchi, Mauricio D (Physics)
Kravchinsky, Vadim (Physics)
Li, Aibing (Earth and Atmospheric Sciences, University of Houston)
Kavanaugh, Jeffrey (Earth and Atmospheric Sciences)
Schmitt, Doug (Physics)
Department
Department of Physics
Specialization
Geophysics
Date accepted
2017-01-20T11:02:40Z
Graduation date
2017-06:Spring 2017
Degree
Doctor of Philosophy
Degree level
Doctoral
Abstract
Mantle reflectivity structure provides critical information on the temperature and composition of the mantle. So far, these structures are obtained by independent analyses of amplitudes and timing information of reflected and converted seismic phases at mantle discontinuities. These approaches are limited due to their inherent trade-off between velocity and gradient zone depth. This thesis aims to provide high resolution, novel imaging methods based on a nonlinear inversion method and wave spectral characteristics. Substantially improved data constraints, combined with increased imaging resolution and accuracy from this thesis, offer new insights into the process and effects of subduction (both present and past) on mantle stratification, fluid content and magmatism along the major convergent margins. We explore the regional variations of the 410 km and 660 km discontinuities by careful analyses of the underside reflected S-wave energy (SS precursors) from mantle interfaces using nonlinear, simultaneous inversions of shear velocity and discontinuity topography. We find that the 410 km and 660 km discontinuity depths are strongly anti-correlated if the dipping angles of the non-vertical structures were taken into account. Beneath the volcanic centers in Northeast China, our simultaneous solutions provide compelling evidence for the source of deep-rooted mantle melting in association with the dehydration process of the stagnant Pacific slab. An independent study using Singular Spectrum Analysis (SSA) for random noise removal and reconstruction of missing traces shows a significant enhancement of signals associated with mantle conversions beneath southwestern Canada. In addition to strong conversions from the transition zone phase boundaries, strong signals from the mid-transition zone reflectors can also be identified. Finally, our results from pre-stack depth migration of precursory arrivals reveal small-sale variations (< 500 km) on the discontinuity topography, due to the focusing of the diffracted energy to its true position. In Southeast Asia, the discontinuity depth measurements indicate maximum undulations of ~ 40 km on both transition zone discontinuities along the Sunda and Banda arcs. The correlation between the discontinuity depths and previously reported seismic velocities suggests that the upper mantle phase boundaries are thermally, rather than compositionally, controlled.
Language
English
DOI
doi:10.7939/R3CR5NR0G
Rights
This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for the purpose of private, scholarly or scientific research. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
Citation for previous publication
Dokht, R.M., Gu, Y.J. and Sacchi, M.D., 2016. Waveform inversion of SS precursors: An investigation of the northwestern Pacific subduction zones and intraplate volcanoes in China. Gondwana Research, 40, pp.77-90.Dokht, R.M., Gu, Y.J. and Sacchi, M.D., 2016. Singular Spectrum Analysis and its applications in mapping mantle seismic structure. Geophysical Journal International, p.ggw473.

File Details

Date Uploaded
Date Modified
2017-01-20T18:02:40.842+00:00
Audit Status
Audits have not yet been run on this file.
Characterization
File format: pdf (Portable Document Format)
Mime type: application/pdf
File size: 131254793
Last modified: 2017:06:13 12:20:53-06:00
Filename: MohammadHosseiniDokht_Ramin_201701_PhD.pdf
Original checksum: 1829def0d60589eb9353e5077d9ab2bd
Well formed: true
Valid: true
Page count: 166
Activity of users you follow
User Activity Date