The first part of the catalogue of earthquakes M > or IO > VI MSK which originated in the European-Mediterranean area in 1901-1955, was compiled during the years 1960-1967 (Kárník, 1968). It originated as part of a project of the Sub commission Seismicity of the European Seismological Commission (ESC).

The main goal was to achieve the maximum possible homogeneity of the catalogue in time, space and magnitude. The principles and methods developed and applied for this purpose have been described in several Progress Reports and in two volumes of the Seismicity of the European Area (Kárník, 1968, 1971). The main achievement of the work done was the uniform determination of magnitudes of all catalogued earthquakes. In principle, magnitudes based on amplitudes of surface waves (L/?, Lg/Sg) were determined for all shallow earthquakes (Л <60 km), whereas amplitudes of body waves (P, S) served for magnitude determination of shocks deeper than normal. This procedure allowed the first objective comparisons of earthquake activity in different earthquake regions of the European area, several statistical analyses to be produced, and epicentre maps and the map of seismic energy to be compiled.

Other catalogued parameters, i.e. origin time H, epicentral coordinates, depth of focus h, maximum observed intensity Imax, or epicentral intensity Io, radii of isoseismals were not systematically recalculated or revised, but parameters reported in national catalogues or by international centres were mostly adopted after being checked to the extent possible. Most changes were made in the values of h, rn and Io, however, the uniformity of their determination could not be maintained for all events. The focal depth determination has remained a problem to date, particularly for events originating within the lithosphere. A reliable depth determination can be guaranteed only by dense local networks, but such coverage exists only in few focal regions and is not feasible in oceanic areas. Focal depths h <60 km in the first catalogue were estimated from mean radii of isoseismals (Kárník, 1968,1971), values h ≥60 km and all depth determinations after 1955 correspond to determinations of seismological centres, or to those reported in national catalogues.

The importance of reliable seismological data bases has been increasing since 1960, mainly because of growing requirements for seismic hazard assessments on regional or local scales. This development revived the interest in the data on historical earthquakes and stimulated many serious investigations of the quality of historical information as well as serious attempts to improve hazard assessment methods. The community of experts involved in seismicity, seismic hazard and seismic risk analyses is well aware of the fact that only a complete and homogeneous data base can guarantee reliable results. Conclusions drawn on the basis of heterogeneous sets can be misleading.

During 1970-1990 most European and Mediterranean countries revised and completed their earthquake catalogues. It was also felt that the European-Mediterranean catalogue of 1968 should be extended, and that the first part covering the years 1901-1955 should be revised with the use of newly available information from national catalogues and studies. The present volume is the result of work done during the years 1970-1980 and 1985¬-1992. In judging its quality, it should be emphasized that cataloguing of earthquake data is a never-ending process, because there will always be corrections, based on new studies, to be made in the future. Thus, all catalogues reflect the state of knowledge at the time of their compilation. Naturally, this conclusion also applies to the present 1901-1990 catalogue, version 1992, but this is not meant as an excuse for the errors made by the author.