Back
Full-text
Journal article

Geoelectric mapping of near‐surface karstic fractures by using null arrays

  • Szalai, Sándor Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, POB 5, H‐9401 Sopron, Hungary. Emails:
  • Szarka, László Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, POB 5, H‐9401 Sopron, Hungary. Emails:
  • Prácser, Erno˝ Eötvös Loránd Geophysical Institute, Kolumbusz u. 17‐23, H‐1145 Budapest, Hungary.
  • Bosch, Frank University of Neuchâtel, Centre d'Hydrogéologie, 11, rue Emile Argand, CH‐2007 Neuchâtel, Switzerland.
  • Müller, Imre Geodetic and Geophysical Research Institute of the Hungarian Academy of Sciences, POB 5, H‐9401 Sopron, Hungary. Emails:
  • Turberg, Pascal Swiss Federal Institute of Technology Lausanne, Department of Civil Engineering, Laboratory of Geology, Ecublens, CH‐1015 Lausanne, Switzerland.
Show more…
Published in:
  • GEOPHYSICS. - Society of Exploration Geophysicists. - 2002, vol. 67, no. 6, p. 1769-1778
Geochemistry and Petrology
Geophysics
English The term “null array” is introduced for those electrode configurations where the measured potential difference is zero above a homogeneous half‐space when using a measuring dipole M0N0. Different types of null arrays (three‐electrode, Schlumberger, and dipole axial/equatorial null arrays) and their corresponding traditional arrays are studied. It was shown in a field study carried out in a karstified limestone area covered by thin sediments that it is possible to obtain geologically meaningful results with null‐array techniques. The main features of the null‐array data are as follows. (1) Null‐array data appear to be more spatially variable than the classical data. The spatial variability provides information about the presence of karstic fractures in the subsurface; (2) The null‐array anomalies caused by nearly vertical karstic fractures in the limestone basement do not decay with depth as quickly as the classical array anomalies. (3) The strike direction of the fractures is much less ambiguous than that found by using classical arrays. Nevertheless, the depth variation of the basement is more reliably observed in geoelectric anomalies obtained using traditional arrays. Therefore a joint use of classical arrays and their corresponding null methods is recommended, because the combined methods provide more information about the subsurface structure.
Language
  • English
Open access status
green
Identifiers
Persistent URL
https://sonar.ch/global/documents/166614
Statistics
Document views: 16 File downloads:
  • Full-text: 0