GNGTS 2017 - 36° Convegno Nazionale

GNGTS 2017 S essione 1.1 33 Fig. 2 - Close-up on the epicentral area and comparison with the equations of Gasperini (2001). In Fig. 2 we compared our dataset with the general equations by Gasperini (2001). The most striking difference is in the near-field: here, the ESI-based regression mimics the results of Gasperini whereas MCS data show the same slope, but higher ΔI values. We explore two possibilities for explaining the underestimation of MCS scale in the near- field: (i) the saturation at higher degrees and (ii) the presence of significant differences when comparing events occurred several centuries apart from each other. The former hypothesis is time-independent, while in the latter case a time-dependent behavior is expected. Thus, we divided the database into subsets, according to the timing of earthquake occurrence. We found a clear mismatch between MCS post-2000 (i.e., L’Aquila 2009 and Amatrice 2016 events) and previous events, which suggests the reliability of the second hypothesis. Conclusions and perspectives. MCS and ESI scales show opposite strength and limitations, which are counterbalanced when the two datasets are considered together. ESI scale is more robust in the near-field and possibly in evaluating epicentral intensity, I 0 , while MCS behaves better in the far-field. We suggested the existence of a bias in intensity assessment withMCS scale for contemporary earthquakes in respect of older ones. We argue that the integration of effects on the natural and the human environment is the best approach to assess overall earthquake intensity. Our results prompt to the need for a reassessment of earthquake effects in a renowned perspective, assuring the consistency between modern and historical events. The preliminary results described here look particularly promising and future developments include the following issues: - ��������� ���������� ����� ��� � ���� �������� ���������� �� ������ ��� ������������� different functional forms and a more accurate assessment of errors and uncertainties should be performed; - ��� ���� ���������� ������ ��� ������� ��� ������� ���������� ���� �� �� �������� �� ����� new case histories, within and outside the Italian Apennines, need to be analyzed to widen the available database and different tectonic regimes should be considered as well; - ����������� �� ��������� ���������� ��� ������������� ���� ���� ���� ������������� ������� development of surveying strategies and methodologies that take into consideration effects on buildings and the natural environment; - ���������� ��������� ������ �� ���� �� ������ �������������� ������� ����� ������� particular attention should be paid to recent (instrumental) events, which provide independent estimates of magnitude. This will enable to relate magnitude with ESI and MCS data, and to derive better magnitude estimates for pre-instrumental events, in analogy to the current practice, which is based on traditional scales only.