JOURNAL OF THE BALKAN GEOPHYSICAL SOCIETY, Vol. 1, No 4, November 1998, p. 53-59, 7 figs.

Calculation of the azimuthal inhomogeneity ratio response of

3-D structures using an analytical forward modelling scheme

K.M.Ermokhin *, G.N.Tsokas **, P. Tsourlos **, V.V. Glasunov*

*Geophysical Faculty, St.Petersburg Mining Institute, St.Petersburg, Russia

**Geophysical Laboratory, Aristotelian University of Thessaloniki, Thessaloniki 54006,Greece

(Received 17 September 1998; accepted 20 October 1998 )

Abstract: The Azimuthal Inhomogeneity Ratio (A.I.R.) can be obtained by measuring the three possible modes of connection for resistance measurements with the square array and it reflects the presence of subterranean lateral inhomogeneities. The A.I.R. anomalies form a signal of dipolar pattern and have relatively large amplitude.

The expected A.I.R. pattern of two models was computed in the framework of the present study together with the respective resistance anomalies for all three possible modes. The method of "dipole sources" was applied for the computation of the response of the 3-D models. The models that simulate the targets commonly encountered in archaeological exploration were selected to test the validity of the suggested method.

The calculated A.I.R. patterns delineate very well the edges of the disturbing bodies. Moreover, they present an intricate pattern suitable that can be handled by the pattern recognition schemes.

Key Words: Azimuthal Inhomogeneity Ratio, Resistivity Modelling, Dipole Sources.