Doctoral Dissertations

Youqiang Yu

Keywords and Phrases

Okavango Rift Zone; Mantle transition zone; Receiver functions; Reverberation-removal technique; Sedimentary and crustal thickness; Upper mantle anisotropy

Abstract

The mechanisms of rifting have been intensively investigated using geological and geophysical techniques beneath mature rift zones. However, current understanding on the earliest stages of rifting is seriously limited. Here we employ recently archived data from 17 broadband seismic stations traversing northern Botswana to conduct the first shear wave splitting and mantle transition zone (MTZ) studies within the Okavango Rift Zone (ORZ). The ORZ is an incipient continental rift situated at the terminal of the southwestern branch of the East African Rift System. The resulting normal MTZ thickness and consistently rift-parallel fast polarizations imply an absence of significant thermal anomalies in the upper mantle, ruling out the role of mantle plumes in the initiation of the ORZ. The observed anisotropy beneath the ORZ and adjacent areas is mainly attributed to the relative movement between the lithosphere and asthenosphere with regional contributions from fabrics in the lithosphere and flow deflection by the bottom of the lithosphere. Our observations imply that the initiation and development of the ORZ can be initiated following a passive mode from the consequences of relative movements between the South African block and the rest of the African plate along a zone of lithospheric weakness between the Congo and Kalahari cratons.

In addition, an approach was developed to effectively remove the near surface reverberations in the resulting receiver functions, decipher the P-to-S converted phases associated with the Moho discontinuity, and thus resolve sub-sediment crustal structure beneath stations sitting on a low-velocity sedimentary layer."--Abstract, page iii.

Advisor(s)

Gao, Stephen S.
Liu, Kelly H.

Committee Member(s)

Eckert, Andreas
Rogers, J. David
Mickus, Kevin

Department(s)

Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Geology and Geophysics

Sponsor(s)

National Science Foundation (U.S.)
China Scholarship Council

Publisher

Missouri University of Science and Technology

Publication Date

Summer 2015

Journal article titles appearing in thesis/dissertation

  • No thermal anomalies in the mantle transition zone beneath an incipient continental rift: Evidence from the first receiver function study across the Okavango Rift, Botswana
  • Seismic anisotropy beneath the incipient Okavango Rift: Implications for rifting initiation
  • Determining crustal structure beneath seismic stations overlying a low-velocity sedimentary layer using receiver functions

Pagination

xii, 87 pages

Note about bibliography

Includes bibliographic references.

Geographic Coverage

Okavango Rift Zone, Botswana

Rights

© 2015 Youqiang Yu, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Subject Headings

Rifts (Geology) -- Botswana
Seismic waves -- Mathematical models
Shear waves -- Measurement
Earth (Planet) -- Mantle
Anisotropy

Thesis Number

T 10773

Electronic OCLC #

921179059

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Dissertation Location

 
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