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Enhancing Stratigraphic and Structural Features in GPR Images of Limestone Karst through Adequate Data ProcessingNormal access

Authors: W.E. Medeiros, J. Oliveira Jr., F. Santana, F. Bezerra and C. Cazarin
Event name: 24th European Meeting of Environmental and Engineering Geophysics
Session: Ground Penetrating Radar A
Publication date: 09 September 2018
DOI: 10.3997/2214-4609.201802479
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 1.76Mb )
Price: € 20

The demand for detailed understanding of karst formation process in carbonate rocks occasioned an accompanied demand for high quality GPR images. It is necessary to characterize from the images primary strata and to identify fractures, faults, and dissolution features, as an stage to establish spatial and genetic associations among these elements. However, materials infilling karst voids or resulting from carbonate rock weathering might be conductive and, as a result, penetration depth and signal resolution might be greatly reduced due to attenuation. Considerable effort must then be done to improve the image resolution in karst through data processing. We present a GPR processing flow highly tested in the limestone karst environment of the JandaĆ­ra Formation in Potiguar basin, Brazil, composed by the following main steps: static correction, dewow, background removal, spreading and exponential compensation gains, spectral balancing, Kirchhoff migration, band-pass filtering, topographic correction, and amplitude-volume enhancement. The spectral balancing step is of particular importance because, when judiciously applied, it can replace approximately the high frequency content lost by propagation effects. We also exemplify how image improvements obtained in 200 MHz datasets help the interpreter to better visualize the karst geometric elements, thus contributing to a deeper understanding of its formation process.

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