Electronic Theses and Dissertations

Date

2026

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Earth Sciences

Committee Chair

Chris Cramer

Committee Member

Charles Langston

Committee Member

Christodoulos Kyriakopoulos

Committee Member

David Arellano

Committee Member

Thomas Goebel

Abstract

This study presents a broadband magnetotelluric (MT) investigation of crustal resistivity structure beneath the New Madrid Seismic Zone (NMSZ), aimed at identifying conductive features that may control present-day intraplate seismicity. Because electrical resistivity is sensitive to fluid content, temperature, and rock fabric, it provides indirect constraints on crustal strength and deformation processes, which influence fault reactivation and earthquake occurrence. We collected MT data along a profile spanning the Axial and Reelfoot faults to image subsurface conductivity contrasts associated with these active fault zones. We conducted a broadband magnetotelluric (MT) survey from December 2021 to March 2023 across five profiles- spanning the Axial and Reelfoot faults of the New Madrid Seismic Zone. The purpose of this experiment was to discover possible fault structure reflected in resistivity anomalies. The data span a wide frequency range from 0.00005 to 10000 Hz. Four shallow profiles were collected near Steele and Caruthersville in the Missouri Bootheel. One deeper lithospheric profile runs from Obion, Tennessee to Wardell, Missouri, crossing the Reelfoot Rift and the Axial Fault and imaging down to around 80 kilometers. The results show that earthquake clusters are located within a zone of very high resistivity, in the range of 1000 to 10000 Ohm meter. These locations also match with low seismic velocity zones from earlier studies, supporting the interpretation that fault locking dominates in the brittle crust. At depths between 2 to 30 kilometers, most profiles show a conductive anomaly southeast of the fault. This may represent a weaker and more ductile zone that helps transfer stress into the stronger and locked brittle section of the fault. Further south, we investigated the resistivity structure across the Alabama Oklahoma Lineament (AOL), which marks a major tectonic boundary and also defines the southern edge of the Mississippi Embayment (ME). Our MT data reveal a steep conductive zone with values around 50 to 100 Ohm meter, separating resistive blocks around 500 to 1000 Ohm meter. This contrast matches sharp differences in regional heat flow and suggests that the AOL is a tectonic weak zone still influencing crustal deformation and regional seismicity. Under the Mississippi Embayment, the lithosphere shows normal resistivity values from 500 to 1000 Ohm-meters down to at least 100 to 150 kilometers. However, west of the embayment and north of the AOL, we observe an anomalously conductive region with resistivity as low as 10 Ohm meter beneath the Enola area in Arkansas. If this anomaly is due to the presence of fluids, it may explain the swarm type seismicity observed there. In summary, the results show that both fault locking, rheology and fluid presence control seismicity in the NMSZ and surrounding regions, but their influence depends on depth and location.

Comments

Data is provided by the student

Library Comment

Dissertation or thesis originally submitted to ProQuest/Clarivate.

Notes

Open Access

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