Exploration Geophysics Exploration Geophysics Society
Journal of the Australian Society of Exploration Geophysicists
RESEARCH ARTICLE

Microgravimetric and ground penetrating radar geophysical methods to map the shallow karstic cavities network in a coastal area (Marina Di Capilungo, Lecce, Italy)

Giovanni Leucci 1 3 Lara De Giorgi 2
+ Author Affliations
- Author Affliations

1 Institute for Archaeological and Monumental Heritage (CNR-IBAM), via per Monteroni, 73100 Lecce, Italy.

2 Department of Science of Materials, University of Salento, via per Monteroni, 73100 Lecce, Italy.

3 Corresponding author. Emails: g.leucci@ibam.cnr.it; gianni.leucci@unisalento.it

Exploration Geophysics 41(2) 178-188 https://doi.org/10.1071/EG09029
Submitted: 10 June 2009  Published: 7 June 2010

Abstract

The coastal area Marina di Capilungo located ~50 km south-west of Lecce (Italy) is one of the sites at greatest geological risk in the Salento peninsula. In the past few decades, Marina di Capilungo has been affected by a series of subsidence events, which have led in some cases to the partial collapse of buildings and road surfaces. These events had both social repercussions, causing alarm and emergency situations, and economic ones in terms of the funds for restoration.

With the aim of mapping the subsurface karstic features, and so to assess the dimensions of the phenomena in order to prevent and/or limit the ground subsidence events, integrated geophysical surveys were undertaken in an area of ~70 000 m2 at Marina di Capilungo. Large volume voids such as karstic cavities are excellent targets for microgravity surveys. The absent mass of the void creates a quantifiable disturbance in the earth’s gravitational field, with the magnitude of the disturbance directly proportional to the volume of the void. Smaller shallow voids can be detected using ground-penetrating radar (GPR). Microgravimetric and GPR geophysical methods were therefore used. An accurate interpretation was obtained using small station spacing and accurate geophysical data processing. The interpretation was facilitated by combining the modelling of the data with the geological and topographic information for explored caves. The GPR method can complement the microgravimetric technique in determining cavity depths and in verifying the presence of off-line features and numerous areas of small cavities, which may be difficult to be resolved with only microgravimetric data. However, the microgravimetric can complement GPR in delineating with accuracy the shallow cavities in a wide area where GPR measurements are difficult. Furthermore, microgravity surveys in an urban environment require effective and accurate consideration of the effects given by infrastructures, such as buildings, as well as those given by topography, near a gravity station. The acquired negative anomaly in the residual Bouguer anomalies field suggested the presence of possible void features. GPR and modelling data were used to estimate the depth and shape of the anomalous source.

Key words: ground-penetrating radar, Karstic features map, microgravimetric.


Acknowledgements

The authors are grateful to the reviewers and the Associate Editor for the precious suggestions that have improved this paper.


References

Beres, M., Luetscher, M., and Olivier, R., 2001, Integration of ground penetrating radar and microgravimetric methods to map shallow caves: Journal of Applied Geophysics 46, 249–262.
CrossRef |

Bergmann, T., Robertsson, J. O. A., and Holliger, K., 1998, Finite-difference modeling of electromagnetic wave propagation in dispersive and attenuating media: Geophysics 63, 856–867.
CrossRef |

Bishop I. , Styles P. , Emsley S. J. , and Ferguson N. S. , 1997, The detection of cavities using the microgravity technique: case histories from mining and karstic environments, in D. McCann, M. Eddleston, P. J. Femming, G. M. Reeves, eds., Modern geophysics in engineering geology. Special Publications, 12. Geological Society, pp. 155–168.

Blizkovsky, M., 1979, Processing and applications in microgravity surveys: Geophysical Prospecting 27, 848–861.
CrossRef |

Bruno, E., Calcaterra, D., and Parise, M., 2008, Development and morphometry of sinkholes in coastal plains of Apulia, southern Italy. Preliminary sinkhole susceptibility assessment: Engineering Geology 99, 198–209.
CrossRef |

Butler, D. K., 1984, Microgravimetric and gravity gradient techniques for detection of subsurface cavities: Geophysics 49, 1084–1096.
CrossRef |

Carcione, J. M., 1996, Ground-radar numerical modeling applied to engineering problems: European Journal of. Environmetal Engineering Geophysics 1, 65–81.


Cardarelli, E., Marrone, C., and Orlando, L., 2003, Evaluation of tunnel stability using integrated geophysical methods: Journal of Applied Geophysics 52, 93–102.
CrossRef |

Chamon, N., and Dobereiner, L., 1988, An example of the uses of geophysical methods for the investigation of a cavern in sandstones: Bulletin of the International Association of Engineering Geology 38, 37–43.
CrossRef |

Conyers L. B. , and Goodman D. , 1997, Ground-penetrating radar – an introduction for archaeologists: Alta Mira Press.

Daniels, J., 1988, Locating caves, tunnels and mines: Geophysics: The Leading Edge of Exploration 7, 32–52.
CrossRef |

Debeglia, N., and Dupont, F., 2002, Some critical factors for engineering and environmental microgravity investigations: Journal of Applied Geophysics 50, 435–454.
CrossRef |

Delle Rose, M., Federico, A., and Parise, M., 2004, Sinkhole genesis and evolution in Apulia, and their interrelations with the anthropogenic environment: Natural Hazards and Earth System Sciences 4, 747–755.
CrossRef |

Geotools Corporation, 2000, A division of AOA Geophysics Inc. 5828 Balcones Drive, Suite 204 Austin, Texas USA.

