Landslides are one of the most hazardous secondary effects of earthquakes due to the potential for large-scale damage and long-term alterations to landscapes. During the 2016-2017 seismic sequence in Central Italy, many earthquake-triggered landslides (EQTLs) affected the road network and mountain trails. In this study, a methodological approach for analysing EQTLs, based on data derived from Unmanned Aerial Vehicle (UAV) surveys, is shown. The approach is applied to investigate the geometric, structural, geomechanical, and kinematic features of the Foce rockslide, which is introduced in the back analysis. The investigation involved three main steps: (i) set up of UAV-based Virtual Outcrop Models (VOMs) of the slope, (ii) a geomechanical characterisation of the rock mass through the VOM interpretation and conventional field data, and (iii) 3D Limit Equilibrium (LE) slope stability analyses. This study highlights the potential of UAV surveys for providing valuable data for stability analyses, especially in emergency conditions such as in the aftermath of seismic events.

The definition of landslide hazard is a step-like procedure that encompasses the quantification of its spatial and temporal attributes, i.e., a reliable definition of landslide susceptibility and a detailed analysis of landslide recurrence. However, available information is often incomplete, fragmented and unsuitable for reliable quantitative analysis. Nevertheless, landslide hazard evaluation has a key role in the implementation of risk mitigation policies and an effort should be done to retrieve information and make it useful for this purpose. In this research, we go through this topic of optimising the information available in catalogues, starting from landslide inventory review and constitution of a boosted training dataset, propaedeutic for susceptibility analysis based on machine learning methods. The temporal recurrence of landslide events has been approached here either through the definitions of large-scale quantitative hazard descriptors or by analysis of historical rainfall (i.e., the main triggering factor for the considered shallow earth slope failures) databases through the definition of rainfall probability curves. Spatial and temporal attributes were integrated, selecting potential landslide source areas ranked in terms of hazard. Data integration was also pursued through persistent scatterer interferometry analysis which pointed out areas of interest within potential landslide source areas featured by ongoing ground movement. The consequential approach led to the definition of the first hazard product of the city of Rome at a local scale functional for advisory purposes or the statutory level, representing a thematic layer able to orient the risk managers and infrastructure stakeholders

Rainfall-induced landslides represent a major threat to human activities, and thus an improved understanding of their triggering mechanisms is needed. The paper reports some preliminary inferences on this topic, based on the data recorded over a 2-year period by a multi-parametric monitoring station located on one of the slopes of the Monterosso catchment (Cinque Terre, north-western Italy). This catchment has experienced multiple, concurrent shallow landslides after intense rainfall events. After defining a soil hydraulic model through data interpretation and numerical simulations, slope stability analyses were performed to elucidate several aspects related to shallow landslide occurrence. Both long-term climate conditions and single rainfall events were simulated via physically based approaches. The findings from these simulations enabled us to assume the pattern of infiltration and quantify the impact of soil hydraulic behavior on landslide triggering conditions. In this regard, various analyses were carried out on the same triggering event both at local scale and in the overall catchment, with a view to highlighting the role of initial soil moisture and soil hysteretic behavior in slope stability.

Over the last 2 decades, the topic of earthquaketriggered landslides (EQTLs) has shown increasing relevance in the scientific community. This interest is confirmed by the numerous articles published in international, peer-reviewed journals. In this work we present a database containing a selection of articles published on this topic from 1984 to 2021. The articles were selected through a systematic search on the Clarivate(TM) Web of Science(TM) Core Collection online platform and were catalogued into a web-based GIS (web-GIS), which was specifically designed to show different types of information. After a general analysis of the database, for each article the following aspects were identified: the bibliometric information (e.g. author(s), title, publication year), the relevant topic and sub-topic category (or categories), and the earthquake(s) addressed. The analysis allowed us to infer general information and statistics on EQTLs (e.g. relevant methodological approaches over time and in relation to the scale of investigation, most studied events), which can be useful to obtain a spatial distribution of the articles and a general overview of the topic.

