Uncertainty and ambiguity of isoseismal maps

The problem of defining objective isoseismal maps is a yet unresolved. The aim of the work, here presented, is to show how the studies of different authors and eras can produce contrasting, even contradictory, interpretations of the macroseismic data set for the same earthquake. At this point in time, the principal macroseismic end (i.e. that which furnishes seismology, seismotectonics and studies of seismic risks with descriptions of the effects of earthquakes, as far as possible exempt from interpretation) is in danger of failing. Throughout this work, we have sought to bring to light how certain anomalies of macroseismis maps principally reside in the diversity of data interpretation, and how it is possible to put in evidence these by applying appropriate statistical analysis to the macroseismic fields. The Silician earthquake of 11 January 1683 (Io = XI) was taken as an example, as a sufficient quantity of information was available; a filter procedure was then applied to the macroseismic data. Finally we also show that such procedures are very useful in the treatment of border earthquakes, in an attempt to homogenize macroseismic fields from different countries.