Relationships between ground motion parameters and macroseismic intensity for Italy

Augusto Antonio Gomez-Capera,Marco Santulin,Mario Locati,Giovanni Lanzano,Maria D’Amico

doi:10.1007/s10518-020-00905-0

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, peak ground velocity, spectral acceleration at 0.2, 0.3, 1.0 and 2.0 s from the ITalian ACcelerometric Archive (ITACA; Luzi et al. in Italian Accelerometric Archive v3.0, Istituto Nazionale di Geofisica e Vulcanologia, Dipartimento della Protezione Civile Nazionale, 2019. https://doi.org/10.13127/itaca.3.0), and macroseismic intensity at Mercalli–Cancani–Sieberg (MCS) scale from the database DBMI15 (Locati et al. in Database Macrosismico Italiano (DBMI15), versione 2.0, Istituto Nazionale di Geofisica e Vulcanologia (INGV), 2019. https://doi.org/10.13127/DBMI/DBMI15.2). A dataset is 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 correlates strong motion stations and macroseismic intensity observations generally within 2 km from each other, and each association is manually validated through an expert judgement. 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–IMCS–GMP and the associated standard deviations are compared with previous models. In order to verify the proposed model, a map in terms of PGA is obtained, starting from the PSHA in terms of intensities (Gomez Capera et al. in Bull Seismol Soc Am 100(4):614–1631, 2010. https://doi.org/10.1785/0120090212) and then using the empirical relationship here proposed in PGA, and compared with the National Italian seismic hazard map (Stucchi et al. in Bull Seismol Soc Am 101(4):1885–1911, 2011. https://doi.org/10.1785/0120100130).

Highlights

Macroseismic intensity is considered a classification of the severity of ground shaking on basis of observed effects in a limited area (Grünthal 1998), and it encompasses the effects of different factors that characterize the destructive potential, such as the peak parameters, the frequency content, and the duration of the ground-motion, the soil-structure interaction, the inelastic response of buildings, and so on (Trifunac 1991; Sokolov and Chernov 1998; Atkinson and Sonley 2000; Boatwright et al 2001)
The main issue relates to their high variability and is essentially due to the different spatial representativeness of the two ground shaking measures: the instrumental one is restricted to few hundreds of meters in the vicinity of the recording station and strongly depends on local site effects; on the other hand, the macroseismic observations that contribute to assigning to a locality an intensity level is carried out on an extended inhabited area, often placed on a composite substrate with different geological, geomorphological, and topographic characteristics (Trifunac and Westermo 1977; Trifunac and Lee 1992; Theodulis and Papazachos 1992)
As instrumental measures of the seismic shaking, we have considered the geometric mean between the two horizontal components of peak ground acceleration (PGA), peak ground velocity (PGV) and spectral accelerations (SA) at 0.2, 0.3, 1.0, and 2.0 s

Summary

Introduction

Macroseismic intensity is considered a classification of the severity of ground shaking on basis of observed effects in a limited area (Grünthal 1998), and it encompasses the effects of different factors that characterize the destructive potential, such as the peak parameters, the frequency content, and the duration of the ground-motion, the soil-structure interaction, the inelastic response of buildings, and so on (Trifunac 1991; Sokolov and Chernov 1998; Atkinson and Sonley 2000; Boatwright et al 2001). The main issue relates to their high variability and is essentially due to the different spatial representativeness of the two ground shaking measures: the instrumental one is restricted to few hundreds of meters in the vicinity of the recording station and strongly depends on local site effects; on the other hand, the macroseismic observations that contribute to assigning to a locality an intensity level is carried out on an extended inhabited area (even several square kilometres), often placed on a composite substrate with different geological, geomorphological, and topographic characteristics (Trifunac and Westermo 1977; Trifunac and Lee 1992; Theodulis and Papazachos 1992) Despite this limitation, empirical relationships between macroseismic intensity and instrumental ground motion parameters (GMPs) are largely used, since they are one of the key elements for comparing seismic hazard assessment (SHA) in GMP to SHA in terms of macroseismic intensities (Gomez Capera 2006; Gomez Capera et al 2007) and for shakemaps implementation (Kaestli and Faeh 2006; Michelini et al 2008; Wald et al 2006; Allen and Wald 2009; Faenza and Michelini 2011).

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