This paper deals with the origin of the Pretare clastic deposit (PRA), which crops out along the Morricone fluvial valley in the Central Apennines of Italy. With the aim of deciphering the genesis of the PRA deposit, geological s.l. and geomorphological analyses were carried out allowing for the interpretation of the PRA deposit as a rock avalanche. Furthermore, geological cross sections constrained by well-log and field survey data, together with stratigraphic, sedimentologic, and morphometric analyses, allowed us to assign the deposit to a catastrophic rock slope failure, which occurred during a cold climate of the Late Pleistocene. Several issues concerning the propagation mechanisms were inferred from the mapping of 350 boulders over the entire accumulation area and from the measure of the morphometric parameters of the landslide body. We also performed a restoration of the potential source area by comparing the reconstructed pre- and post-failure DEMs. A missing volume of 8.41 106 m3 was estimated on the south-eastern side of the Vettore Mt., which is consistent with the deposit volume computed from the geological interpretation (10.56 106 m3). The outcomes of this study provide useful insights for a better understanding of the Quaternary morpho-evolution of the Central Apennines area where analogous rock avalanche events marked the recent evolution of the belt.

Obiettivo generale del lavoro è stato una prima definizione degli scenari di innesco per piogge intense e/o prolungate di frane in terra di prima generazione. Si tratta di una "prima definizione" in quanto, come di prassi quando si vogliono valutare soglie pluviometriche di innesco con finalità di nowcasting e warning, il processo si deve sviluppare tramite livelli di conoscenze ed affidabilità incrementali nel tempo; si parte quindi da una prima base informativa "sperimentale", basata come in questo caso su dati già disponibili (e minimali), che poi deve essere successivamente sviluppata ed integrata con informazioni maggiori in termini di numero e qualità e/o validata tramite l'osservazione di eventi futuri e la valutazione della rispondenza tra scenari previsti e scenari realmente accaduti.

In this work, we present the results of a rockfall trajectory study performed on the south-western slope of Mt. Catiello (Sorrento Peninsula, southern Italy). Such a study develops within a multi-methodological approach which integrates different types of remote sensing data and techniques. Specifically, ground-truth data (e.g., rock mass geo-structural information, rock block inventory) were generated by geologically-supervised interpretations of high-resolution virtual outcrop models (VOMs). These data were then used for reconstructing the in-situ fractured rock mass attributes of the Mt. Catiello peak, as provided by a Discrete Fracture Network (DFN) model, and to prepare the subsequent numerical simulations of rockfall trajectories. The resulting rockfall scenarios are consistent with the ground-truth data, both in terms of size and spatial distribution. Thus, we believe that the proposed approach can be effectively applied to other areas, characterized by similar geological features but higher levels of exposure and vulnerability.

Earthquake-induced landslides represent a significant seismic hazard since they can largely increase the damage and losses due to a seismic event, an issue that must be considered in land-use and risk management purposes. However, it can be difficult to consider all the natural variables, such as geotechnical parameters, that predispose the occurrence of landslides under a specific dynamic triggering, especially for wide areas. Among these, the most important and critical ones to quantify at large scale, are represented by the hydraulic conditions in both unsaturated and saturated media. For this reason, in this work we present a newly developed GIS tool that was specifically designed for the automation of a pseudo-dynamic Newmark model to estimate the co-seismic displacements over wide areas. The tool takes into account reactivations of landslides under different rupture mechanisms and parametrically weighs the role of variable initial soil moisture or pressure head conditions, as well as the influence of ground shaking resulting from local amplification effects. The proposed tool was tested in the Molise region (central-southern Italy), where almost 23,000 existing landslides have been selected for evaluating potential reactivations. The obtained results point out the importance of local conditions on the displacement amount, even by considering a unique return period of the seismic action. Strengths and weaknesses of the proposed model have been also highlighted in view of potential future applications in the framework of co-seismic landslide risk assessment and mitigation measures.

