Fluvial inverse modelling for inferring the timing of Quaternary uplift in the Simbruini range (Central Apennines, Italy)

The regional topography of the Central Apennines results from convergence between the African and Eurasian plates that led to the formation of a Neogene NE-verging imbricate fold and thrust belt. During the final stages of the orogenic deformations, the whole area was affected by strong uplift and by extensional faulting oriented along the main direction of the Apennine chain. In this framework, the landscape evolution in subaerial conditions started diachronically and is testified by the relicts of clastic deposit at different height from base levels of the present drainage network. In the Simbruini range, there are no absolute dating records neither of the most ancient clastic units deposited after the Messinian thrust-top facies nor of tectonic events. Trying to fill this gap, we used geomorphometric analyses to infer the timing of the recent phases of the tectonic history of the Simbruini range. Specifically, we identified the main non-lithological knickpoints along the river longitudinal profiles, clustered their altimetric distribution and correlated them with the levels of continental clastic deposits reserved at different elevations. Furthermore, we inferred the uplift history of the range by applying the inverse modelling of the river longitudinal profiles. Assuming a block uplift model, the drainage network cutting the Simbruini range recorded on average about 2.4 Myr of tectonic history, characterized by variable base level fall rates (corresponding to uplift rates). According the average tectonic history, the highest base level fall rate of 690 m My-1 was reached at 1.65 Ma, followed by the minimum of about 370 m My-1 , reached at 0.75 Ma, and by a second rise, up to a present-day value of 660 m My-1

Exploring the geomorphological adequacy of the landslide susceptibility maps: A test for different types of landslides in the Bidente river basin (northern Italy)

Landslide susceptibility modelling is a crucial tool for implementing effective strategies in landslide risk mitigation. A plethora of statistical methods is available for generating accurate prediction images; however, the reliability of these models in terms of geomorphological adequacy is often overlooked by scholars. This critical flaw may result in concealed prediction errors, undermining the trustworthiness of the obtained maps. A key aspect of evaluating the geomorphological soundness of these models lies in factor analysis, specifically considering the correlation of explanatory variables with the final susceptibility score rather than solely focusing on their impact on model accuracy. This study delves into research conducted in the Bidente river basin (Italy) that analyes results obtained from slide, flow, and complex susceptibility models using Weight of Evidence (WoE) and Multivariate Adaptive Regression Splines (MARS) statistical methods. The research critically examines each factor class's role in defining susceptibility scores for different landslide typologies. The comparison between susceptibility maps generated by WoE and MARS for each typology (slide = 0.78; flow = 0.85; complex: 0.79) (slide = 0.78; flow = 0.85; complex: 0.79)reveals good to excellent prediction skill, with MARS demonstrating a 5 % higher performance index. The study emphasises the importance of spatial relationships between variables and landslide occurrences, highlighting that individual classes of variables influence the final susceptibility score based on their combined role with other predictor classes. In particular, in this study, results highlight that lithotecnical and landform classification classes delimit the landslide domain, while topographic attributes (steepness, curvatures, SPI and TWI) modulate the score inside. The proposed approach offers insights into investigating the geomorphological adequacy of landslide prediction images, emphasising the significance of factor analysis in evaluating model reliability and uncovering potential errors in susceptibility maps

Geomorphic signature of segmented relief rejuvenation in the Sierra Morena, Betic forebulge, Spain

The foreland relief of alpine orogenic belts is often rejuvenated due to the intraplate propagation of orogenic deformation. Thus, in these long-lived areas, the localisation of relief rejuvenation may be largely controlled by the reactivation of previous mechanical discontinuities. In this regard, we explored the relationship between the relief rejuvenation pattern and the distribution, geometry, and kinematics of faults in a wide segment of the Betic foreland (Sierra Morena, southern Spain). Specifically, we focused on the forebulge, a WSW–ENE flexural relief that formed, paired to the Betic foreland basin, in response to orogenic load. For this purpose, we applied both qualitative and quantitative geomorphological tools, including geomorphic indices and knickpoint pattern modelling in χ space. We found that the pattern of relief rejuvenation responds to large-scale flexural uplift coupled with the tectonic activity of two groups of faults that often show evidence of reactivation, namely overall WSW–ENE faults contributing to both regional NNW–SSE relief segmentation and vertical extrusion of the forebulge, and NW–SE reverse faults associated with an outstanding WSW–ENE topographic segmentation in the west of the study area. In addition, our knickpoint modelling suggests that the faults related to the southernmost Sierra Morena mountain front have been particularly active in recent times, although their activity span and the relative uplift that they accommodate differ along the Sierra Morena/foreland basin limit. The knickpoint pattern also suggests a significant reorganisation of the analysed drainage basins. The strain partitioning accommodated by the structures involved in relief rejuvenation suggests the intraplate propagation of the transpressional deformation reported from the Betic external fold and thrust belt.</p

