Semester of Graduation

Spring

Degree

Master of Science (MS)

Department

Geology and Geophysics

Document Type

Thesis

Abstract

I aim to constrain the crustal thickness of the Sabine Block in the Sabine Uplift region of northwest Louisiana, using the frequency domain receiver function deconvolution technique followed by H-κ stacking. The passive margin on the southern edge of the North American continent experienced an active tectonic history, including the spreading events that led to the formation of the Gulf of Mexico. A previous study proposed the Sabine Block is a residual fragment of Proterozoic orogenic origin; however, its full extent and geometry are up for debate. It is now overlain by thick sedimentary sequences ranging from ~4-6 km deposited over transitional crust that thins toward the southeast to ~30 km across ~400 km, possibly associated with the opening of the Gulf of Mexico. Gravity signatures related to this block are observed as high gravity anomalies in northwest Louisiana. The broad impacts of this study can refine regional tectonic reconstruction models and crustal thickness models.

Nine temporary broadband seismic stations from the Z7 broadband seismometer network were used in the initial analysis. These stations were recorded from June 2019 to August 2022. One hundred sixteen earthquakes were selected out of 295 events for receiver function computation. A crustal thickness analysis is done employing the H-κ stacking algorithm. Four stations (LA03, LA04, LA05, LA10) were eliminated from crustal thickness analysis due to the complicated Moho Ps phase. Furthermore, crustal velocity heterogeneities introduce uncertainty in crustal estimates, which are less than 2 km across all stations based on our method. LA01 provided the clearest Moho Ps arrivals and gives a crustal thickness of ~39 km. The average crustal thickness of the five stations is 38.4 km. Vp/Vs results vary from 1.76 to 1.89, with an average value of 1.82. Though the limitations of station coverage cannot discern the full extent of any crustal features, a trend of decreasing thickness towards the east based on stations LA07 and LA06 is observed in the study area.

Date

4-5-2024

Committee Chair

Patricia Persaud

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