Search

This work is focused on the study of recurrent debris flow events on the north-facing mountain slope of the Bulgheria massif (Cilento Unesco Geopark, southern Italy). These phenomena pose a threat for at least two villages and infrastructures on the lower slope. The main morpho-structure of the mountain slope is strongly controlled by the tectonic overlapping in form of multiple thrust-folding of the Meso-Cenozoic limestone related to the inner margin of the Apennine Carbonate Platform over lower-middle Miocene marly-clay flysch and previously overthrusted basinal units ranging from upper Oligocene to lower Miocene. Therefore, the mountain slope is sculpted by erosional deep incided ravines and sub-structural interfluve cliffed slopes passing downslope to depositional piedmont by evident and abrupt knick-point. Channels along the slope are periodically filled both through rock fall deposits occurring on channel's flanks and by soil creep and sheet wash phenomena at channel's heads, which supply new material for future flows. Such relationship between infilling rock fall phenomena and debris flows represents an interesting case study of interaction among different and concurrent landslide types providing an optimal example of space-time evolving landslide system. Landslide classes have been stored and mapped using a previously proposed object-oriented and event-based model and producing in this way a multi-temporal database. Landslide objects have been grouped into landslide subclasses using the latest landslide classification available. In the next step, a hierarchical classification has been applied, introducing two levels of aggregation and one level of decomposition. Landslide complexes group landslide objects of the same class sharing spatial connection, defining rock fall complex objects and granular soil wet flow complex objects. Landslide systems group all the interacting landslides, regardless of their type. Landslide components describe the various portions of a single landslide object. Every stored object has its temporal attributes distinguishing between time points (events) and time intervals (time frames). The integration of complex spatial relations through topological analysis and temporal characterization of data allows to build a flexible database structure adaptable to several specific needs and different outputs, such as basic landslide maps or event maps, multi-temporal and frequency analyses, or the study of the interactions among different types of landslide hazards. In this framework, a neologism could be introduced in landslide studies, as landslide eventory mapping, as a challenge for future applications. [ABSTRACT FROM AUTHOR]

Landslide susceptibility analysis based on the assessment of a quantitative relationship between multiple controlling factors and landslide occurrence is a consolidated approach for land-use planning in risk mitigation. The Zagros Mountain range (Iran) is one of the most spectacular examples of a landscape whose evolution has been controlled by the erosion of rock outcrops and the growth of thrust-fold structures (predisposing factors for gravity-driven deformations). This paper covers a preliminary study on the landslide susceptibility of the Lorestan region of the Zagros Mountains. Use was made of a bivariate Frequency Ratio, computed on a 30 m pixel size Shuttle Radar Topography Mission Digital Elevation Model. In particular, reliance was made on an unpublished inventory of landslides in the Lorestan Arc. Landslide susceptibility was assessed in the "Falls" (323) and "Slides" (297) categories, the numbers of which (unlike those of other categories) were regarded as suitable for robust modelling. A multi-parametric analysis was carried out to determine the susceptibility of each type of landslide to a set of contributing factors. These factors, most of which are commonly used in the literature, can be grouped in two main categories: a) static, including morphological, hydraulic, and geological factors, and b) pseudo-dynamic, including distance from active faults and steepness index (ksn), a morphometric tectonic uplift proxy computed along stream networks. The latter were considered as potentially landslide-triggering factors in the medium-long term, combining both the effects of transient tectonic forces of individual seismic events and morphotectonic effects on the slope-valley system. The statistical significance of these pseudo-dynamic factors was initially demonstrated via a univariate logistic regression with a randomly generated set of "stable" and "unstable" points. Then, models were built, and the importance of each conditioning factor was assessed by calculating the contribution of the factors in determining the mean landslide susceptibility index value in actual landslides, and the percentage of landslide cases in which the frequency ratio relative to each variable was above 1. With regard to the "Falls" category, the model showed (with a high reliability) that susceptible areas were those with a slope angle greater than 38°, associated with a 5000 m radius relief energy of about 1100-1550 m and a median fault distance of about 10 km. Conversely, the susceptibility model obtained for the "Slides" category showed that highly susceptible areas were those with slope angle values of 18°-35° and featuring outcrops of the most resistant lithotypes, such as limestone and marly limestone, especially close to flatiron landforms. The resulting model accuracy (validated with the prediction rate curve method on a sample dataset not used in the susceptibility analysis), was equal to 0.94 for "Falls" and 0.77 for "Slides", indicating a good prediction accuracy. [ABSTRACT FROM AUTHOR]

Seismic response studies carried out in the Municipality of Forio on Ischia (NA), southern Italy, following the 21st August 2017 earthquake allowed to detect local effects related to specific geological-structural settings that reflect the complexity of the volcanic context which characterises the entire island of Ischia and, more specifically, the western sector of Mt. Epomeo and the adjacent coastal plain of Forio. In particular, the following features have been observed: i) polarization and amplification effects in the proximity of tectonic elements that dissect the Zaro promontory, where volcanic deposits from massive to stratified widely outcrop; ii) stratigraphic resonances on significantly variable frequency values, changing within distances of a few hundred meters, which can be related to the juxtaposition of landslide debris (such as debris-/rockavalanches and lahar) in correspondence with the town of Forio; iii) seismic amplification in the sector involved in the ongoing gravitational deformation of Mt. Nuovo even in the absence of polarization of the particle motion. The peculiarities of the geological contexts analysed in the Forio Municipality allow to apply different interpretative schemes that vary from stratigraphic resonance (one-dimensional model of resonant column) mostly controlled by thickness and wave velocity in soft soils onto a stiff bedrock, to the resonance of jointed rock masses which are not completely released from the adjacent bedrock so avoiding typical free vibrations with normal modes (three-dimensional oscillating mass model), or to the interaction in the near surface with physical discontinuities responsible for modifying the physical properties of surface waves polarizing and amplifying them. The collected evidence of local seismic response in Forio exemplifies how not conventional interpretative keys for seismic zoning can be proposed to identify sectors whose response schemes do not necessarily fall within the standard of stratigraphic or topographical amplification adopted by current national guidelines for Seismic Microzonation (SM) studies. In particular, the evidence of local seismic response collected for the Forio Municipality were taken into account in the SM and relative products that were realised in the following years. [ABSTRACT FROM AUTHOR]