Time-dependent rock-mass deformations, geological aging and landscape evolution as predisposing factors for large rock landslide triggering

Le deformazioni di versante tempo-dipendenti sono solitamente connesse al processo Mass Rock Creep (MRC) che agisce su una grande scala spazio-temporale attraverso una variazione continua e non lineare dello stato tenso-deformativo di intere porzioni di versante. Inoltre è fortemente condizionato dalla tettonica e dall'evoluzione della rete di drenaggio. Infatti, sia il sollevamento che l'evoluzione morfologica permettono lo svincolo cinematico di porzioni di versante isolando un carapace di ammasso roccioso che inizia a deformarsi per processo di MRC fino al collasso. Il limite di questi schemi teorici è rappresentato dalla difficoltà di stimare con precisione il tempo di inizio del processo, discriminandone le diverse fasi, nonché di determinare la viscosità della matrice rocciosa, una delle componenti più importanti del sistema. A tal proposito, l'obiettivo generale della mia ricerca è quello di isolare il contributo del geological aging (inteso come evoluzione temporale delle morfostrutture in direzione della propagazione dell'orogene), e dell'evoluzione del paesaggio nello sviluppo di deformazioni tempo-dipendenti da MRC. Tuttavia, l'obiettivo specifico è quello di dimostrare le relazioni tra i suddetti fattori attraverso un test metodologico lungo un transetto orientato parallelamente alla direzione delle morfostrutture in Lorestan, nei Monti Zagros (Iran) da NE a SW. Sulla base dei vincoli temporali alla ricostruzione morfo-evolutiva ottenuta per 3 casi di studio, è stato implementato un Landscape Evolution Modeling (LEM) al fine di calibrare il modello mediante back-analysis individuando l'esatto step temporale in cui la soglia morfoevolutiva critica è stata raggiunta che ha originato il processo MRC responsabile di deformazioni non elastiche all'interno dell'ammasso roccioso coinvolto. Il calcolo della strain rate, e poi successivamente del displacement rate, è stato eseguito, dapprima, sui profili di frana reali per valutare il possibile range di valori di strain rate nei casi studio attraverso un'analisi di sensitività sul parametro di viscosità. Successivamente, è stato implementato anche nei LEM per definire la cronologia di deformazione legata al processo MRC dei pendii simulati. Posso concludere che il LEM, vincolato temporalmente dall'analisi morfo-evolutiva, consente di ricostruire la storia del creep dei sistemi di versante-valle. L'approccio multi-modellistico presentato sarà continuato dalla modellizzazione numerica tenso-deformativa per calibrare la reologia dell'ammasso roccioso mediante ulteriori analisi che consentano di valutare un rischio dipendente dal tempo oltre che dallo spazio.The slope time-dependent deformations are usually related to the Mass Rock Creep (MRC) process that acts on a large time-space scale through a continuous and non-linear variation of the tensile-deformational state of entire portions of slopes. It is also strongly conditioned by the tectonics and the evolution of the drainage network. Indeed, both uplift and the morpho-evolution kinetically release portions of slopes isolating a rock mass carapace that starts to deform by the MRC process until collapse. The limit of these theoretical schemes is represented by the difficulty of estimating accurately the starting time of the process, discriminating the distinct phases, as well as determining the viscosity of the rocky matrix, one of the most important components in the system. In this regard, the general objective of my research is to isolate the contribution of geological aging (intended as the time-evolution of morpho-structures in the direction of propagation of the orogen from the hinterland to the foreland), and of landscape evolution in the development of MRC-driven time-dependent deformations. However, the specific objective is to demonstrate the relationships among the aforementioned factors through a methodological test along a transept oriented parallel to the direction of the morpho-structures in Lorestan, in the Zagros Mountains (Iran) from NE (older geological age) to SW (younger geological age). Based on the time constraints to the pre-failure morpho-evolutionary reconstruction provided in 3 case studies, a Landscape Evolution Modelling (LEM) was implemented in order to calibrate the model by back-analysis individuating the exact temporal step in which a critical morpho-evolutive condition was reached originating the MRC process responsible for unelastic strains within the involved rock mass. The strain rate computation, and then subsequently the displacement rate, was performed, first, on the real landslide profiles to evaluate the possible strain rate value range in the case studies through a sensitivity analysis on the viscosity parameter. After that, it was also implemented in the LEMs to define the deformation history linked to the MRC process of the simulated slopes. I can conclude that the landscape evolution modelling, temporally constrained by the morpho-evolutionary analysis, allows reconstructing the creep history of slope-valley systems. The presented multi-modelling approach will be continued by the stress-strain numerical modelling to calibrate the rock mass rheology by further back analysis allowing assessing a time-dependent risk

