Bound Volume Number

2

Document Type

Honors Capstone Project

Date of Submission

Spring 5-1-2015

Capstone Advisor

Dr. Robert Moucha

Honors Reader

Dr. Gregory Hoke

Capstone Major

Earth Sciences

Capstone College

Arts and Science

Audio/Visual Component

no

Keywords

outer rise, lithospheric plate, numerical modeling, tensile deformation, Japan, South America

Capstone Prize Winner

no

Won Capstone Funding

no

Honors Categories

Sciences and Engineering

Subject Categories

Geology | Geophysics and Seismology | Tectonics and Structure

Abstract

The outer rise is a subtle ridge on the seafloor located near an oceanic trench where a down-going lithospheric plate begins to bend and thus fault prior to subducting at the subduction zone. During subduction, the descending lithospheric plate bends upwards, leading to normal faulting. This normal faulting, or deformation pattern, is hypothesized to be controlled by the subducting plate’s age, rheology, subduction velocity and angle. The two main goals of this study were to: 1) numerically model the influence of plate age, subduction angle, plate speed, and rheological parameters on outer-rise tensile deformation, and 2) characterize the regions of tensile deformation and compare these to the subducting plates in northeastern Japan and South America. I observed significant differences in the lateral extent and modest variations in the vertical extent of the outer-rise deformation region that I primarily attribute to differences in the imposed subduction angle representative of the two geographical locations. With a steeper subduction angle, the material has a more compact area to deform in, thus creating a deeper “wedge” of deformation. The rheological properties, however, play a more significant role in the lateral spread of the deformation. As a model’s internal friction angle increases, its ability to deform decreases, resulting in a narrower section of deformation. Also, the cohesion of the models lead to the observation that a more cohesive, or unified material, had more difficulty deforming than those that were less cohesive. Models that were run with lesser values of cohesion had a greater lateral spread of the deformation region as opposed to those with higher values of cohesion.

Creative Commons License

Creative Commons Attribution 3.0 License
This work is licensed under a Creative Commons Attribution 3.0 License.

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