Geophysical Observations at Archaeological Sites: Estimating Informational Content

Abstract

The application of geophysical methods to archaeological sites is limited by physical, environmental, economic and time considerations. The presence of numerous kinds of noise means that in many cases the archaeological targets and surrounding media are best approached as probabilistic objects, such that the amount of information potentially available from different geophysical methods can be estimated by probabilistic and statistical methods, including the risks associated with this decision-making. Here it is shown that simple informational and probabilistic criteria can be applied to formalize the information that can be obtained by applying different geophysical methods. To assess their relative value, geophysical methods, geophysical information and cost and time factors are convoluted in order to generate integrated parameters. This theoretical presentation of the information parameters is illustrated by the calculation of actual results. The solution to this 'four colour' mathematical problem shows that two independent geophysical methods are sufficient to characterize the archaeological potential of a site. M, magnetization; R, resistivity; J 1 and J 2 are the magnetization of target and surrounding rocks, respectively; ρ 1 and ρ 2 are the resistivity of target and surrounding rocks, respectively 128 L. V. Eppelbaum Figure 3. Maps of (A) magnetic and (B) self-potential (SP) fields at the Halutsa site (Negev Desert, Israel). Results of the quantitative interpretation for (C) profile I-I and (D) profile II-II. (+) Position of the middle of upper edge of anomalous body for magnetic anomaly. ⊙ Upper edge of anomalous body for the SP anomaly. This figure is available in colour online at wileyonlinelibrary.com/journal/arp 131 Estimating Informational Content C, expenditure; T, time. Expenditure and time units are for geophysical survey in an area of 10 × 10 m with a grid of 1 × 1 m. The calculation of variables C and T includes geophysicists' salaries, amortization (rent) of magnetometric and self-potential equipment and time. 132L. V. Eppelbaum Figure 5. Archaeological site Nahal Hagit (northern Israel): (A) observed magnetic map; (B) magnetic map from (A) transformed using an entropy parameter. This figure is available in colour online at wileyonlinelibrary.com/journal/arp 135 Estimating Informational Content

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