Evaluation of tectonics and landscape evolution contribute as predisposing factor for a Mass Rock Creep deforming slope in the Zagros Belt (Iran)

In the hillslope landscapes of tectonically active regions, the steep topography represents the most evident result of rock uplift, valley incision and landslide erosion. In response to rock uplift, relief and hillslope dip increase linearly in time mainly due to fluvial erosion processes in landscapes affected by low to moderate tectonic forcing. Nonetheless, such a linear increase in relief and hillslope dip is limited by the reaching of threshold slope conditions associated with the hillslope material strength, until the latter is exceeded by gravitational stress giving rise to bedrock landslides. In this regard, Mass Rock Creep (MRC) process may become a primary factor for damaging rock masses so leading to slope failures that generate huge rock avalanches. MRC acts on large time-space scale through a continuous and non-linear variation of stress-strain conditions of entire portions of slopes and the coupled role of tectonics and landscape evolution represents a predisposing factor for Deep Seated Gravitational Slope Deformations (DSGSD). This research focused on the Loumar DSGSD that affects the NE slope of the Palganeh anticline in the Lorestan region (Zagros Mts., Iran), almost 90 km northwest of the Seymareh landslide which is more famous as it represents the largest landslide on Earth surface. The Loumar DSGSD evolution is strictly related to the vertical and lateral growth of the fold and to the evolution of the Seymareh river drainage system that kinematically released the slope at the bottom likely causing the initiation of the deformational process. We combined an inverse modelling of the river profiles linked to the fold uplift history and the analysis of a plano-altimetric distribution of geomorphic markers, correlated to the detectable knickpoints along the river longitudinal profiles, which allowed to constrain the main morpho-evolutionary stages of the valley. These data will be used to constrain a Landscape Evolution Model (LEM) and a stress-strain numerical model, to be performed under time-dependent creep conditions, that will be calibrated by a back analysing the slope evolution from the LEM. The final goal will be to discuss the possible role of impulsive triggers (earthquakes) in anticipating the time-to-failure of the MRC deformational process

New insights on the emplacement kinematics of the Seymareh Landslide (Zagros Mts., Iran) through a novel spatial statistical approach