Archaeological areas in the mountain region of central Italy can be seriously threatened by geological hazards, and efforts are required to preserve cultural heritage. The Lucus Angitiae is a pre-Roman site located along the western edge of the Fucino Basin, the largest continental depression of central Apennines. The carbonate slope overhanging the area is affected by active rockfall processes from two main rock escarpments. In this paper, rockfall assessment was pursued through a 3D kinematic modelling, performed by adopting a probabilistic approach. Specific attention was dedicated to the choice and calibration of the input data, based on field evidence and a literature review. Two different sizes of wedge-shaped rock blocks were identified on rock escarpments, and specific stability analyses were performed. Sensitivity analyses accounting for possible triggering factors, such as water pressure increase and seismic action, were also carried out, together with an investigation of the seismological characteristics of the area. The results of the numerical simulations were used to design effective countermeasures in the framework of a mitigation plan for protection of the archaeological site. Finally, clues of gravity-driven slope deformations at the slope scale were documented, framing the rockfall process in a wider geological scenario.

A reliable subsoil model represents the first step in assessing potential geological hazards and adopting proper mitigation measures accordingly. However, one of the main difficulties related to the definition of such models concerns the extrapolation of single-point data over wide, uninvestigated areas. For this reason, in this work, we reconstruct a subsoil model within an alluvial basin through a methodology specifically based on spatialstatistical analyses of geophysical in situ point measurements. In particular, measurements of ambient noise were analysed and extrapolated to obtain a spatially continuous distribution of fundamental resonance frequency (f0) over the entire basin. Local portions of the basin were then defined according to a specific relationship between f0 and the minimum distance from the bedrock outcrops (MDBO). This analysis revealed how the position of the identified clusters is consistent with the asymmetric geometry of the basin. The resulting simplified subsoil model was then validated through additional experimental measurements of ambient noise to evaluate the reliability of the proposed methodology. As the test site, we selected the Firenze-Prato-Pistoia Basin (Tuscany region, central Italy), where more than two hundred homogeneously distributed noise measurements were collected from previous seismic microzonation investigations.

In the last two decades large clastic deposits in Central Apennines with specific morphological and sedimentological features have been interpreted as the result of Quaternary rock avalanche events (e.g., Di Luzio et al., 2004; Bianchi Fasani et al., 2014; Schilirò et al., 2019; Antonielli et al., 2020). The analysis of such deposits, that are located within intermontane basins and narrow valleys bounded by high mountain ridges, have improved the knowledge about this kind of massive rock slope failures, also clarifying their relationship with Deep-seated Gravitational Slope Deformations.The present study then describes a multidisciplinary analysis carried out on a huge rock block deposit which crops out within the Pretare-Piedilama Valley, in the piedmont junction area of the Sibillini Mountain range (Central Italy), where Mesozoic basinal carbonates overthrust Miocene foredeep deposits.Specifically, we performed sedimentological, stratigraphical and morphometric analyses on the clastic deposit; results support the interpretation of the event as a rock avalanche body. The accumulation area shows a T-like shape with a wide, E-W-oriented, proximal part and a N-S channelization in the central and lower sectors. The evidence suggests erosional events and tectonics as controlling factors on rock flow deposition. In this respect, the area was involved in the 2016 central Italy seismic sequence and was tectonically active during Quaternary times (Tortorici et al., 2009).As regards on the deposit genesis, considering the geometric characteristics of a sub-rectangular detachment area located on the southern edge of the Sibillini Range, an original mechanism of rockslide failure involving about 8·106m3 of Early Jurassic limestone was inferred. Here, the post-failure geomorphic features behind the main scarp are considered for the evaluation of hazard conditions.Finally, well-log analysis of the clastic sequence filling the Pretare-Piedilama Valley evidenced additional Quaternary landslide events occurred before the rock avalanche, thus testifying to a long history of large slope instabilities in the area controlling the landscape development.

