The Geophysics Section of the Indiana Geological Survey has analyzed a continuous velocity log of the Indiana Farm Bureau No. 1 Luther Brown test well in Lawrence County, Ind. (SE¼SE¼ sec. 20, T. 5 N., R. 2 E), for interval and average vertical velocities from the New Albany Shale to the basement complex. Average vertical velocities from a datum within the New Albany Shale were 13,500 feet per second to the Knox Dolomite, 16,500 feet per second to the Mt. Simon Sandstone, and 16,250 feet per second to the basement complex. Data from the continuous velocity log were used to compute a synthetic seismogram. Comparison of this seismogram with a field seismogram made near the well shows good correlation of reflections from the Trenton Limestone, the upper and lower parts of the Knox Dolomite, the Eau Claire Formation, the Mt. Simon Sandstone, and a metasedimentary rock unit resting on basalt that is assigned to the basement complex. Although the continuous velocity log does not show a sharp velocity contrast at the top of the metasedimentary rock unit, the synthetic seismogram demonstrates that energy reflected from a series of small velocity contrasts combine to give a prominent reflection.



Biggs, M. E., Blakely, R. F., and Rudman, A. J., 1960, Seismic velocities and synthetic seismogram computed from a continuous velocity log of a test well to the basement complex in Lawrence County, Indiana: Indiana Geological Survey Report of Progress 21, 15 p., 4 figs.


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Keywords: geophysics, seismic

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