GNGTS 2018 - 37° Convegno Nazionale

290 GNGTS 2018 S essione 2.1 The approach is to relate linearly the logarithm of GMP and macroseismic intensity as the only independent variable (Tselentis and Danciu, 2008; Bilal and Askan, 2014), thus relationships are independent of magnitude and/or distance. The ordinary least squares linear regression is used to obtain preliminary empirical equations. Modelling and conclusions. A data set was obtained that corresponds to 127 pairs of macroseismic intensity-GMP from 55 Italian earthquakes in the time window 1976-2016, with Mw ranging from 3.9 to 6.9 and macroseismic intensity I in the range [3-4, 11]. For each macroseismic intensity level, the mean and the dispersion of LogPGA are plotted in Fig. 1. In this figure, the irregular distribution of the data is observed. There are few GMP values for intensity I≥8 and even less in the classes lower than 5, while a large number of GMP values are available in the intensity range 5-6. A large scatter and gaps are observed for intensity 7. The obtained preliminary empirical relationship is: LogPGA = 0.50 + 0.23 I (σ = 0.18) (Fig. 1) I = -1.25 + 3.96 LogPGA (σ = 0.75) (Fig. 2) References Bilal, M., and Askan A. (2014). Relationships between Felt Intensity and Recorded Ground-Motion Parameters for Turkey. Bull. Seismol. Soc. Am . 104:1:484–496. Cua G., Wald D.J., Allen T.I., Garcia D., Worden C.B., Gerstenberger M., Lin K., Marano K. (2010) Best Practices for Using Macroseismic Intensiy and Ground Motion Intensity Conversion Equations for Hazard and Loss Models in GEM1. GEM Technical Repport 2010-4, GEM Foundation, Pavia, Italy, 59p. Fig. 1. The obtained empirical relationship: LogPGA as function of Macroseismic Intensity. Fig. 2.The obtained empirical relationship:Macroseismic Intensity as function of LogPGA . Time Range N. Events Mw Range I Range PGA (cm/s 2 ) Range N. Pairs (I,PGA) [1976-2016] 55 [3.9-6.9] [3/4-11] [5.36 – 915] 127 The following table summarizes the characteristics of the calibrated model: