Macroseismic intensity evaluation with the <<Fuzzy Sets Logic>>

Abstract

The use of a macroseismic scale often requires subjective choices and judgments which may produce inhomogeneities and biases in the resulting intensities. To get over this problem it would be necessary to formalize the decision process leading to the estimation of the macroseismic intensity but, on historical records, this is often hindered by the poorness and incompleteness of the aLailable information and by the intrinsical ambiguity of the common language. Moreover. all the intensity scales have always been created and updated to be used <<in the field. on contemporary earthquakes and then it may happen tkdt even detailed historical descriptions often do not correspond to the descriptive frameworks of any grade. I11 order to face these problems. we propose in this work a computer method for the evaluation of the macroseismic intensity which makes use of the <<Fuzzy Sets Logic>>T. his approach reproduces the taslts performed by the hurnan brain which. taking advantage of the tolerance of imprecision. is able to handle with information bearing only an approximate relation to the data. This allows to understand and make explicit some passes of the evaluation process that are unconsciously followed by the macroseismic exper