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The increasing number of records in the last years allows us a detailed statistical analysis of the strong motion data. In this study we would like to present a Regional and site-specific approach thanks to a huge and high quality accelerometric dataset for all the Italian territory of more of 120000 waveforms up to 150 km for more than 2300 events occurred in a time-span 2009-2017. This huge dataset allows us to regionalize the GMPEs, dividing the Italian territory in three parts, estimating for each part a different GMPE, for an expanded range of ground motion parameters such as: peak ground parameters (displacement, velocity and acceleration), the pseudo spectral accelerations at different periods (0.3, 1.0 and 3.0 seconds) and Arias and Housner intensities. In particular we study the 2016-2017 Central Italy sequence, in which many records for single stations are collected and site-specific GMPEs estimated. The resultant GMPEs are tested using an independent testing database and used as setup of the configuration of a near real-time ShakeMap system.

We use a multidisciplinary approach to gather preliminary evidence for a Quaternary east-dipping extensional detachment in Central Italy. This structure crops out in the Sabini-Eastern Simbruini (SES) and would be hidden at mid-crustal depths beneath the L'Aquila 2009 (Mw6.3) epicentral area. The SES geometry is reconstructed through geological mapping, structural analysis and seismic line interpretation. The geometry of the mid-crustal segment, referred to as the Ocre Segment (OS), is interpreted through seismological analyses of the largest aftershock (Mw5.4) of the L'Aquila 2009 sequence. The kinematic compatibility between the SES and the OS under a common SW–NE tensional field is tested through stress inversion of both geological and seismological data. The reliability of OS activation is tested through slip tendency analysis. Like other Italian cases, the SES and the OS are preliminarily interpreted as expressions at different depths of the same unknown east-dipping extensional detachment, characterized by a ramp–flat–ramp geometry.

On September 27, 2012 at 01:08 (UTC) a M L 4.1 earthquake started a seismic sequence approximately 10 km east of the city of Benevento, in Southern Apennines (Italy). During the following four days, about 40 events with M L ranging between 1.3 and 4.1 were detected in the same area, where the seismic hazard is one of the largest of the Italian Peninsula and where several historical and destructive events took place. In order to investigate the seismicity spatio-temporal pattern and to identify the seismogenic source geometry, a detailed analysis was performed integrating data recorded at three different seismic networks. The earthquakes were relocated using the double-difference technique and focal mechanism solutions were obtained by the moment tensor inversion. Also, to better understand the rupture process, seismic source parameters were estimated and apparent source time functions were inverted to retrieve the slip distribution for the largest magnitude event. Our results show the existence in the study area of roughly E–W striking fault plane with a right-lateral strike-slip kinematics, seated at mid-crustal depths (10–20 km), revealing a characteristic seismicity quite different from that typically associated to the outcropping NW–SE-striking active normal faults that are responsible of moderate to large earthquakes in the Southern Apennines axial sector. In this work, we address questions concerning i) the presence in the Benevento area of a mid-crust seismogenic strike-slip fault, previously unrecognized; ii) its link to the regional seismotectonic setting; and iii) the existence of a strike-slip tectonic regime that uniformly extends in the footwall of the Apennines thrust at relevant depth, not only in the Apulian foreland, as demonstrated to date, but also under the mountain chain axial zone.

A complex seismic sequence characterised by two thrust earthquakes of magnitudes M $$_\mathrm{L}$$ 5.9 and M $$_\mathrm{L}$$ 5.8 occurred on May 20 and 29, 2012, respectively, and activated the central portion of the Ferrara Arc structure beneath the Po Plain in northern Italy. The sequence, referred to as Emilia 2012, was recorded by the Italian Strong Motion Network, the Irpinia Network, the Friuli Venezia Giulia Network and 15 temporary stations installed by the Civil Protection Department. In this study, we compile and analyse a large dataset that contains 3,273 waveforms from 37 $$M_\mathrm{L} \ge 4.0$$ seismic events. The main aim of this paper is to characterise the ground motion induced by the Emilia 2012 seismic sequence and compare it with other data in the Italian strong motion database and to the recent Ground Motion Prediction Equations (GMPEs) developed for northern Italy, all of Italy and Europe. This is achieved by (1) the computation and analysis of the strong motion parameters of the entire Emilia Strong Motion Dataset (ESMD) and (2) a comprehensive investigation of the May 29 event recordings in terms of time–frequency analysis, the ground motion parameters and the response spectra. This detailed analysis was made possible by the temporary Civil Protection Department stations that were installed soon after the May 20 event at several municipalities in the epicentral area. Most of the recordings are characterised by low-frequency content and long durations, which is a result of the thick sedimentary cover that is typical of the Po Plain. The distributions of the observed horizontal peak ground accelerations and velocities (PGAs and PGVs) with distance are generally consistent with the GMPEs. This is particularly true for the data from M $$_\mathrm{L} \ge $$ 5.0 (M $$_\mathrm{W}\ge $$ 5.0) events, though the data are scattered at distances beyond approximately 60–70 km and show faster attenuation than the European GMPEs. The horizontal components for the May 29 event at two near-fault stations (Mirandola and San Felice sul Panaro) are overestimated by all of the analysed GMPEs. In contrast, the vertical components, which played an important role in the shaking near the source, are underestimated. The May 29 event produced intense velocity pulses on the horizontal components and the highest peak ground acceleration ever recorded in Italy on the vertical component of the Mirandola near-fault station. The ground motion recordings contained in the ESMD significantly enrich the Italian strong motion database. They contribute new information about (1) the possibility of exceeding the largest recorded PGA in Italy, (2) the development of a spectral design that takes into account the role of the vertical component and the extreme variability of the near-fault ground shaking, and (3) the characterisation of the ground motions in deep sedimentary basins.