This volume is published as Part III of the Catalogue of Earthquakes of the Balkan Region which was issued in April 1974 as a basic collection of main earthquake parameters. Realizing the importance of isoseismal maps for further studies, the participating countries we're invited, at the very beginning of the project activities in December 1970, to make every effort to collect or compile as many isoseismal maps as possible. The response was very encouraging and more than 50.0 isoseismal maps were collected, of which 454 were finally selected for printing.

Dr. N. V. Shebalin, UNESCO expert in cataloguing, acted as editor of this volume. He checked all maps and completed or recompiled some of them; he also generalized the shape of all isoseismals for further application in determining the intensity- attenuation curves and in calculating focal depths. The original isoseismals drawn by national experts are preserved, the generalized isoseismals of Dr. Shebalin being drawn by thin lines. The maps covering more than one country required comparison and combination of individual sections. Technical problems related to these Operations are described by Dr. Shebalin in his explanatory text to the Catalogue for the years 1901-1970 (Part I, pp. 22-23).

As can be seen in the Atlas, there is no uniformity in the way of drawing isoseismals; some authors prefer a very detailed shape respecting every observation point, others prefer some kind of generalization of the macroseismic field and emphasize its main features rather than local variations of intensity. There are certain good reasons behind both approaches related to the further use of isoseismal maps. The most valuable are the maps on which the individual intensity data are plotted; they prevail in the Atlas and everybody can interpolate the isoseismals according to need, opinion and other factors.

The maps are disposed in chronological order which is sometimes slightly disturbed for technical reasons; therefore a list of maps and corresponding pages follows the Foreword. The key of each map indicates the basic earthquake parameters, symbols used, authors and the scale. A large portion of the maps had to be redrawn and this work was carefully done by Mr. I. Todorov at the Project Office.

All originals were drawn on scale 1:1 million, however, for printing purposes, the size of all maps was reduced proportionally from 1:2 to 1:4 approximately. The lay-out of the maps and all technical printing problems were arranged by Mr. V. Andjelkovic.

The present set of maps represents a unique collection of basic seismological information and all those who contributed to its preparation and printing deserve appreciation for their devoted and efficient work.