Electronic Theses and Dissertations

Yixin Zhang

Date

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Earth Sciences

Committee Chair

Christine Powell

Committee Member

Charles A Langston

Committee Member

Chris H Cramer

Committee Member

Randel T Cox

Committee Member

Stephen P Horton

Abstract

This dissertation is focused on the study of faulting kinematics in the New Madrid Seismic Zone (NMSZ). The dissertation contains two parts, and both use seismic data recorded by the Center for Earthquake Research and Information in the time span Jan 1st 2000 to Dec 31st 2019. In the first study, hypocenters were relocated using the hypoDD inversion method. The relocations were then used to model fault planes using Optimal Anisotropic Dynamic Clustering analysis. Twelve fault planes were modeled indicating that fault structure the NMSZ is more complex than indicated in previous studies. Three fault planes are modeled at the southwest end of the Axial fault around the Osceola Igneous Complex. As in previous studies, the Reelfoot fault is divided into northern and southern sections at the intersection of the Axial fault. The northern Reelfoot fault can be modelled as one fault plane. The southern Reelfoot fault is separated into two distinct sections at the crosscutting Ridgley fault. Four fault planes are modeled between the eastern end of the northern Reelfoot fault and the Ridgley fault. The second study involved determination of 166 focal mechanisms for earthquakes with magnitudes equal to and greater than 2.5 and an associated stress inversion. Reverse and strike slip faulting occur along all the major fault segments. Both types of faulting are equally prevalent on the Reelfoot fault, suggesting that this fault is cut by numerous northeast trending right-lateral strike-slip faults. Our analysis reveals that maximum horizontal stress directions differ on the major fault segments. Except for the West fault, the maximum horizontal stress directions are rotated clockwise by different amounts relative to the northeast-southwest contraction elsewhere in the central United States. The location of axial and rift margin intrusions may be influencing deformation style and stress orientation within the NMSZ. Our results suggest that the Axial fault passes through Reelfoot fault and that slip on the Axial fault may be transferred to both reverse and strike-slip motions on the Reelfoot fault.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Embargoed until 07-30-2026

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Available for download on Thursday, July 30, 2026

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