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    Kansas refraction profiles

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    KSrefractionProfiles.pdf (1.623Mb)
    Issue Date
    1989
    Author
    Steeples, Don W.
    Miller, Richard D.
    Publisher
    Kansas Geological Survey
    Type
    Technical Report
    Is part of series
    Kansas Geological Survey Bulletin

    226
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    Abstract
    Historically, refraction surveys have been conducted in hopes of mapping distinct layers within the earth. Refraction is a useful tool provided its limitations and the assumption that layers increase in seismic velocity with increasing depth are kept in mind. A traditional reversed-refraction profile was conducted along a 500-km (300- mi)-long east-west line extending from Concordia, Kansas, to Agate, Colorado. Analysis of the data showed an average crustal velocity of 6.1 kmlsec (3.7 milsec) and an average upper-mantle P phase velocity of 8.29 kmlsec (4.97 milsec) with a Moho depth calculated to be 36 km (23 mi) on the eastern end and 46 km (29 mi) on the western end. Some evidence suggests velocities as high as 7.2 kmlsec (4.3 milsec) in the crust at various locations along the survey line. The strong east-west regional gravity gradient of -0.275 mgalb supports the seismically drawn conclusion of a thinning of crust in north-central Kansas. In order to supplement the data from this refraction survey, we took advantage of the Kansas earthquake seismograph network. A crustal study using earthquakes as energy sources and a regional earthquake network as seismometer locations resulted in a crustal-velocity model that will improve determination of local earthquake locations. A large anomalous body in the upper mantle/lower crust, assumed to be related to the Precambrian-aged Midcontinent Geophysical Anomaly (MGA), resulted in early Pwave arrivals from refracted energy from the Moho recorded at Concordia, Salina, Tuttle Creek, and Milford. An omnidirectional positive P residual zone near El Dorado may be related to the Wichita geomagnetic low. Some evidence suggests the presence of a lower velocity material on the western and eastern flanks of the MGA, possibly representing the Rice Formation. A P velocity of 8.25 krn/sec±0.1k m/sec (4.95 mi/sec+0.09m i/sec) with the crust thinning from west to east and an apparent thinning from the north and from the south was determined from the 16 regional earthquakes studied. Crustal thickness from central Kansas through western Missouri seems to be relatively consistent.
    URI
    http://hdl.handle.net/1808/1649
    Collections
    • Distinguished Professors Scholarly Works [918]
    • Geology Scholarly Works [245]
    Citation
    in Proc. of Symposium on Geophysics in Kansas, D. W. Steeples, ed.: Kansas Geol. Survey Bull. 226, 129–164.

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    785-864-8983
    KU Libraries
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    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
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    Contact KU ScholarWorks
    785-864-8983
    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    785-864-8983

    KU Libraries
    1425 Jayhawk Blvd
    Lawrence, KS 66045
    Image Credits
     

     

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