ON FILTERING MAGNETIC SOURCES AT DEPTH, USING ANALYTIC CONTINUATION INTO THE FIELD OF EQUIVALENT SOURCES

Purpose. The paper considers the techniques and methods aimed at interpretating and specifying the location of the archaeological sites using the equivalent layer filtering approach. The task is to outline all the required anomalies (including small) per se and present them in a visual form. For this purpose, it is necessary to perform two procedures: remove the regional background and to filter noise. Design/methodology/approach. We studied the possibility of using filtration by means of analytical continuation in the top half-space as a way of separating sources at various depths. We offer the following algorithm of restoring potential field by the equivalent distribution of sources: Elimination of the regional field, Estimation of the residual field anomalies, Calculation of the magnetization, Filtering the anomalies. There are a number of assumptions made, and one must keep in mind that magnetic and gravity data contain no inherent information about the depth of source and the observed magnetic field to be the sum of the regional field, the residual field, and aggregate noise. We also used assemblages of mutually uncorrelated thin source distributions at various depths to model the field as equivalent source layers. Findings. Based on the analysis of the magnetic data survey acquired for a Pineview park of 30´80 m, we calculated upwards magnetic anomalies in order to perform their archaeological interpretation. An analytical continuation procedure allows us to divide the anomalies by the sources depths. Field calculation from the sources in an equivalent layer by means of calculating of the residual field from the anomalous sources boundaries allowed us to define the contours of the magnetic anomalies. Additional calculation of the horizontal gradient of magnetic induction allowed us to adjust the classification of local anomalies by the amplitude. Practical value/implications. The conducted research proves the necessity to create a general database on processing archaeological objects of geological heritage (geosites) of Ukraine under a single state program. The research was also successful in testing a method for analytical extension of components of a magnetic field into the field of equivalent sources within the sample data for Pineview park (30´80 m) to do their archaeological interpretation. Additional information used for the qualitative analysis is the calculation of the horizontal gradient of the magnetic induction in order to specify the classification of the local anomalies by the amplitude. The transformations above one can be complemented with other filters. The results of the interpretation are of qualitative character, nevertheless they us allowed us to localize the location of excavations.