Date of Completion

5-3-2018

Embargo Period

5-3-2018

Keywords

tomography; random media; coherence functions; seismic imaging

Major Advisor

Vernon Cormier

Associate Advisor

Lanbo Liu

Associate Advisor

Richard Jones

Field of Study

Physics

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

This thesis presents a thorough study of the stochastic tomography technique, from theory to numerical validation and application in characterizing small-scale heterogeneity in Earth’s mantle using statistical approach. Fluctuations in amplitude and travel time of teleseismic P waves, measured by amplitude and phase coherences beneath elements of EarthScope seismic array, are used to invert for the heterogeneity spectrum of P velocity in a 1000 km thick region of the upper mantle beneath the array. Best fits to joint transverse coherence functions require a depth-dependent heterogeneity spectrum, with peaks in narrow depth ranges that agree well with the predictions for a temperature derivative of velocity that includes the effects of chemical and phase variations expected for standard models of the silicate mineral assemblage of the upper mantle. The results confirm the existence of significant chemical as well as thermal contributions to observed upper mantle heterogeneity at spatial scales between 50 km to 300 km.

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