ABSTRACT
Ground effects have been an integral part of intensity (I) assessment since introduction of the first scale by de Rossi and Forel in 1883. However during the first half of this century an enormous amount of work has been devoted to improving I scales through a detailed classification of the different types of buildings and expected damage. As an extreme culmination of this tendency, the recent up-dated EMS 92 macroseismic scale completely ignores ground effects, only listing them in a short Appendix. Although this approach is reasonable for densely urbanized areas, it does not reflect the full meaning of the I parameter, it docs not work for I assessment in the highest degrees of the scales, it is unsuitable in remote areas and cannot be used for comparison of historical events and seismic hazard evaluation in areas affected by strong events with return periods longer than the historical records. On the other hand, worldwide studies on the empirical relations between seismic parameters and ground effects demonstrate that, even if type and relevance of surface effects strongly depend on the local geomorphological setting, their definition allows a realistic estimation of the earthquake size. In this paper these relations are briefly discussed and preliminary proposals are given for the better use of ground effects in I assessment.
