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Several studies, conducted over the last 20 years, have shown that ground motion in Italy is characterized by a strong regional variability and, in particular, tectonic and geological factors play key roles in the definition of the observed differences. In the early 2000s, several researches (Castro et al. 1999, Malagnini et al., 2000; 2002) were focused on conducting systematic studies of the regionalization in Italy using local dataset of small magnitude recordings of the seismic sequences that occurred in Italy in the early instrumental epoch.Recently, the availability of a large number of records from moderate-to-strong earthquakes on the entire Italian territory allowed us to review previous results, with the final aim of producing a new generation of Ground Motion Models (GMM) models for the calibration of shaking scenarios. In this work, the analysis of the residuals (logarithm differences between observations and GMM predictions) was exploited to describe the regional differences in terms of source and path effects across the country (Brunelli et al. 2023), confirming the results of the previous studies conducted in Italy. Based on these results, we developed a regionalised model for Italy, using an approach similar to that of Kotha et al. (2020) for source effects, and a zoneless approach for propagation effects. We also improved the near-source predictions, integrating the dataset with records from the NESS database (https://ness.mi.ingv.it/), and through the introduction of the explicit dependence on focal depth., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Estimation of amplification factors (AFs) at the local or regional scale is an important task in land planning and seismic design, especially in areas with high seismic hazards and complex geological and geomorphological structures of the territory, such as Italy. When multiple seismic recordings at a single site are available, they can be exploited to estimate AFs empirically through many methods, such as: a) spectral ratios between i) the horizontal and vertical ground-motion components and ii) the shaking observed at the site and at a reference rock site, both for acceleration response and Fourier spectra; b) parametric or non-parametric generalized spectral inversion techniques; and c) decomposition of residuals of a nonergodic Ground Motion Model (Rodriguez-Marek et al., 2011; Priolo et al., 2020, among the others) to estimate repeatable within-site terms (δS2S). In this study, we exploited the estimates of δS2S provided by Lanzano et al (2022), through the ITACA (ITalian ACcelerometric Archive) web portal (https://itaca.mi.ingv.it/ItacaNet_32/#/products/itacas2s_flatfile), to compute the AFs for about 800 recording sites in Italy. We then compare AFs estimates with different proxies for predicting the site effects, such as Vs profile, resonance frequency, cover geology and topographic slope. Moreover, we also employed the empirical AFs to validate the estimates provided by 1D, 2D and 3D numerical modeling of the site response. Later, we investigate spatial correlation of the AFs in urban areas, where dense networks are installed., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Intensity Prediction Equations (IPEs) allow predicting the possible macroseismic intensity values at any site, as a function of epicentral distance and epicentral intensity or magnitude. In Italy, different approaches have been proposed in the last years for developing intensity attenuation models. We evaluated the performance of the five most recent IPEs valid for the Italian area comparing their predictions with intensities documented at Italian localities.We built two different testing datasets using the data contained in the most recent versions of the Italian Parametric Earthquake Catalogue CPTI15 and of the Macroseismic Italian Database DBMI15. Dataset 1 contains 213 earthquakes with instrumental location and magnitude from 1907 to 2020, whereas Dataset 2 includes 357 events that occurred from 1117 to 1978 with the epicentral parameters estimated from macroseismic intensity data. We computed the residuals between documented intensity values and predicted intensities using the IPEs. Analyzing these results as a function of the epicentre-to-site distance, of the values of documented intensities and of the magnitude of each considered earthquake, we observed a systematic underprediction for high intensity values in both datasets for all the considered IPEs.We also investigated the between-event residuals to highlight spatial and temporal patterns. The results did not show any particular spatial trends, but a significant temporal dependence of the results for Dataset 2, with an underestimation of the documented values for all the considered IPEs for earthquakes in the period 1000-1700., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

We describe the main structure and outcomes of the new probabilistic seismic hazard model for Italy, MPS19 [Modello di Pericolosità Sismica, 2019]. Besides to outline the probabilistic framework adopted, the multitude of new data that have been made available after the preparation of the previous MPS04, and the set of earthquake rate and ground motion models used, we give particular emphasis to the main novelties of the modeling and the MPS19 outcomes. Specifically, we (i) introduce a novel approach to estimate and to visualize the epistemic uncertainty over the whole country; (ii) assign weights to each model components (earthquake rate and ground motion models) according to a quantitative testing phase and structured experts’ elicitation sessions; (iii) test (retrospectively) the MPS19 outcomes with the horizontal peak ground acceleration observed in the last decades, and the macroseismic intensities of the last centuries; (iv) introduce a pioneering approach to build MPS19_cluster, which accounts for the effect of earthquakes that have been removed by declustering. Finally, to make the interpretation of MPS19 outcomes easier for a wide range of possible stakeholders, we represent the final result also in terms of probability to exceed 0.15 g in 50 years., peer-reviewed

The availability of high-quality waveforms recorded in epicentral areas of moderate-to-strong earthquakes is a key factor for investigating ground-motion characteristics close to the seismic source. In this study, near-source strong-motion waveforms (named NESS1) were collected from worldwide public archives with the aim of building a flat file of high-quality metadata and intensity measures (IMs) of engineering interest. Particular attention was paid to the retrieval of reliable information about event sources, such as geometries and rupture mechanisms that are necessary to model near-source effects for engineering seismology and earthquake engineering applications. The accelerometric records are manually and uniformly processed, and the associated information is fully traceable. NESS1 consists of about 800 three-component waveforms relative to 700 accelerometric stations, caused by 74 events with moment magnitude larger than 5.5 and hypocentral depth shallower than 40 km, with Joyner-Boore distance up to 140 km. Ground-motion data were selected to have a maximum source-to-site distance within one fault length, defined through seismological scaling relations. About 40 records exhibit peak acceleration or peak velocity exceeding 1g or 120 cm=s, and they represent some of the largest ground motion ever recorded. Evidence of near-source effects was recognized in the NESS1 dataset, such as velocity pulses, large vertical ground motions, directional and hanging-wall amplifications and fling step. In particular, around 30% of the records was found to exhibit pulse-like characteristics that are possibly due to forward rupture directivity. Electronic Supplement: Table listing the main features of the selected events, including the references of fault geometry parameters and Figures showing further metadata and intensity measures distributions of the NESS1 flat file.

The paper summarizes the preliminary results of 1D and 2D seismic site response analyses addressed to the seismic characterization of four accelerometric stations of the RAN (Italian Accelerometric Network) located along an array in the Sulmona alluvial basin, Abruzzo (Italy). The main uncertainties about the morphological and geotechnical soil model of the array concern the morphology and depth of the bedrock and the value of shear wave velocity, VS, at depths greater than 30m. To overcome these difficulties the available geological survey, boreholes, and field geophysical tests, including HVSR and SSR measurements from noise and aftershocks, one cross hole (CH) and two down hole (DH) tests were collected and integrated. The results of the elastic site response analyses at the RAN stations were compared with two recorded events of the Central Italy seismic sequence (24.8.2016 Mw= 6.0 and 30.10.2016 Mw=6.5 earthquakes) in terms of response spectra, amplification factors of peak ground acceleration and spectral intensity. The results revealed that the response towards the middle of the basin is about one-dimensional, while the response at the two stations closer to the border of the valley is significantly affected by the buried morphology of the tectonic contact between the sedimentary soils and the fault rock slope.