Towards Construction of the Central United States Seismic Observatory and Calibration Site: Defining the Geologic Site Model-Part 2

Grants and Contracts Details


The University ofKentucky has drilled, logged, and instrumented a borehole that penetrated the 586-mthick Mississippi embayment soil/sediment deposits and terminated 8 meters into Paleozoic bedrock near the most active segment ofthe New Madrid seismic zone. As part ofthe installation ofthe new central United States seismic observatory borehole, an FY08-NEHRP study characterized the Tertiary to Paleozoic-aged subsurface geologic materials and configuration in the immediate vicinity (e.g., I-km radius) ofthe observatory site in order to provide future researchers with an accurate geologic model in which to effectively evaluate the 3-D soil/sediment transfer function; however, the "optimal CMF recording window" required for imaging these deeper stratigraphic FY08-NEHRP datasets precluded our resolving the near-surface Quaternary section. Consequently, the primarv objectives for the proposed study are to acquire additional CMF surveys coincident with the prior survey locations. but with a reconfigured array aperture optimally calibrated to resolve the Quaternary-aged impedance boundaries and their geometric configuration. The results (e.g. seismic fence diagrams. isopach maps, etc.) from the proposed study will be integrated with the FY08-NEHRP dataset to complete the geologic model at the CUSSO site for future 3D ground motion modeling. As a secondary objective we are interested in better estimating the near-surface extent ofa Significant fault imaged in the initial profiles. A three-dimensional ground-motion modeling and observational comparison cannot be accurately performed without knowledge ofthe subsurface configuration. Furthermore, smaller scale geologic anomalies can affect the spatial coherence ofthe observed ground motions between instruments, again degrading the accuracy ofthe modeled and observational comparison. Subsequent to understanding the transfer function at the new observatory, data collected from regional free-field instrumentation can be calibrated and extrapolated to understand the spatial variance of site effects throughout the central U.S. The completed observatory and calibration site will provide a unique field laboratory for seismic hazard assessment in the central United States, and the nation as a whole. An accurate site characterization is essential for maximum effectiveness, however.
Effective start/end date6/1/1112/31/12


  • US Geological Survey: $67,672.00


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