An investigation of upper mantle velocity structure below the northern Mississippi Embayment and the southern Illinois Basin using teleseismic earthquake tomography and inversion of Rayleigh wave phase velocities
Date of Award
Doctor of Philosophy
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.
Dissertation or thesis originally submitted to ProQuest
Geng, Yu, "An investigation of upper mantle velocity structure below the northern Mississippi Embayment and the southern Illinois Basin using teleseismic earthquake tomography and inversion of Rayleigh wave phase velocities" (2021). Electronic Theses and Dissertations. 2897.
Available for download on Wednesday, February 07, 2024