Comparison of five independent catalogues of earthquakes of a seismic region

• Published in: Geophysical journal international 2000-11, Vol.143 (2), p.417-426
• Main Author: Caputo, Michele
• Format: Article
• Language: English
• Subjects: earthquake catalogues; seismic regions; seismic risk
• ISSN: 0956-540X; 1365-246X
• DOI: 10.1046/j.1365-246X.2000.01235.x

In order to evaluate the reliability of estimates of risk from rare events it is crucial to establish the dependability of historical data. In this paper we present a statistical comparison of a unique set of data covering 1000 years consisting of five independent catalogues of earthquakes in the Italian region. We selected the 78 earthquakes that are evaluated with intensity X or more in at least one of the catalogues and not less than VII in all the catalogues, and computed the average intensity and the standard deviations of the intensities. We find that the standard deviations increase significantly with the age of the earthquakes. Tables with the number of earthquakes that have the same intensity in a given number of catalogues, including the 10 possible couples of catalogues, are also presented and discussed with the purpose of studying the consistency of the five catalogues. We find, amongst other things, that two events out of three, of the 78 considered, have the same intensity in at least three catalogues, and 12 per cent of them have the same intensity in all catalogues. Comparisons with previous studies of the catalogues are also made, and their results confirmed. The lack of resolution of the intensity scales is shown numerically. It is verified that there is an apparent discontinuity in the frequency of occurrence of destructive earthquakes in the 17th century, and also that there is an apparent imbalance of energy release in the second part of the 20th century.