Seismic damage in historic town centres and attenuation criteria

The structural significance of the damage scenarios characteristic of VIII and IX degrees on the MKS macroseismic scale is discussed with reference to the seismic behaviour of the buildings which make up the urban fabric of a historic town or city. In an VIII degree scenario, damage is limited to structurally precarious situations, while a IX degree scenario involves seismic damage to external walls. Mechanical interpretation of these scenarios provides the basis for intervention strategies sufficiently well defined as to constitute a guide for seismic damage prevention programmes. VIII degree damage is prevented by identifying precarious situations. while IX degree damage requires systematic action. A proposal is put forward for the clarification of seismic regulations and the usefulness of evaluating future earthquakes in macroseismic terms with reference to the safety requirements of new buildings is discussed