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Modelling azimuthal resistivity sounding over a laterally changing resistivity subsurface
Author(s) -
Watson Kathryn A.,
Barker Ron D.
Publication year - 2005
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2004024
Subject(s) - anisotropy , geology , electrical resistivity and conductivity , azimuth , depth sounding , economic geology , gemology , offset (computer science) , igneous petrology , geophysics , vertical electrical sounding , regional geology , mineralogy , engineering geology , hydrogeology , geotechnical engineering , geometry , seismology , metamorphic petrology , optics , volcanism , aquifer , groundwater , physics , mathematics , computer science , tectonics , programming language , oceanography , quantum mechanics
Rotational or azimuthal resistivity sounding is frequently employed for determining the electrical anisotropy of the subsurface. From this, the orientation of fracturing which might give rise to the anisotropy is interpreted. However, 4‐electrode arrays, such as the Wenner or Schlumberger, are strongly ambiguous and will produce an anisotropy‐style signature also over dipping strata or a gra‐dational lateral change in rock resistivity. However, this problem may be overcome by use of a 5‐electrode offset Wenner array. Simple computer modelling of rotational soundings is sufficient to demonstrate that azimuthal Wenner surveys, conducted on ground where there is a lateral variation in resistivity, will produce results similar to those recorded on truly anisotropic ground, whereas alternative techniques, such as offset Wenner azimuthal sounding, will successfully differentiate the two models.