Thesis Defense Announcement

College of Arts and Sciences announces the Final Thesis Defense of

Hee Choi

for the Degree of Master of Science

May 17, 2019 at 09:00 AM  CERI Seminar Room, 3892 Central Ave.

Advisor: Eunseo Choi

New Numerical Mid-Ocean Ridge Models for Interactions between plate-driving and resistant forces

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 be resulted. However, further investigation is necessary for reducing numerical noise and extracting mean plate speed with greater confidence.