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Characterizing the geometry and time of deformation of the Meeman-Shelby Fault near Memphis, TN

Principal Investigator: M. Beatrice Magnani, University of Memphis

The goal of the experiment is to image the Paleozoic to Quaternary sedimentary deposits that fill the Mississippi Embayment in the Central U.S., south of the New Madrid Seismic Zone (NMSZ). The seismic acquisition will target the onshore continuation of the Meeman-Shelby Fault (MSF), recently imaged ~10 km north-west of Memphis, TN, along the Mississippi River (Central US) by a seismic marine reflection survey led by Dr. Magnani. The river data reveal that the 60 km-long fault has been active repeatedly since the Cretaceous. Folding of the Quaternary alluvium along the river shows that deformation is still ongoing, suggesting that the MSF might represent a greater threat to Memphis than the NMSZ itself. Due to the lack of resolution of the method and to the poor knowledge of the riverbed stratigraphy, Holocene activity and slip rates are difficult to detect along the profile. The proposed high-resolution reflection seismic acquisition will verify the location of the fault on land and help characterize the structure (style of faulting, variations in the third dimension). More importantly, identifying and imaging the fault on land will allow subsequent dating of key horizons through trenching, coring and geologic studies, providing the opportunity for bracketing the activity of the fault in time and to obtain age, amount of motions in the last events as well as recent slip rates. The project will open up several opportunities to investigate in detail the long-term behavior of this structure and contribute to the understanding of fault interactions in intraplate settings, and to earthquake hazard assessments in the Central US. This experiment promotes the basic goal of NEES "to engage and support earthquake risk-mitigation partners in experimental activities that improve the seismic design and performance of our infrastructure systems through the integration of people, ideas, and tools".

The proposed high-resolution seismic reflection profile will focus on the unconsolidated sediments of the Mississippi Embayment (Central US) from the Paleozoic sedimentary rocks to the Quaternary alluvium. The profile will cross the MSF at a high angle and will be long enough to account for bends and possible lateral variations in the fault geometry. Because the PI is interested in the recent tectonic history of the MSF, she plans to focus on the Cretaceous to Holocene section for the proposed survey, imaging with high resolution the Tertiary and Quaternary deposits. The PI is confident that the high impedance contrast of the Paleozoic/Cretaceous and Cretaceous/Tertiary interfaces will insure energy return from these depths.