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Con questo volume, che fa parte della collana BookMS Manuali (download dal sito www. centromicrozonazionesismica.it), intendiamo raccogliere, organizzare e mettere in condivisione i principali elementi e insegnamentitratti dall'intensa attività svolta in questi ultimi due anni. In particolare, sono riportate indicazioni utili alle attività di raccolta dati e relativa elaborazione per la realizzazione di carte di microzonazione sismica di livello3; si tratta di veri e propri protocolli per delineare procedure operative per la caratterizzazione delle Microzone Omogenee in Prospettiva Sismica (MOPS), la delimitazione delle Zone di Attenzione e la valutazione della Risposta Sismica Locale all'interno delle MOPS. In tal senso, si vuole sottolineare una volta di più il decisivo ruolo svolto dagli studi di microzonazione sismica quale strumento di mitigazione del rischio sismico, non solo nelle fasi post-evento, ma soprattutto nell'ambito di una lungimirante strategia di prevenzione che privilegi l'adozione di corrette scelte in sede di pianificazione e progettazione.

This work provides new insights on the use of a combined multidisciplinary approach for estimating trend and rates of valley incision in tectonically active mountainous landscape. To this aim, here we present the results of a combined analysis including stream terraces investigation, longitudinal profiles modelling and time-dependent, catchment-scale, geomorphometry obtained in the headwater sector of the Tronto River basin, located in the southern epicentral area of the 2016-2017 seismic sequence of Central Italy. The most relevant tectonic structures in the area are the Mt. Gorzano fault (south-eastern sector), the Sibillini Mts thrust (western sector) and the southern tip of the active Vettore fault, ie the seismogenic structure responsible forthe 2016 mainshock. Geomorphometric analysis and stream long-profiles modelling were performed using a 5 m-gridded DTM obtained starting from the altimetric dataset included in the 1:5,000 topographic maps available for the whole study area in vector format. Time-dependent catchment-scale R=Sr metrics and long-profile indices (SL and ) were computed respectively using the hydrological tool in ESRI® ArcGIS and the TopoToolbox working in Matlab®. Stream terraces dataset derives from field survey, integrated with the visual inspection of a DTM-derived hillshade map and aerial/satellite imagery interpretations. The combination of R=Sr time-dependent metrics and stream terraces analysis allows to infer the timing of the base level changes during upper Quaternary and the long-profiles modelling provided interesting results for better comprehending the effects of these changes on the fluvial system. The analysis here performed provided new data useful for better understanding the trend and rates of the valley deepening in the headwater sector of the Tronto River, to reconstruct basin-scale modifications such as stream captures and, more in general, resulted useful for better comprehending the morphoevolution of this tectonically active key area of the Apennines. Nonetheless, our study did not allow to unravel the role exerted by the single active tectonic structures in the present and past fluvial morphodynamics, because of the superimposed effects of large gravitational rock slope failures on the spatial pattern of long-profiles anomalies and local base level variations.

During the Mw 6.0 Amatrice earthquake, which struck Central Italy on the 24th August 2016, the accelerometric station IT.AMT, located at about 10km from the epicentre recorded the highest values of the ground motion (Peak Ground Acceleration of the east component reached 0.87 g). Was IT.AMT station affected also by local soil conditions? To understand the role played by the site effects in the ground motion observed at AMT, we performed a detailed geological - geotechnical characterization of the site. Then, numerical analyses of seismic site response were carried out using 2D approaches. In parallel, several analysis were also performed on seismic records, to infer empirical amplification functions, used to compare the results of the numerical simulations. This study was partially supported by the Italian Department of Civil Protection (DPC) of the Presidency of Council of Ministers. The INGV-CNR IGAG collaboration made possible the realization of this multidisciplinary study, which includes detailed seismological, geological and geophysical analyses.

