Electronic Theses and Dissertations

Identifier

6499

Author

Hee Choi

Date

2019

Date of Award

8-22-2019

Document Type

Thesis

Degree Name

Master of Science

Major

Earth Sciences

Concentration

Geophysics

Committee Chair

Eunseo Choi

Committee Member

Christine A Powell

Committee Member

Mitch Withers

Abstract

Evidence for asymmetric plate growth, variable crustal thickness, and non-uniform spreading rates is ubiquitous on the seafloor. However, conventional numerical modeling approaches are often incapable of explaining the non-uniform growth of oceanic lithosphere. Noting that plate-boundary forces can dynamically determine plate speed by finding a balance against the resistance to extension at ridge axes and at lithosphere-asthenosphere boundary, I introduce plate-boundary forces instead of kinematics to drive plate motions in numerical models for mid-ocean ridges. I construct such models using FLAC, an open-source finite element code for geodynamic simulations. My mid-ocean ridge models tested three different boundary conditions: Prescribed velocities, zero boundary force, and constant non-zero boundary force. All three types of boundary conditions can produce faulting styles consistent with the previous studies but mean plate speeds respond differently to different boundary condition types. Mean plate speed is almost constant in the kinematic and zero boundary force models. The constant non-zero force boundary conditions make plates move at 1.8 cm/yr of mean speed, but plate speed changes over time by more than 1 cm/yr. These model results suggest that even if far-field plate-driving forces are nearly constant, non-uniform seafloor growth can result. However, further investigation is necessary for reducing numerical noise and extracting mean plate speed with greater confidence.

Comments

Data is provided by the student.

Library Comment

dissertation or thesis originally submitted to the local University of Memphis Electronic Theses & dissertation (ETD) Repository.

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