Reduction of the archaeological risk by means of geophysical methods. An example from the south-west of peloponnese (Greece)

The “a priori” knowledge of the physical and characteristics and the geometry of the subsoil is the basic element both for the optimisation of the design of engineering constructions, and the means to avoid or reduce the so called “archaeological risk” which can cause the interruption of engineering works. On the other hand the imperfect knowledge of the subsoil characteristics and the thoughtless or forbidden intervention that can follow, can produce the loss of the cultural goods without the “memory” of the archaeological remains. Practically that is very usual in the “urgency” condition and especially in urban areas and/or in a building construction. In such cases it is very hard to preserve the archaeological structures. It is well known that the subsoil knowledge can be obtained by the application of appropriate geophysical methods. They must be applied with care taking into account the context, the dimensions of the archaeological bodies, the presence of noise sources, the physical properties of the materials. The choice must also be made taking into account the economic aspect: the geophysical methods must be “convenient” in respect to the economic value of quality and cheaper than other methods like archaeological diggings or excavations. Normally in archaeological research it is necessary to acquire substantial data, which must be filtered, processed and interpreted in order to give a detailed reconstruction of the subsoil. All data must be ordered and normalized to give a pseudo 3D reconstruction: The quantity of data can make the direct excavation process long and expansive. Archaeological Heritage has different dimensions and characteristics, so the choice of geophysical methods depends on the type of archaeological structure that it needs to show. Type of measure, sampling rate, profiling distance, have to be compared to archaeological structure. To establish the convenience of Geophysics an economic parameter (Marchisio and Ranieri, 2000) can be applied: Monetary Expected Value of the archaeological heritage is the product of the probability to discover the object and its monetary value. Besides it’s possible to define the intrinsic value of geophysical information and value the quantity of methods to apply.