A geological survey has been carried out in the area of Amatrice, the most damaged town after the 24 August 2016 event, to provide a basic reference for geophysical and geotechnical data useful for seismic response analyses and microzonation studies. The morphologies and the stratigraphic-structural setting of the investigated area are detailed on a 1:5000 scale geological map and cross sections, which derive from the integration of field-based observations and photo-geological interpretation. The Amatrice basin is filled by the one km-thick Laga Formation, composed of Messinian syn-orogenic marine sandstones and siltstones (Marini et al., 2015) and covered with disconformity by Quaternary conglomerates and sands, referred to alluvial fans, fluvial terraces and landslides. Presently, the Amatrice basin is a structurallycontrolled depression bounded eastward by the Gorzano Mt ridge, and westward by the Sibillini Mts thrust front (Koopman, 1983). Our observations focus on (i) relationships between geometry and extent of cover deposits, (ii) bedding of the substratum, and (iii) areal arrangement and distribution of the main fault systems. Amatrice is located on a N-S trending mesa bounded by steep escarpments. The siliciclastic substratum was folded by syn-orogenic movements, broadly forming a NW-SE-trending synform, and is dissected by two main fault systems of the Plio-Quaternary post-orogenic tectonics. The first system consists of N-S striking high angle normal fault segments, each one having continuous length of up to 2 km; the second consists of E-W-striking normal-to-strike slip fault systems dissecting the first one. N-S-striking faults are morphologically expressed by fault plane scarps and triangular facets, and control the areal distribution of the Quaternary fluvial deposits. These are up to 50 m thick below Amatrice and thin to few metres along the north west direction. East of Amatrice, the stratigraphic setting is dominated by SW-prograding alluvial fans, downlapping the substratum, while on the West the stratigraphic setting is strongly complicated by large scale deformations (folding and tectonic repetitions) produced by shortening mechanisms. The recognized morphological irregularities, stratigraphic heterogeneities, and structural alignments are considered critical elements to define, at local scale, subsoil models useful for evaluating seismic amplification effects.

Incised valleys and their fill represent important features of fluvial systems and can provide valuable information on external controls on sedimentation. Furthermore, the mode of stacking of multiple incised valleys may result in diverse connectivity of high permeability geobodies, which makes their origin and architecture important to understand for natural resources development. Based on dense borehole data and key outcrops along a 10 km-long transect, this study attempts at delineating the depositional architecture of a stacked multi-valley complex recording the Middle Pleistocene to Holocene evolution of the Tiber River system (Rome, Italy). Such a multi-valley complex is composed of four low rank/high frequency depositional sequences intercalated with pyroclastics, which fill in valley incisions entrenched into a substrate of Pliocene-Early Pleistocene marine clays. Owing to radiometric dating of pyroclastics, a robust correlation exists of valley incision and fill phases to odd and even Marine Isotopes Stages (MIS 14-1), which allows linking incised valley development to sea level changes. Located c. 20 km upstream from coeval shorelines, the investigated valleys have widths in the range of 0.5-2 Km and depth/thickness of up to 60 m and a recurrent tripartite pattern of their fills including: i) an up to 10 m thick and laterally extensive basal unit of dominantly gravelly-sandy deposits; ii) a middle unit (thickness in the range of 20-30 m) composed of vertically stacked sandy channel bodies (width in the range of 200-400 m) sided by floodplain muds; iii) a top unit composed of laterally stacked channel sands and, subordinately, floodplain muds, which result in extensive tabular sand bodies. Correlation to MIS suggests the fill of the studied incised valleys might reflect early deposition under low accommodation conditions within braided channel belts (lowstand and early transgressive phases) followed by deposition in sinuous channel belts (late transgressive and high-stand phases). In turn, successive incised valleys are stacked in an entrenching and westward shifting fashion, which is interpreted to reflect superimposition of regional uplift, topographic confinement from south-easterly sourced pyroclastics of the Albani Hills Volcanic District and glacio-eustasy. The resultant stratigraphic architecture of the Tiber multi-valley complex is such that high-permeability gravelly and sandy deposits are locally connected across successive valley fills. However, the studied example highlights how degree of connectivity of multiple incised valleys fills is ultimately controlled by external forcing factors (e.g. regional uplift and topographic confinement) superimposing to higher frequency changes of base level. It can be speculated that, by forcing lateral shifting of a fluvial stream, superimposition of differential uplift/subsidence to relative sea level changes more likely develops into less connected incised valley fills.

This work deals with the assessment of local seismic response in the explosive volcanic settings by reconstructing the subsoil model of the Stracciacappa maar (Sabatini Volcanic District, central Italy), whose pyroclastic succession records eruptive phases ended about 0.09 Ma ago. Heterogeneous characteristics of the Stracciacappa maar (stratification, structural setting, lithotypes, and thickness variation of depositional units) make it an ideal case history for understanding mechanisms and processes leading to modifications of amplitude-frequency-duration of seismic waves generated at earthquake sources and propagating through volcanic settings.

