Ground-motion prediction equations (GMPEs) have recently been developed in the Next Generation Attenuation (NGA) project for application to shallow crustal earthquakes in tectonically active regions. We investigate the compatibility of those models with respect to magnitude scaling, distance scaling, and site scaling implied by Italian strong motion data. This is of interest because (1) the Italian data are principally from earthquakes in extensional regions that are poorly represented in the NGA dataset, and (2) past practice in Italy has been to use local GMPEs based on limited datasets that cannot resolve many significant source, path, and site effects. We find that the magnitude scaling implied by the Italian data is compatible with four NGA relations. However, the Italian data attenuate faster than implied by the four NGA GMPEs at short periods; the differences are statistically significant. Comparison with the fifth one was not possible because it was developed for rock conditions only. Three regression coefficients are reevaluated for the four NGA GMPEs to reflect the faster attenuation: a constant term, a term controlling the slope of distance attenuation, and a source fictitious depth term. The scaling of ground motion with respect to site shear wave velocity is consistent between the NGA models and Italian data. Moreover, the data are found to contain a nonlinear site effect that is generally compatible with NGA site terms. The intraevent scatter of Italian data is higher than in the NGA models, although interevent scatter is comparable to NGA recommendations when the faster distance attenuation is considered. On the basis of these findings, we recommend using the NGA relations, with the aforementioned minor modifications, to evaluate ground motions for seismic hazard analysis in Italy.

The central Italy earthquake sequence has, to date, generated three mainshocks:M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. These events, along with aftershocks, were well recorded by Italian networks, and are among the normal fault earthquakes with the highest number of recordings globally. We process records for six events using NGA/PEER procedures. Many recording sites lacked VS30 assignments, which we provide using measured shear wave velocity profiles where available and a local geology proxy otherwise. Stations at close distance, including near the hanging wall, exhibit fling step in some cases but no obvious rupture directivity. The data exhibit fast anelastic attenuation at large distances (>100 km), as predicted by recent Italy-adjusted global models, but not by Italyspecific models. We partition residuals from Italy-adjusted global models, finding negative event terms at short periods (weaker than average shaking). We apply Kriging of within-event peak acceleration and velocity residuals using a global semi-variogram model to estimate the spatial distribution of peak accelerations, which are generally most intense south-west of Mt. Vettore.

We describe an Italian database of strong ground motion recordings and databanks delineating conditions at the instrument sites and characteristics of the seismic sources. The strong motion database consists of 247 corrected recordings from 89 earthquakes and 101 recording stations. Uncorrected recordings were drawn from public web sites and processed on a record-by-record basis using a procedure utilized in the Next-Generation Attenuation (NGA) project to remove instrument resonances, minimize noise effects through low- and high-pass filtering, and baseline correction. The number of available uncorrected recordings was reduced by 52% (mostly because of s-triggers) to arrive at the 247 recordings in the database. The site databank includes for every recording site the surface geology, a measurement or estimate of average shear wave velocity in the upper 30 m (Vs30), and information on instrument housing. Of the 89 sites, 39 have on-site velocity measurements (17 of which were performed as part of this study using SASW techniques). For remaining sites, we estimate Vs30 based on measurements on similar geologic conditions where available. Where no local velocity measurements are available, correlations with surface geology are used. Source parameters are drawn from databanks maintained (and recently updated) by Istituto Nazionale di Geofisica e Vulcanologia and include hypocenter location and magnitude for small events (M 5.5) and finite source parameters for larger events

The Central Italy earthquake sequence nominally began on 24 August 2016 with a M6.1 event on a normal fault that produced devastating effects in the town of Amatrice and several nearby villages and hamlets. A major international response was undertaken to record the effects of this disaster, including surface faulting, ground motions, landslides, and damage patterns to structures. This work targeted the development of high-value case histories useful to future research. Subsequent events in October 2016 exacerbated the damage in previously affected areas and caused damage to new areas in the north, particularly the relatively large town of Norcia. Additional reconnaissance after a M6.5 event on 30 October 2016 documented and mapped several large landslide features and increased damage states for structures in villages and hamlets throughout the region. This paper provides an overview of the reconnaissance activities undertaken to document and map these and other effects, and highlights valuable lessons learned regarding faulting and ground motions, engineering effects, and emergency response to this disaster.