The giant prehistoric Seymareh landslide in the Zagros Mountains (Iran) is one of the largest known landslides on the Earth’s surface. The debris with an estimated volume of 44 km3 dammed two rivers, generating three lakes, that persisted for about 3 ka after the event. The post-overflow morphodynamics, characterized by an accelerated and intense stream network erosion, obliterated most of the primary landforms, such as ridges and blocks on the debris surface, making it difficult for scientists to interpret the emplacement kinematics of the landslide. In this regard, a novel spatial statistical approach is proposed here to zone the landslide debris in primary (original) and secondary (modified) regions which are, respectively, attributed to the original shape of the landslide debris and the one reshaped by fluvial erosion. The zonal computation combines the density classes of the mapped primary (ridge and blocks) and secondary (gullies) landforms, according to assumed conditions for representativeness of primary and secondary zones. For validating the model, 62 soil samples taken from the debris surface were classified according to the Unified Soil Classification System standard, and the field density measurements were performed in 28 sites. Based on the classification results, six types of soils were detected, among which 68% of them were ML. The ML samples were aggregated into five subgroups based on their relative proximity, and for each subgroup, four permeability tests were performed. The permeability results demonstrate that the high permeability values are associated with secondary zones, while low values with primary ones, thus confirming the zonation proposed by the statistical approach. The study of the spatial arrangement of the kinematic evidence on the primary landforms allowed to deduce that the landslide was a double-step single event, which infilled a paleo-valley enclosed by two anticline folds. During the emplacement, a part of the debris dissipated its energy over passing the anticlines with divergent directions, NW and NE, while the rest swept back into the Seymareh paleo-valley into the SE direction. The proposed approach represents a promising tool for the detection of primary landforms to assess the emplacement kinematics of landslides

Emplacement kinematics of the Seymareh rock-avalanche debris (Iran) inferred by field and remote surveying

Comprendere la cinematica delle frane ed i loro meccanismi di rottura è essenziale per la definizione della pericolosità e per la ricostruzione di scenari di rischio funzionali a strategie di mitigazione. Le frane nel sud-ovest dell'Iran sono particolarmente numerose, specialmente nei bacini sedimentari degli Zagros. Secondo alcune stime basate su studi e ricerche fino ad oggi condotte,tra 10000 e 11000 anni fa, una grande frana (volume massimo stimato di 44 Gm3) è avvenuta nella città di Pol-e-Dokhtar, nella regione del Lorestan (settore ovest dell'Iran). Poiché questa frana ha sbarrato il corso del fiume Seymareh, è nota come la frana di Seymareh. Questa giga-frana è ritenuta la più grande sulla superficie terrestre. Nel presente studio, per la comprensione della cinematica di messa in posto della frana Seymareh, sono stati rilevati con elevato dettaglio elementi morfologici visibili sull'enorme accumulo di frana che si estende per circa 24.5 km in larghezza e per circa 19 km in lunghezza. Tra gli elementi morfologici rilevati vi sono dorsali di compressione e cumuli di blocchi, che sono stati identificati e cartografati integrando un rilevamento da remoto con un rilevamento di terreno. A seguire, sono state misurate la curvatura e la direzione delle dorsali e le dimensioni principali dei blocchi avvalendosi anche del GIS. Le direzioni delle dorsali su un detrito di frana possono rappresentare indizi morfologici della cinematica relativa alla sua messa in posto; nel caso della Seymareh le direzioni prevalenti sono risultate essere NW-SE e NE-SW. Nel corso di una specifica campagna, sono stati, inoltre, prelevati campioni di terreno, rappresentativi della matrice del detrito di frana, in punti diversi dell’accumulo, per poterli caratterizzare in laboratorio e classificare secondo lo standard USCS. I risultati della classificazione di laboratorio effettuata sulla matrice campionata nell'accumulo della frana Seymareh, mostrano che, per - la maggior parte, essa è rappresentata da terreni limosi a bassa compressibilità (di tipo ML secondo la classificazione USCS) mentre una parte più ridotta è rappresentata da terreni ghiaioso-argillosi e ghiaioso-limosi (di tipo GC e GM secondo la classificazione USCS) . Per ciò che attiene la distribuzione di queste matrici nel detrito, i terreni GC e GM sono stati campionati perlopiù in prossimità della zona di distacco della frana mentre i terreni ML sono stati prevalentemente campionati nelle posizioni intermedia e distale. La distribuzione di termini siltosi ed a grana grossa sono ascrivibili dalla Formazione di Asmari e la loro presenza nelle porzioni media e distale dell'accumulo di frana suggerisce che, già nelle fasi iniziali della messa in posto dell'accumulo di frana, il calcare della -Formazione di Asmari, che costituiva un'unica placca rigida originariamente a franapoggio sul versante dal quale si è distaccata la frana Seymareh, avrebbe raggiunto una minore distanza rispetto ai detriti generatisi dalle sottostanti formazioni a componente prevalentemente marnoso-argillosa (tra cui le Formazioni di Pabdeh-Gurpi). Ciò può essere giustificato anche alla luce della trappola sedimentaria rappresentata dalla paleo valle del Seymareh che avrebbe favorito l'accumulo dei primi detriti giunti, ascrivibili alla Formazione di Asmari. I detriti più fini si sarebbero, invece, accumulati in zona più distale rispetto all'area di distacco della frana muovendosi al di sopra della prima parte di deposito che aveva già colmato la paleo valle. La distribuzione e l'orientazione degli indicatori cinematici rilevati sul detrito di frana come anche la distribuzione dei terreni di cui esso è costituito portano, dunque, a confermare quanto già evidenziato da precedenti studi (Harrison e Falcon 1938, Roberts ed Evans 2013), ossia che la frana di Seymareh può essere considerata una rock avalanche verificatasi in un singolo evento. Inoltre, i risultati preliminari della distribuzione dei blocchi ed alcuni affioramenti della Formazione di Gachsaran osservati durante i rilevamenti sul campo hanno portato al riconoscimento della superficie basale dei detriti di frana rendendo possibile avanzare alcune ipotesi sulla morfologia sepolta della paleo valle del fiume Seymareh.Understanding the kinematics of landslides helps us to better constrain failure mechanisms and it is useful to define hazard and consequent risk scenarios for mitigation strategies. According to the literature, between 10 and 11 ka, a huge landslide (up to 44 Gm3) occurred close to the Pol-e-Dokhtar city in the Lorestan region (west of Iran). As this landslide blocked the Seymareh River, it is known as Seymareh landslide. Seymareh giant landslide is the largest landslide documented on the Earth surface and is of great interest for earth scientists. We deepened the analysis of the emplacement kinematics of this enormous landslide, using remote and field surveying. The boundary of landslide debris, the ridges, gullies and clusters of blocks inside the debris area were recognized and then ridges curvature and direction and major block dimensions were measured also using GIS tools. Ridges directions inside the landslide debris preliminarily suggest the kinematics of the mass mobility. Furtheremore, soil samples were took from matrix of landslide debris at different places inside the rock avalanche debris area for their classification according to the USCS standard. The results of grain size analysis on the matrix of the soil samples in combination with Atterberg limits in different regions of the debris show that the most of the matrix is represented by ML while a more reduced part is represented by GC and GM soils. GC and GM soils were mainly distributed closer to the detachment zone of the Seymareh landslide, while ML soils are mainly distributed in middle and distal positions. The preliminary results of block distribution and some outcrops of Gachsaran Formation observed during field surveys led to recognition of the landslide debris basal contact that helped us to speculate on the paleo-valley hidden morphology