A review and correlation of borehole data, mostly from a recent survey of drilling in Rome (Palatino Hill and Fori Romani), and outcrops studies have allowed to reconstruct the stratigraphic architecture of the subsoil. Fluvial lithofacies of the ancient Tiber River system are recognized, which fill three high relief incised valleys of Middle Pleistocene age within of which well dated pyroclastites occur. These valleys constitute portions of the low rank/high frequency depositional sequences (PG4, PG5 and PG6) forming the Middle Pleistocene to Holocene composite/high rank Ponte Galeria Depositional Sequence (Milli et al., 2016). The latter represents the most recent stratigraphic unit of the Roman Basin. From a lithostratigraphic point of view the low rank sequences have a good correspondence with the Villa Glori, Fosso del Torrino and Quartaccio Synthems (Funiciello & Giordano, 2008) and are correlated to MIS 14-13, 12-11, 10-9 respectively. Valleys are elongated in N-S direction, and each of them has dimensions comparable to the tributaries valleys developing within the low rank Late Pleistocene-Holocene Tiber Depositional Sequence (Milli et al. in press): 1-2 km in width and up to 50 m in thickness. They are well entrenched into the substratum that is composed of Pliocene-Lower Pleistocene marine clay and Lower-Middle Pleistocene fluvial sediments and pyroclastites. The investigated valley segments are located some 20 km upstream from the coeval shorelines, nevertheless they show an internal stacking pattern of facies recording base level changes, in turn related to the Quaternary climatic and high frequency/amplitude sea level fluctuations. Each valley infill shows at the base a 10 m thick and laterally continuous body of amalgamated pebbles and sands forming a braided channel belt, deposited under low accommodation conditions and correlated with late lowstand and early transgressive phases. It follows a 20-30 m thick intermediate portion showing sandy-silty deposits attributed to sinuous channel belt, and laterally confined by muddy floodplain deposits, often rich in organic matter (transgressive phase). On the top, the channel sandy facies tend to widen and grade laterally to pedogenized floodplain mud. The three recognized incised valleys are organized into a compound-composite stack that records their progressive entrenchment and westward migration, in response to regional moderate uplift, to lateral supply from pyroclastic flows sourced by Colli Albani from SE, and to differential erodibility of the substratum.

This work presents the results from numerical analyses in the damaged area of Saletta hamlet (Amatrice municipality), aiming at discussing factors leading to the observed damages after the 24th August 2016 Mw 6.0 earthquake and the following aftershocks. The area of Saletta was in fact highly ravaged by the first earthquake and during the whole seismic sequence. Geological-technical detailed field investigations were combined with an Electrical Resistivity Tomography and several noise measurements for better evaluating the main geological-morphological variability over the study area. Following insights from the reconstructed geological setting, a continuous coring borehole was drilled and a down-hole test performed together with a passive 2D small array and an active 1D MASW measurement. All these data were used to obtain the subsoil model for the numerical analyses that were carried out using both 1D and 2D approaches, including linear and equivalent linear ones, aiming at evaluating site effects.

New stratigraphic constraints have been detailed for the Amatrice Basin, an intermountain morpho-structural depression of the central Apennines (Italy) hosting up to 60-m-thick Quaternary continental deposits. Through the results coming from a 1:5,000 scale field survey and from facies analyses, we documented the geometry, thickness, and extent of the post-orogenic continental deposits filling this basin. The Quaternary deposits form a complex architecture of purely aggradational and aggradational/degradational terraces with a dominant component of conglomerates and gravels, at the bottom, and subordinate sands, at the top. The Quaternary deposits overlie an up to 1-km-thick succession of flysch sediments that accumulated in the western Laga Basin during the Miocene syn-orogenic phases in central Apennines. The collected data are used to constrain the style and mechanisms of both syn-orogenic (i.e., subsidence and terrigenous sedimentation in foredeep environment) and post-orogenic (i.e., uplift, erosion, and continental sedimentation) phases documented for the central Apennines. In particular, the post-orogenic history of the Amatrice Basin, if compared with those of surrounding intermountain basins of the central Apennines, includes limited basin subsidence, reduced thickness of the post-orogenic covers and progressive deepening of the drainage network during the Quaternary. The results shed light on the source-to-sink history of the Amatrice Basin, which results from a long-lived interaction between regional-scale factors (climate changes, chain uplift, and extensional tectonic regime) that influenced the activity of the hydrodynamic pattern and the amount of intrabasinal sedimentation during the Quaternary.