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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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).",
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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).

AB - 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