Electronic Theses and Dissertations

Yu Geng

Date

2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Earth Sciences

Committee Chair

Christine Powell

Committee Member

Christine Powell

Committee Member

Mitch Withers

Committee Member

Chris Cramer

Abstract

This dissertation presents three-dimensional seismic velocity models for the crust and upper mantle underneath the northern Mississippi Embayment and the southern Illinois Basin from joint local and teleseismic tomography (Vp and Vs) and by inverting Rayleigh wave phase velocities (Vs). Our study utilizes data observed by the Northern Embayment Lithospheric Experiment stations, the Center for Earthquake Research and Information New Madrid Seismic Network, the Earthscope Transportable Array, and the Ozark Illinois INdiana Kentucky Flexible Array. In both studies, we observed a low-velocity zone (LVZ) topped with fast velocities below the Reelfoot Rift; the high-velocity anomalies are attributed to depleted lowermost lithosphere and to mafic rocks emplaced beneath the Mississippi Embayment, similar to the situation in the North China Craton. In the teleseismic tomography study, we observed two anomalously slow regions at 240 km and 370 km depths, forming a northwest dipping LVZ that extends to the Illinois Basin. These two anomalies are interpreted as due to metasomatism of mantle rocks by hydrous, silica-rich fluids ascending from a slab fragment. We suggest that the LVZs below the Mississippi Embayment and the Illinois Basin are linked to the presence of a large igneous province. LVZs are imaged below the New Madrid seismic zone, the Wabash Valley seismic zone, and the Ste. Genevieve seismic zone, suggesting a connection between seismic velocities in the mantle and the occurrence of intraplate earthquakes.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest

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