Geomorphological investigation on the Siah-kuh Mass Rock Creep deformation (Zagros Mts., Iran) through Space-borne Synthetic Aperture Radar (SAR) interferometry and quantitative geomorphic analysis

The Siah-kuh Deep Seated Gravitational Slope Deformation (DSGSD) affected the SE slope of the homonym anticline in its SE periclinal closure in the Ilam region, only 30 km south of the Seymareh landslide, defined as the largest landslide on Earth surface (Zagros Mts., Iran). The deformation is driven by Mass Rock Creep (MRC) process and covers an area of about 6 km2. The evolution of the gravitational instability is closely connected to the drainage evolution of Dowairij River, since its erosion produced the stress kinematic release at the base of the slope likely starting the deformation process. Such instability is still active, and it has not been evidenced by the scientific community. The geomorphological study of the area was carried out firstly through the analysis and interpretation of remote data (Google Earth satellite optical images), which led to the first detection of possible gravity induced landforms, such as evidences of bulges and lateral releases within the deformed area of the Siah-kuh fold. To confirm the existence of ground displacement due to landsliding, InSAR techniques and quantitative geomorphic analysis were applied to the area. On one hand, we produced a surface velocity map and displacement time series in the Siah-kuh slope and surrounding areas by processing 147 radar images of the Sentinel-1 (A and B) satellite on ascending orbit from 17 October 2014 to 31 March 2019. The software SARscape (ENVI) was used to process the images and measure the surface displacements. On the other hand, a quantitative morphometric evaluation was also performed through the Tu index, to predict the catchment-scale suspended sediment yield on the deformation area produced by the Dowairij River system. We derived the erosion rate of the drainage network, responsible of the kinematic release of the slope and then, the time at which the MRC process could have started