In Norway, shallow landslides are generally triggered by intense rainfall and/or snowmelt events. However, the interaction of hydrometeorological processes (e.g., precipitation and snowmelt) acting at different time scales, and the local variations of the terrain conditions (e.g., thickness of the surficial cover) are complex and often unknown. With the aim of better defining the triggering conditions of shallow landslides at a regional scale we used the physically based model TRIGRS (Transient Rainfall Infiltration and Grid-based Regional Slope stability) in an area located in upper Gudbrandsdalen valley in South-Eastern Norway. We performed numerical simulations to reconstruct two scenarios that triggered many landslides in the study area on 10 June 2011 and 22 May 2013. A large part of the work was dedicated to the parameterization of the numerical model. The initial soil-hydraulic conditions and the spatial variation of the surficial cover thickness have been evaluated applying different methods. To fully evaluate the accuracy of the model, ROC (Receiver Operating Characteristic) curves have been obtained comparing the safety factor maps with the source areas in the two periods of analysis. The results of the numerical simulations show the high susceptibility of the study area to the occurrence of shallow landslides and emphasize the importance of a proper model calibration for improving the reliability.

In the last years, statistically based models (such as Logistic Regression) have been frequently used for evaluating the probability of landslide occurrence over large areas. In the case of Rome, over the years, more than 348 landslides have been recorded throughout the city. For this reason, in this study, we implemented and evaluated three main validation criteria of logistic regression to assess the rainfallinduced landslide susceptibility in a specific area of the city of Rome. Through the evaluation of the predictive performances, the best model has been identified and the results were also compared with those obtained in similar case studies.

In this paper we inferred the origin of a huge clastic deposit (i.e. L'Aquila Breccia) which widely crops out within the L'Aquila intermontane basin, a tectonic depression in central Apennines, that is bounded by seismogenic active faults, as demonstrated by the earthquake occurred on April 6, 2009 (Mw 6.1). The genesis of this deposit is still debated in the literature: for this reason, a number of methods have been applied, mainly aimed at evidencing its geomorphological and sedimentological features, as well as at defining its geometry and volume through cross sections constrained by borehole data and field observations. On the basis of the obtained results, we identified such deposit as resulting from a Quaternary rock avalanche event. In particular, the rock avalanche would have detached during the cold climate phases of late Middle Pleistocene from the southern slope of the Gran Sasso Range, a sector characterized by the presence of numerous DGSD-related landforms. We performed morphometric analyses of the Gran Sasso slope, in order to define the potential source area of the inferred rock avalanche and, according to the results, the volume estimated from this area (about 10 m) is coherent with the volume calculated for the preserved rock avalanche deposit. Furthermore, we analyzed the main features of the deposit (i.e. age and morphometric parameters) also in the light of similar rock avalanche events occurred in the same region during the Quaternary, with the aim of discussing potential analogues and better understanding the role of gravity-induced processes in the Quaternary morpho-evolution of the Apennine chain.

On 16 August 2018, a M 5.1 earthquake occurred in the Molise region (Central Italy) during an intense rainfall event which cumulated up to 140 mm in 3 days. Within 5 days after the seismic event, 88 landslides were surveyed and classified in disrupted and coherent as well as in first-time failures and reactivation. As it resulted by the inventorying, most of the surveyed ground effects were represented by coherent landslides involving clays, marly clays, and cover deposits on low dipping slopes. A spatial distribution analysis of landslides in relation to seismic action and rainfall intensity was carried out to evaluate the possible contribution of both the rainfall-induced saturation and the earthquake shaking to landslide triggering. Based on this analysis, in the epicentral area, it is not possible to clearly split the role of seismic and hydraulic destabilising actions, while, at greater distances, the joined contribution of rainfall and earthquake shaking could have promoted slope failures. Comparisons among collected data and existing worldwide catalogues allow to highlight, through the analysis of the spatial distribution of the surveyed landslides, the possible and not negligible effect of soil saturation during the seismic shaking both in epicentral distance vs. magnitude distribution and in number and spatial concentration of triggered ground effects.

