**ERT and the Location of Mining Cavities in Anisotropic Media: A Field Example**

Manuel Matias and Fernando Almeida

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.68475

#### **Abstract**

[45] Kutra S, Rudzianskaite A. Organic matter concentration in water of the karst zone dug wells. Proceedings of The Fourth International Scientific Conference Rural Development'

[46] Rutkovienė V, Kusta A, Kutra S, Česonienė L. Šachtinių šulinių vandens taršos sezoninė

[47] Arustienė J, Kriukaitė J. Climate cange impact on groundwater resources. In: Kadūnas K, editor. Lietuvos Požeminio Vandens Monotoringas 2005‐2010 m. ir kiti hidrogeolog‐ iniai darbai. Vilnius: Lietuvos Geologijos Tarnyba; 2011. pp. 84‐89 (In Lithuanian) [48] Giedraitienė J. Change of groundwater level regime associated with meteorological con‐ dition). In: Kadūnas K, editor. Lietuvos požeminio vandens monotoringas 2005‐2010 m. ir kiti hidrogeologiniai darbai. Lithuania: Lietuvos Geologijos Tarnyba, Vilnius; 2011.

[49] Dėl Šiaurės Lietuvos karstinio rajono ribų ir intensyvaus karsto žemių grupių nustatymo [Internet]. 2008. Available from: https://www.e‐tar.lt/portal/lt/legalAct/TAR.59906C3193F6

2009; 15‐17 October 2009. Akademija; 2009. pp. 34‐37

kaita. Vandens Ūkio Inžinerija. 2003;**22**:15‐29

pp. 13‐22 (In Lithuanian)

116 Cave Investigation

[Accessed: 8‐12‐2016]

Often cave location requires the use of surface indirect techniques, such as geophysical methods. In particular, electrical methods have been applied to cavity exploration with evident success. However, as any other indirect methods, the use of these techniques has advantages and disadvantages. Cavities may be too small, too deep or masked by local geology to be detected. Nevertheless, indirect methods provide non-invasive, low cost and fast techniques to carry out the reconnaissance of an area where the presence of cavities is suspected. Complex geological conditions and formations anisotropy can induce strong orientational variation on ground resistivity measurements and, therefore, mask the presence of caves. Herein a field study in an old mining area demonstrates that 2D resistivity data—electrical resistivity tomography (ERT)—can be strongly affected by local anisotropy that masks the presence of cavities in ERT data modelling. In these cases, specific field strategies must be considered to overcome misleading interpretations and modelling, so that, meaningful results are obtained, uncertainty and interpretation ambiguity are reduced and the correct diagnosis of caves is accomplished.

**Keywords:** exploration, cavity, orientation, ERT, anisotropy
