Relationships between ground motion parameters and macroseismic intensity for Italy

Abstract

The relation between macroseismic intensity and ground shaking makes it possible to transform instrumental Ground Motion Parameters (GMPs) in macroseismic intensity and vice versa, and is therefore useful for making comparisons between estimates of seismic hazard determined in terms of GMPs and macroseismic intensity, and for other engineering and seismological applications.

Empirical relationships between macroseismic intensity and different recorded GMPs for the Italian territory are presented in this paper. The coefficients are calibrated using a dataset of horizontal geometrical mean GMPs, i.e. peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration (SA) at 0.2, 0.3, 1.0 and 2.0 s from the ITalian ACcelerometric Archive (ITACA; Luzi et al. 2019), and macroseismic intensity at Mercalli-Cancani-Sieberg (MCS) scale from the database DBMI15 (Locati et al. 2019). A dataset was obtained that corresponds to 240 pairs of macroseismic intensity-GMPs from 67 Italian earthquakes in the time window 1972-2016 with moment magnitude ranging from 4.2 to 6.8 and macroseismic intensity in the range [2, 10-11].

The final dataset is developed correlating strong motion stations and macroseismic intensity observations generally within 2 km from each other, but the associations is manually validated through the expert opinion. The adopted functional form is non-linear predicting macroseismic intensity as a function of LogGMPs and vice versa by performing separate regressions. The set of empirical conversion relationships GMP-I MCS -GMP and the associated standard deviations are compared with previous models.

The results of an illustrative PSHA, obtained using a new seismogenic zonation (Santulin et al. 2017), proposed as one of the inputs of the new Italian seismic hazard model (Meletti et al. 2017), are used to analyse and compare seismic hazard assessment in terms of PGA and the related seismic hazard map in terms of macroseismic intensity (MCS) obtained using the empirical relationships here proposed for the PGA.