Copyright of Italian Journal of Engineering Geology & Environment is the property of Sapienza Universita di Roma and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Volcanic islands commonly testify the strict relation between volcano-tectonic activity and slope instability as very recently testified by the flank collapse of the Anak Krakatau active volcano which induced the destructive tsunami on 23 December 2018. The island of Ischia (Italy), which is part of the Phlegrean Volcanic District, has experienced since the Holocene several slope scale instabilities (i.e. debris- and rock avalanches). The latter occurred as direct consequence or feedback of a rapid caldera resurgence and associated seismicity and/or renewal of hydrothermal and magmatic systems. An ongoing slope-scale gravitational deformation process still affects large volumes of a thick greenish alkali-trachytic tuff sequence (the Mt. Epomeo Green Tuff - MEGT -) cropping out on the western flank of Mt. Epomeo (Mt. Nuovo), that represents the remnant of the caldera's most uplifted sector. The rock mass affected by ongoing deformation mobilized along a structurally controlled biplanar compound shear zone.In order to assess the relations and the possible interactions between the ongoing gravitational deformation and the hydrothermal system beneath the island, thermal and thermo-mechanical models of deep geothermal and slope systems were respectively reconstructed. Based on available geomechanical and petrophysical characterization under relevant temperature and pressure conditions, as well as on literature wells' geothermal profiles, a 2D thermo-mechanical model of the Mt. Nuovo slope was designed. A numerical model was computed along a section crossing the Mt. Nuovo slope, where ongoing deformation is testified by geomorphic evidence. The model was validated adopting an uncoupled thermal and mechanical numerical solution, back-analyzing the ongoing slope-scale gravitational process.The outcomes highlight the main role of Mass Rock Creep (MRC) in the onset of the slope instability, suggesting the interactions with the geothermal field in modifying the stress-strain response of the slope, which is able to alter its short- and long-term gravitational equilibrium.Thermo-baric field induced by hydrothermal rejuvenation can interact with the slope equilibrium causing the mechanical weakening of the compactant (i.e. ductile) MEGT tuff as consequence of transient exposure to high thermal perturbations, therefore increasing the rate of slope deformation. The thermo-mechanical numerical models, once constrained by geomorphic evidence and monitoring data, can be adopted for defining future scenarios (i.e. forward modelling) resulting by variation of physical conditions and/or mechanical parameters of the rock masses involved in the gravity-induced slope deformations. Through these forward analyses is possible to depict the worst physical conditions leading to ultimate paroxysmal events consisting in a generalised and catastrophic slope failure. [ABSTRACT FROM AUTHOR]

Central Iran provides an ideal region in which to study the long-term morphotectonic response to the nucleation and propagation of intraplate faulting. In this study, a multidisciplinary approach that integrates structural and stratigraphic field investigations with apatite (U + Th)/He (AHe) thermochronometry is used to reconstruct the spatio-temporal evolution of the Kuh-e-Faghan Fault in northeastern central Iran. The Kuh-e-Faghan Fault is a narrow, ~80-km-long, deformation zone that consists of three main broadly left-stepping, E-W--trending, dextral fault strands that cut through the Mesozoic--Paleozoic substratum and the Neogene--Quaternary sedimentary cover. The AHe thermochronometry results indicate that the intrafault blocks along the Kuh-e-Faghan Fault experienced two major episodes of fault-related exhumation at ca. 18 Ma and ca. 4 Ma. The ca. 18 Ma faulting/exhumation episode is chiefly recorded by the structure and depositional architecture of the Neogene deposits along the Kuh-e-Faghan Fault. A source-to-sink scenario can be reconstructed for this time frame, where topographic growth caused the synchronous erosion/exhumation of the pre-Neogene units and deposition of the eroded material in the surrounding fault-bounded continental depocenters. Successively, the Kuh-e-Faghan Fault gradually entered a period of relative tectonic quiescence and, probably, of regional subsidence, during which a thick pile of fine-grained onlapping sediments was deposited. This may have caused resetting of the He ages of apatite in the pre-Neogene and the basal Neogene successions. The ca. 4 Ma faulting episode caused the final exhumation of the fault system, resulting in the current fault zone and topography. The two fault-related exhumation episodes it with regional early Miocene collision-enhanced uplift/exhumation, and the late Miocene--early Pliocene widespread tectonic reorganization of the Iranian Plateau. The reconstructed long-term, spatially and temporally punctuated fault system evolution in intraplate central Iran during Neogene--Quaternary times may reflect states of far-field stress changes at the collisional boundaries. [ABSTRACT FROM AUTHOR]