Sedimentary structures within rock avalanche deposits have gained increasing attention in recent years, since they may provide useful information about the dynamics of such energetic events. This work then is aimed at better defining the physical processes arising during the propagation, paying particular attention to the kinetic sieving mechanism, and strengthening the assumption (widely diffused in the literature) that such a process does not occur for similar events. Specifically, after the examination of two rock avalanche deposits in Central Italy, where cuts through the fragmented deposits are accessible and illustrative of the sediment texture, a series of laboratory flume tests have been performed in order to investigate in detail the flowing process. A simplified physical model for granular agitation has been then introduced to explain how and why kinetic sieving may occur at the laboratory scale and, in the case of natural granular flows of reduced size, also at the field scale.

Hundreds of landslides were triggered by the mainshocks (up to Mw 6.5) that occurred in 2016 in Central Italy during the seismic sequence that originated in the Apennine and ended in January 2017. These landslides were studied via field-based investigation and remote sensing techniques during the weeks immediately after the mainshocks occurred. EarthQuake-triggered Landslides (EQtLs) mostly consisted of rockfalls and rockslides. The spatial distribution of the examined EQtLs with respect to the epicentres of the main shocks resulted in very good agreement with the available empirical curves of maximum distance vs. magnitude. Based on the collected dataset, approximately 70% of the landslides impacted transportation routes (national, provincial and secondary roads linking towns and mountain villages) since they principally detached from road cuts. The landslides caused traffic interruption, and some delayed rescue vehicles from reaching the zones most damaged by earthquakes; moreover, some landslides caused the temporary isolation of several localities in the epicentre area. Even if it seems obvious that road cuts favour slope failure under shaking conditions, the dataset reported here is the first one for Italy where such an effect is quantified. Moreover, a statistical analysis was conducted to explore the relationships between the spatial distribution of EQtLs and some selected causative factors, including both natural (i.e., earthquake and terrain) and anthropogenic factors (i.e., presence of roads and trackways). Among the considered combinations of causative factors (both natural and anthropogenic), this study demonstrates that the occurrence of the uphill road cuts at the bottom of deep incised V-shaped valleys strongly influenced the spatial clustering of the EQtL triggered in 2016 in Central Italy.

In the last years, the shallow landslide phenomenon has increasingly been investigated through physically based models, which try to extend over large-area simplified slope stability analyses using physical and mechanical parameters of the involved material. However, the parameterization of such models is usually challenging even at the slope scale, due to the numerous parameters involved in the failure mechanism. In particular, considering the scale of the phenomenon, the role of transient hydrology is essential. For this reason, in this work we present the outcome of different experimental tests conducted on a soil slope model with a sloping flume. The tested material was sampled on Monte Mario Hill (Rome, Central Italy), an area which has been frequently affected by rainfall-induced landslide events in the past. In this respect, we also performed a physically based numerical analysis at the field conditions, in order to evaluate the response of the terrain to a recent extreme rainfall event. The results of the flume tests show that, for the same material, two different triggering mechanisms (i.e., uprise of a temporary water table and advance of the wetting front) occur by varying the initial water content only. At the same time, the results of the numerical simulations indicate that clayey sand and lean clay are the soil types mostly influenced by the abovementioned rainfall event, since the initial moisture conditions enhance the formation of a wide wetting front within the soil profile.

In this work, we describe a comprehensive approach aimed at assessing the slope stability conditions of a tuff cliff located below the village of Sugano (Central Italy) starting from remote geomechanical analysis on high-resolution 3D point clouds collected by terrestrial laser scanner (TLS) surveys. Firstly, the identification of the main joint systems has been made through both manual and automatic analyses on the 3D slope model resulting from the surveys. Afterwards, the identified joint sets were considered to evaluate the slope stability conditions by attributing safety factor (SF) values to the typical rock blocks whose kinematic was proved as compatible with tests for toppling under two independent triggering conditions: hydrostatic water pressure within the joints and seismic action. The results from the remote investigation of the cliff slope provide geometrical information of the blocks more susceptible to instability and pointed out that limit equilibrium condition can be achieved for potential triggering scenarios in the whole outcropping slope.