Reconstruction of river valley evolution before and after the emplacement of the giant Seymareh rock avalanche (Zagros Mts., Iran)

The Seymareh landslide, detached ∼10 ka from the northeastern flank of the Kabir-kuh fold (Zagros Mts., Iran), is recognized worldwide as the largest rock slope failure (44 Gm3) ever recorded on the exposed Earth surface. Detailed studies have been performed that have described the landslide mechanism and different scenarios have been proposed for explaining the induced landscape changes. The purpose of this study is to provide still missing time constraints on the evolution of the Seymareh River valley, before and after the emplacement of the Seymareh landslide, to highlight the role of geomorphic processes both as predisposing factors and as response to the landslide debris emplacement. We used optically stimulated luminescence (OSL) to date lacustrine and fluvial terrace sediments, whose plano-altimetric distribution has been correlated to the detectable knickpoints along the Seymareh River longitudinal profile, allowing the reconstruction of the evolutionary model of the fluvial valley. We infer that the knickpoint migration along the main river and the erosion wave propagation upstream through the whole drainage network caused the stress release and the ultimate failure of the rock mass involved in the landslide. We estimated that the stress release activated a mass rock creep (MRC) process with gravity-driven deformation processes occurring over an elapsed time-to-failure value on the order of 102 kyr. We estimated also that the Seymareh damming lake persisted for ∼3500 years before starting to empty ∼6.6 ka due to lake overflow. A sedimentation rate of 10 mm yr−1 was estimated for the lacustrine deposits, which increased up to 17 mm yr−1 during the early stage of lake emptying due to the increased sediment yield from the lake tributaries. We calculated an erosion rate of 1.8 cm yr−1 since the initiation of dam breaching by the Seymareh River, which propagated through the drainage system up to the landslide source area. The evolutionary model of the Seymareh River valley can provide the necessary constraints for future stress–strain numerical modeling of the landslide slope to reproduce the MRC and demonstrate the possible role of seismic triggering in prematurely terminating the creep-controlled time-to-failure pathway for such an extremely large case study

Tectonic deformation and landscape evolution inducing mass rock creep driven landslides. The Loumar case-study (Zagros Fold and Thrust Belt, Iran)

Several landscape evolution models have been proposed so far to explain the dynamic feedback between Earth surface processes and tectonics in the Zagros Mountains. Nevertheless, the relationship among time-dependent rock mass deformations, landscape evolution rates, and tectonics in triggering large rock landslides is still poorly studied in this region and worldwide. To fill this gap, here we focus on the previously unknown Loumar landslide affecting the NE flank of the Gavar anticline (Zagros Mountains) through a multi-perspective methodology which includes SAR Interferometry, geomorphometry, linear temporal inversion of river profiles and field survey for independent OSL dating of geomorphic markers of landscape evolution. We estimated that at 93 +21/−16 ka the backlimb of the Gavar fault-propagation fold reached limit equilibrium conditions for the slope failure, caused by an acceleration in the fold growth. The growth of a minor fold also induced the abandonment of a meandering canyon and the river migration to a new narrow gorge. The fluvial downcutting kinetically released the limestone strata that started to deform through Mass Rock Creep (MRC). The MRC process accumulated inelastic strain until 5.52 ± 0.36 ka, when the slope evolved into a failure causing the partial occlusion of the valley and the generation of a pond. The obtained creep timespan of 104–105 years since the initiation of the MRC process is consistent with the typical lifespan of gravity-induced slope deformations in non-glaciated regions. For this reason, such an approach can be used for the reconstruction of slow deforming slope evolution to predict the hazard of slopes prone to massive rock slope failure, linking it to the MRC stages