ASMI Archivio Storico Macrosismico ItalianoItalian Archive of Historical Earthquake Data

The macroseismic studies of historical earthquakes have become, in recent years, of great interest and the Italian Geodynamic Project has promoted and encouraged them.

This renewed interest induced us to complete the researches on the seismicity of Sicily and Calabria -which started with the earthquake catalogue, Carrozzo et al (1975)- by compiling a catalogue of isoseismal maps for earthquakes which occurred in the period 1783-1978.

Data, already gathered during the preparation of the earthquake catalogue, have now been critically reinterpreted, so making possible the drawing of isoseismal maps of 142 events. Later on, as established among members of group «catalogo dei terremoti», a macroseismic study of earthquakes preceding 1783, with intensity greater than nine, will be carried out trying to find other original references and papers of contemporary authors.

The quality of data is not homogeneous. Only earthquakes of greater intensity have a remarkable number of information, nevertheless, earthquakes which had a poorer quality of information, but enough to define the macroseismic field, were included as well.

Criteria used in the catalogue

The degree of intensity has been assigned using the M.S.K.-64 scale.

This scale shows the advantage of giving separate criteria of assessment of the intensity, according to the description of three kinds of effects:

1. on buildings and man-made structures,
2. on ground and in the regime of ground water,
3. on people and their environment.

This permits the definition of the intensity with a good accuracy even when there are poor descriptions of the effects as often happened for old or low-intensity earthquakes.

The original description of damage by past authors, have been reinterpreted according to criteria of the M.S.K. scale; when this was not possible, due to lack of descriptions, the values of intensity, generally expressed according to the Mercalli scale, have been transformed into the corresponding M.S.K.-64 values, using the relationship.

I_M.S.K. = 0.94 I_M.M. + 0.08 (Cosentino-Lombardo, 1980)

As regards criteria used in drawing isoseismals, a simple contouring of points representing the estimated intensity was performed, this avoids any normalization of the macroseismic field and any subjective interpretation.

In some cases, mainly for events located in the etnean area, when there was lack of descriptions but it existed the isoseismals map drawn by the author according to his own survey, the mesoseismal area was faithfully reported.

The isoseismals of studied events have been grouped into 5 zones Calabria and Peloritani area, Sicilian coastal chain, Etna, Iblei and Belice with different seismic and structural characteristics, according to the preliminary results of studies on the seismotectonic zonation of Sicily and Calabria (Barbano et al., 1978; Barbano et al., in print).

The map in fig. A, besides, shows the macroseismic epicentres, estimated as barycentre of the mesoseismal area. The epicentres of earthquakes occurred in the sea were included as well, only if the trend of isoseismals allowed a rough location.