Manuel Senos Matias

The use of gravity methods in the internal characterization of landfills - a case study.

Some examples of the use of gravity exploration methods in landfills were published recently. However, density contrast between the landfill and the host media as well as the cost involved may be limiting factors to the application of gravimetry to this problem. Herein a case study of the application of gravity methods to the internal characterization of a sealed landfill is presented. This landfill is installed in recent low-density quaternary sand formations. Two north–south gravity profiles were carried out. The first profile crossed the landfill at its centre, whilst a second profile was done some distance away from the landfill to provide general regional information. The first profile was modelled in order to obtain lateral variations of density within the landfill that might be caused by different types of waste and/or the age of the waste deposits. Gravity modelling and interpretation were supported with data from resistivity profiles carried out in the immediate vicinity of the gravity measurements, i.e. the resistivity profiles interpretation results constrained the thickness of landfill deposits.

A multi-method high-resolution geophysical survey in the Machado de Castro museum, central Portugal

Restoration of historical buildings is a delicate operation as they are often built over more ancient and important structures. The Machado de Castro Museum, Coimbra, Central Portugal, has suffered several interventions in historical times and lies over the ancient Roman forum of Coimbra. This building went through a restoration project. These works were preceded by an extensive geophysical survey that aimed at investigating subsurface stratigraphy, including archeological remains, and the internal structure of the actual walls. Owing to the needs of the project, geophysical data interpretation required not only integration but also high resolution. The study consisted of data acquisition over perpendicular planes and different levels that required detailed survey planning and integration of data from different locations that complement images of the surveyed area. Therefore a multi-method, resistivity imaging and a 3D ground probing radar (GPR), high-resolution geophysical survey was done inside the museum. Herein, radargrams are compared with the revealed stratigraphy so that signatures are interpreted, characterized and assigned to archeological structures. Although resistivity and GPR have different resolution capabilities, their data are overlapped and compared, bearing in mind the specific characteristics of this survey. It was also possible to unravel the inner structure of the actual walls, to establish connections between walls, foundations and to find older remains with the combined use and spatial integration of the GPR and resistivity imaging data.

A EM geophysical survey over an abandoned coal mining area S Pedro da Cova (North Portugal)

The environmental recovery of former mining areas and communities is an economical activity of increasing importance. Among other aspects such activity must include careful planing and an accurate knowledge of the positioning of old mining works. Frequently these works were conducted underground; very often the location of these works is very difficult because of their complexity as well as lack of information. Thus Geophysics can be very helpful both in their location and in the study of their influence on subsurface geological formations.

A study of the orientational variation of induced polarization time domain data

The Induced Polarization Exploration Method has been used intensively in areas of complex geology. In such areas pronounced orientational effects have been observed in resistivity measurements. However the orientational behaviour of induced polarization data has been overlooked.

A combined square array resistivity and magnetic survey in the archaelogical site of Noville, Coruna, Spain

Geophysical exploration techniques have been adapted to archaeological exploration successfully. The use of Exploration Geophysics in Archeology has proved to be a fast and economical tooI in excavation planning of archaeological sites.