HIGH RESOLUTION LOCAL EARTHQUAKE TOMOGRAPHY ACROSS THE NEMAHA UPLIFT, NORTH-CENTRAL OKLAHOMA, USA
Stevens, Nathan Thomas
Recent earthquakes in north central Oklahoma are primarily hosted on unmapped faults in the crystalline basement but are sparse in the largest regional structure, the Nemaha uplift. This absence is despite the presence of numerous high-rate salt water disposal wells near large faults of the uplift. This thesis presents compressional (Vp) and shear (Vs) tomographic velocity models across the uplift using a new catalog of 25,601 local earthquakes recorded by 131 local seismic stations operating between 2013 and 2017. Seismic velocities are consistent with expected basement geology outside the uplift; Vp and Vs values are diminished by upwards of 2.5% within the uplift. The decrease in seismic velocity is interpreted to represent increased fault density and increased fluid volume within the uplift, with an associated increase in basement permeability. An increase in permeability may inhibit the buildup of fluid pressure within the uplift, possibly contributing to local aseismicity.
induced seismicity; Oklahoma; Double Difference Tomography; Local Earthquake Tomography; Shallow Crustal Structure; Geophysics; Geology
Keranen, Kathleen Mary
Lohman, Rowena B.
M.S., Geological Sciences
Master of Science
dissertation or thesis