The UNDP/ UNESCO Survey of the Seismicity of the Balkan Region has given first priority to the compilation of an earthquake catalogue. The catalogue represents a collection of main earthquake parameters and serves as a basis for any kind of seismicity investigation.

Naturally, in 1970, when the work began, various national and international catalogues existed and this enabled us to proceed relatively quickly with the the task. It was however felt that a further progress could be reached, particularly as concerns the macroseismic information and its treatment, should a new regional catalogue be compiled.

The Project Office organized two meetings on earthquake cataloguing, one in December 1970 in Skopje and one in November 1971 in Belgrade. During the meetings, the principles for the compilation of the catalogue were discussed and adopted. The principal target was to reach the homogeneity of the original information in time, space and a certain magnitude range. Following the recommendations, the national experts prepared catalogues in the form of lists of parameters accompanied by isoseismal maps, whenever possible.

All national experts are listed together with Dr. N. V. Shebalin, Unesco expert in cataloguing as authors of the final catalogue because their contributions form the basis of it. The main task for Dr. N.V. Shebalin, was to compare and complete the accumulated information and to get finally a set as homogeneous as possible. During the preparation of the Catalogue in its final form, he classified the accuracy of the origin time and focal coordinates using their dispersion and changed or completed some parameters such as epicentre coordinates and intensity, in a uniform way. The unique availability of the large set of isoseismal maps enabled Dr. Shebalin to estimate the depths of foci for all shocks, using average isoseismal radii and his empirical ( M, I, r)-relations. The first draft of the catalogue was discussed with national experts during the missions of Dr. Shebalin to individual countries and on some other occasions. The final changes of the editor could not be presented because the manuscript was completed in June 1973 and had to be prepared for printing.

The catalogue 1901-1970 (M'4 or I >VI) has two appendices, the first one with additional shocks discove?ed later, and the second one containing weak shocks which, although not complete, represent a very valuable information for seismological analysis.