Empirical Ground Motion Models in Italy: from the earthquake recordings to a regionalized model

ABSTRACT: Ground Motion Models (GMMs) are empirical equations to estimate ground motion Intensity Measures as a function of several variables, generally related to the seismic source (e.g. magnitude), source-to-site distance (e.g. epicentral, hypocentral, Joyner-Boore distance, among others) and local site conditions (e.g. site categories or averaged shear wave velocities in the uppermost 30 meters). Traditionally, due to the scarcity of regional data, ground-motion models (GMMs) were developed under the ergodic approach, which assumes the statistical properties of the ground-motion parameter do not change in space resulting in GMMs with stable median estimates but large aleatory variability. In recent years, as the size of available data has been increasing increased, the ergodic assumption can be relaxed. This led to the introduction of non-ergodic ground-motion models where repeatable effects related to the source, path, and site can be appropriately modeled, and separated from the aleatory variability. The presentation illustrates how create a regional data set from public webservices and websites, calibrate ergodic and non-ergodic GMM through a residual analysis and decomposing the residuals into repeatable terms. Based on the spatial trend of the interpolated residuals, and geological and seismological considerations, a zonations is proposed in the perspective of supporting regionalization of a future generation of GMMs for Italy. The reduced aleatory variability can impact the seismic hazard, especially at large return periods which is important for critical infrastructure.

BIO: Lucia Luzi is a Research Director at the National Institute of Geophysics and Volcanology (INGV) and, since 2019, she has been the Director of the Milan section of INGV. She earned her Bachelor's degree in Geological Sciences from the University of Camerino in 1991 and a Master of Science degree in Geological Survey from the University of Twente in the Netherlands in 1994. Over the years, her research has focused on seismic hazard, particularly the development of predictive models for ground motion, the study of site effects and seismic microzonation, and seismic-induced landslide hazard.
She has held international coordination roles, serving as the Secretary-General of ORFEUS (Observatories & Research Facilities for European Seismology) and Chair of the Strong-Motion Management Committee at ORFEUS. She has coordinated Work Packages for European projects on seismology and seismological infrastructures (e.g., NERA, SERA, EPOS-IP) and led projects and research units funded by the Department of Civil Protection. She designed the Italian (ITalian ACcelerometric Archive) and European (Engineering Strong-Motion Database) accelerometric databases. She represented INGV in the Joint Research Units of EPOS-Italia and sits on the scientific councils of Eucentre and the REDI consortium. She is the author and co-author of approximately 90 articles in international journals.