Goodman, D., 1994, Ground-penetrating radar simulation in engineering and archaeology: Geophysics 59, 224–232.
CrossRef |

Gottsche F. M. , 1997, Identification of cavities by extraction of characteristic parameters from ground probing radar reflection data: PhD Thesis, Christian-Albrechts University.

Grandjean, G., and Leparoux, D., 2004, The potential of seismic methods for detecting cavities and buried objects: experimentation at a test site: Journal of Applied Geophysics 56, 93–106.
CrossRef |

Johnson K. S. , 1987, Development of the Wink Sink in west Texas due to salt dissolution and collapse: Proceedings 2nd Multidisciplinary Conference on Sinkholes and the Environmental Impact of Karst, Orlando, pp. 127–136.

Leucci, G., 2003, Evaluation of karstic cave stability using integrated geophysical methods: GeoActa 2, 47–60.


Leucci, G., 2006a, Integrated geophysical, geological and geomorphological surveys to study the coastal erosion: International Journal of Soil Science 1, 146–167.
CrossRef |

Leucci, G., 2006b, Contribution of ground-penetrating radar and electrical resistivity tomography to identify the cavity and fractures under the main church in botrugno (Lecce, Italy): Journal of Archaeological Science 33, 1194–1204.
CrossRef |

Leucci, G., 2007a, Geophysical investigations to study the physical– mechanical characteristics of the rock in a coastal environment: the cliff of Roca (Lecce, Italy): Journal of Geophysics and Engineering 4, 462–475.
CrossRef |

Leucci, G., 2007b, Geoscientific investigations for mapping the subsidence risk in an urban area: Journal of Geophysics and Engineering 4, 317–331.
CrossRef |

Leucci, G., and De Giorgi, L., 2005, Integrated geophysical surveys to assess the structural conditions of a karstic cave of archaeological importance: Natural Hazards and Earth System Sciences 5, 17–22.
CrossRef |

Leucci, G., and De Giorgi, L., 2006, Experimental studies on the effects of fracture on the p and s wave velocity propagation in sedimentary rock (‘calcarenite del salento’): Engineering Geology 84, 130–142.
CrossRef |

Leucci, G., Negri, S., Carrozzo, M. T., and Nuzzo, L., 2002, Use of ground penetrating radar to map subsurface moisture variations in an urban area: Journal of Environmental & Engineering Geophysics 7, 69–77.
CrossRef |

Meier E. , Huggenberger P. , Stiefelhagen W. , Muller I. , and Christe R. , 1997, Geophysical methods as a tool for speleological and geotechnical investigation in karst Maira, Plateau de Bure JU, Switzerland: Proceedings of the 12th International Congress of Speleology, Switzerland, 2, 221–224.

Melchior P. , 1983, The tides of the planet earth: Pergamon.

Osborne, R. A. L., 2002, Cave breakdown by vadose weathering: International Journal of Speleology 31, 37–53.


Patterson, D. A., Davey, J. C., Cooper, A. H., and Ferris, J. K., 1995, The investigation of dissolution subsidence incorporating microgravity geophysics at Ripon, Yorkshire: Quarterly Journal of Engineering Geology 28, 83–94.
CrossRef |

Radhakrishna Murthy, I. V., and Swamy, K. V., 1996, Gravity anomalies of a vertical cylinder of polygonal cross-section and their inversion: Computers & Geosciences 22, 625–630.
CrossRef |

Rousset D. , Genthon P. , Perroud H. , and Senechal G. , 1998, Detection and characterization of near surface small karstic cavities using integrated geophysical surveys: Proceedings of the 4th Meeting of Environmental and Engineering Geophysical Society, European Section, Barcelona, Spain. pp. 367–370.

Sandmeier K. J. , 2008, Reflex 5.0 Manual. Sandmeier Software. Zipser Strabe 1, D-76227 (Karlsruhe, Germany).

Styles P. , 2004, Detection of caves by microgravity geophysics, in A. C. Waltham, F. G. Bell and M. G. Culshaw eds., Bahamas sinkholes and subsidence: Springer.

Styles, P., McGrath, R., Thomas, E., and Cassidy, N. J., 2005, The use of microgravimetry for cavity characterization in karstic terrains: Quarterly Journal of Engineering Geology and Hydrogeology 38, 155–169.
CrossRef |

Styles P. , Toon S. , Thomas E. , and Skittral M. , 2006, Microgravity as a tool for the detection, characterization and prediction of geohazard posed by abandoned mining cavities: First Break, vol 24.

Telford W. M. , Gedart L. P. , and Sheriff R. E. , 1990, Applied geophysics, 2nd edn: Cambridge University Press.

Tharp, T. M., 1999, Mechanics of upward propagation of cover-collapse sinkholes: Engineering Geology 52, 23–33.
CrossRef |

Van schoor, M., 2002, Detection of sinkholes using 2D electrical resistivity imaging: Journal of Applied Geophysics 50, 393–399.
CrossRef |

Yilmaz O. 1987. Seismic data processing: Society of Exploration Geophysicists.

Yule, D. E., Sharp, M. K., and Butler, D. K., 1998, Microgravity investigations of foundation conditions: Geophysics 63, 95–103.
CrossRef |



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