Macroseismic intensity attenuation models calibrated in Mw for Italy

Abstract

This study aims at developing new macroseismic intensity attenuation models valid for Italy by exploiting the most updated macroseismic dataset and earthquakes catalogue, as well as the information obtained from a critical analysis of the most recent models in the literature. Several different attenuation models have been calibrated as a function of the moment magnitude ( Mw ) and epicentral distance from 16,260 intensity data points, that are related to 119 earthquakes occurred after 1900. According to trends and residuals analysis, the preferred calibrated intensity attenuation function is a Log-Linear model for epicentral distance ( R epi in km) and a linear model for Mw as: $$I\left( {MCS} \right) = {1}.{81} - {2}.{61}LogR - 0.00{39}R + {1}.{42}Mw$$ I MCS = 1.81 - 2.61 L o g R - 0.0039 R + 1.42 M w with pseudo hypocentral distance $$R = \sqrt {R_{epi}^{2} + \left( {9.87} \right)^{2} }$$ R = R epi 2 + 9.87 2 ; the estimated standard deviation is σ = 0.75. Also noteworthy is another model for macroseismic intensity attenuation that proved to be as good as the best model and shows higher sensitivity to physical parameters, such as focal depth and magnitude, especially in the epicentral area. Performance of all calibrated models was also checked on an independent set of 15 post-1900 Italian earthquakes. One of the results of the present work is the opportunity to define earthquake scenarios (e.g. probabilistic seismic hazard maps) in terms of Macroseismic Intensity and its related standard deviation, avoiding the uncertainties due to the conversion of various ground shaking parameters into intensity values.

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