Ground-Motion characterization and modeling of the 2016 Central Italy earthquake sequence

Abstract

Central Apennines is one of the most seismically active areas in Italy, where a long history of earthquake (69 events with magnitude 5.0 or greater, and 7 with magnitude exceeding 6.0) has strongly influenced the development of earthquake-resistant structural design. The Amatrice earthquake with a magnitude of 6.0 has occurred on August 24th, 2016 at 1:36:32 UTC and heavily damaged the villages of Amatrice and Accumoli. In following five months nine seismic events with magnitude M>5.0 occurred in the area. The largest event of the sequence (M6.5) occurred on October 30th at 06:40:18 UTC with the epicenter located in the vicinity of the town of Norcia. The sequence in progress together with that of L'Aquila (6 April 2009) provides a massive set of seismological data (3 events with magnitude 6.0, up to a maximum magnitude 6.5. The main objective of this study is to provide the quantification of the ground motion induced by a given earthquake that may have effects on the territory. Therefore, we obtain the scaling relationships for the high frequency ground motion in the region and regressions were carried out over 91,000 selected waveforms recorded during 672 events with magnitude ranging from Mw3.0 to Mw 6.5. For sequence we both use accelerometric and seismometric data recorded by the seismic stations of the National Accelerometric Network (RAN) and the National INGV Seismic Network (RSN). Regional attenuation and source scaling are parameterized to describe the observed ground motions as function of distance, frequency and magnitude. Peak ground velocities are measured in the selected narrow frequency bands from 0.25 to 20.0 Hz; observed peaks are regressed to define a regional attenuation function, a set of excitation terms and a set of site response terms. Results are then modeled through the random vibration theory. Finally, these set of parameters (frequency dependent attenuation, source and site related spectral parameters) are performed in order to predict the earthquake-induced ground motion in the region and then validated against recordings. We also compare our predicted ground motion parameters with recent global and regional ground motion prediction equations and reveal the importance of the retrieving specific regional seismic parameters for the ground motion predictive equations.