Considerations on using MCS and EMS-98 macroseismic scales for the intensity assessment of contemporary Italian earthquakes

Abstract

The concept of macroseismic intensity arose with the purpose of measuring the strength of an earthquake by the effects it causes on buildings, people, and domestic furnishings. From this perspective, buildings can be considered seismic sensors that record the shaking. Early scales were conceived at a time when buildings were mainly in masonry and therefore they could be used as markers of the intensity in case of earthquakes. Indeed, since they were fairly homogeneous, their level of damage could be considered as an indicator of the shaking level. In recent decades, the evolution of construction techniques have made the MCS scale unsuitable for damage assessment of buildings of various resistance. To overcome this problem the EMS-98 scale was designed. Because the MCS scale is still used in Italy, even in the presence of many reinforced concrete buildings, the purpose of this work is to show that the EMS-98 is the most suitable tool for assessing intensity as it is more consistent with the built environment. Theoretical and real intensity assessments, by both MCS and EMS-98, have been determined and compared, showing that nowadays intensity is a function of the vulnerability. MCS and EMS-98 would be comparable only when the building stock is composed of very vulnerable edifices (generally class A). Finally, thanks to the similarity of the two scales for old and vulnerable buildings, EMS-98 appears fully adequate to investigate historical earthquakes and represents a powerful tool to ensure continuity among earthquakes of different epochs.