POTENTIAL FIELD GEOPHYSICAL ANALYSIS OF THE MID-CONTINENT RIFT IN SOUTHEASTERN NEBRASKA

The Mid-Continent Rift System (MRCS) is an ancient 2000 km-long failed rift system that spans bilaterally from Oklahoma up to Michigan and down through Ohio in a horseshoe-like shape. It is commonly accepted to have formed as a result of massive tectonic extension approximately 1.11 Ga, only to be halted into a failed rift by the compressional stress exerted by the Grenville Orogeny 1.05 Ga. In Nebraska, the rift cuts through a small section of the southeastern corner of the state, travelling largely northeast between Lincoln and Omaha. There is a substantial gap in the MRCS spanning from Lincoln south to the Kansas border where no geophysical data has been mapped. The MCRS has been linked to numerous seismic events in Nebraska over the past fifty years, several of which are clustered around normal and strike-slip fault lines. Major clusters have occurred around the Nebraska-Kansas border and along the Nemaha fault. This study will aim to examine and model the subsurface structure of the MCRS within southeastern Nebraska, the location of numerous earthquake epicenters. Potential field measuring and seismic reflection and refraction will serve as the primary methods for imaging and gathering data on the subsurface structure of the MCRS. By interpreting and analyzing these geophysical data, a model of the MCRS’s structure and fault systems can be created, which will provide information regarding stress regimes and seismic impacts. Ultimately, we predict that there will be a causal link between the seismic activity and the MCRS, although the extent remains to be determined.