A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Abstract

    A shallow seismic refraction survey and DC Resistivity Soundings were undertaken at southeastern margin of the Palaeo Ngami Lake to determine the structure and shallow stratigraphy of the lake; determine the amount of fault displacement at the border fault of the lake. The results of the seismic refraction survey indicate that the there is a low velocity zone (~500m/s) in the area which is thinner outside the lake (less than 10m) and much thicker toward the centre of the lake (more than 30m).This low velocity zone is underlain by a higher velocity (3125 m/s) layer. Augering results within the lake indicate that the low velocity zone consists of dry clays, diatomaceous earth/silts. The high velocity layer is believed to be made up of sandstone/siltstones. Fault displacement at the margin of the lake is about 21m of downthrow. Another downthrow (about 19m) occurs at a distance of about 1300m from the margin into the lake, thus resulting in a total throw of about 50m. The results of the DC resistivity sounding indicates that the low velocity zone within the lake is characterized by 3 distinct layers; the top layer which is less than 1 m thick, has a resistivity of about 1300 Ωm (dry hard clays), the second layer about 5 m thick and has a resistivity of 34 Ωm (diatomaceous earth) and the third layer has a resistivity of about 11 Ωm (whitish soft clays interlayered with silty units).

    Original languageEnglish
    Title of host publicationEnvironmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation
    Pages498-506
    Number of pages9
    Volume1
    Publication statusPublished - 2007
    Event20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007 - Denver, CO, United States
    Duration: Apr 1 2007Apr 5 2007

    Other

    Other20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007
    CountryUnited States
    CityDenver, CO
    Period4/1/074/5/07

    Fingerprint

    Botswana
    structural control
    seismic refraction
    Refraction
    lakes
    Lakes
    refraction
    electrical resistivity
    margins
    direct current
    lake
    low velocity zone
    low speed
    clays
    Clay
    fault displacement
    diatomite
    sounding
    Earth (planet)
    clay

    All Science Journal Classification (ASJC) codes

    • Geophysics
    • Geotechnical Engineering and Engineering Geology
    • Environmental Engineering

    Cite this

    Shemang, E. M., Molwalefhe, L. N., & Mosweu, E. (2007). A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity. In Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation (Vol. 1, pp. 498-506)
    Shemang, Elisha M. ; Molwalefhe, Loago N. ; Mosweu, Elvis. / A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity. Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1 2007. pp. 498-506
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    title = "A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity",
    abstract = "A shallow seismic refraction survey and DC Resistivity Soundings were undertaken at southeastern margin of the Palaeo Ngami Lake to determine the structure and shallow stratigraphy of the lake; determine the amount of fault displacement at the border fault of the lake. The results of the seismic refraction survey indicate that the there is a low velocity zone (~500m/s) in the area which is thinner outside the lake (less than 10m) and much thicker toward the centre of the lake (more than 30m).This low velocity zone is underlain by a higher velocity (3125 m/s) layer. Augering results within the lake indicate that the low velocity zone consists of dry clays, diatomaceous earth/silts. The high velocity layer is believed to be made up of sandstone/siltstones. Fault displacement at the margin of the lake is about 21m of downthrow. Another downthrow (about 19m) occurs at a distance of about 1300m from the margin into the lake, thus resulting in a total throw of about 50m. The results of the DC resistivity sounding indicates that the low velocity zone within the lake is characterized by 3 distinct layers; the top layer which is less than 1 m thick, has a resistivity of about 1300 Ωm (dry hard clays), the second layer about 5 m thick and has a resistivity of 34 Ωm (diatomaceous earth) and the third layer has a resistivity of about 11 Ωm (whitish soft clays interlayered with silty units).",
    author = "Shemang, {Elisha M.} and Molwalefhe, {Loago N.} and Elvis Mosweu",
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    Shemang, EM, Molwalefhe, LN & Mosweu, E 2007, A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity. in Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. vol. 1, pp. 498-506, 20th Symposium on the Application of Geophysics to Engineering and Environmental Problems: Geophysical Investigation and Problem Solving for the Next Generation, SAGEEP 2007, Denver, CO, United States, 4/1/07.

    A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity. / Shemang, Elisha M.; Molwalefhe, Loago N.; Mosweu, Elvis.

    Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1 2007. p. 498-506.

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

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    N2 - A shallow seismic refraction survey and DC Resistivity Soundings were undertaken at southeastern margin of the Palaeo Ngami Lake to determine the structure and shallow stratigraphy of the lake; determine the amount of fault displacement at the border fault of the lake. The results of the seismic refraction survey indicate that the there is a low velocity zone (~500m/s) in the area which is thinner outside the lake (less than 10m) and much thicker toward the centre of the lake (more than 30m).This low velocity zone is underlain by a higher velocity (3125 m/s) layer. Augering results within the lake indicate that the low velocity zone consists of dry clays, diatomaceous earth/silts. The high velocity layer is believed to be made up of sandstone/siltstones. Fault displacement at the margin of the lake is about 21m of downthrow. Another downthrow (about 19m) occurs at a distance of about 1300m from the margin into the lake, thus resulting in a total throw of about 50m. The results of the DC resistivity sounding indicates that the low velocity zone within the lake is characterized by 3 distinct layers; the top layer which is less than 1 m thick, has a resistivity of about 1300 Ωm (dry hard clays), the second layer about 5 m thick and has a resistivity of 34 Ωm (diatomaceous earth) and the third layer has a resistivity of about 11 Ωm (whitish soft clays interlayered with silty units).

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    Shemang EM, Molwalefhe LN, Mosweu E. A geophysical investigation of the structural controls along the southern margin of Lake Ngami, northwestern Botswana using seismic refraction and DC resistivity. In Environmental and Engineering Geophysical Society - 20th, SAGEEP 2007: Geophysical Investigation and Problem Solving for the Next Generation. Vol. 1. 2007. p. 498-506