Matano, Fabio

The utility of new imaging technologies to better understand hazardous geological environments cannot be overstated. The combined use of unmanned aerial vehicles (UAV) and digital photogrammetry (DP) represents a rapidly evolving technique that permits geoscientists to obtain detailed spatial data. This can aid in rapid mapping and analyses of dynamic processes that are modifying contemporary landscapes, particularly through the creation of a time series of digital data to help monitor the geomorphological evolution of volcanic structures. Our study comprises a short-term (in geological terms) monitoring program of the dynamic and diffuse Pisciarelli degassing structure caused by the interplay between intensive rainfall and hydrothermal activity. This area, an unstable fumarole field located several hundred meters east of the Solfatara Crater of the Campi Flegrei caldera (southern Italy), is characterized by consistent soil degassing, fluid emission from ephemeral vents, and hot mud pools. This degassing activity is episodically accompanied by seismic swarms and macroscopic morphology changes such as the appearance of vigorously degassing vents, collapsing landslides, and bubbling mud. In late-2019 and 2020, we performed repeated photogrammetric UAV surveys using the Structure from Motion (SfM) technique. This approach allowed us to create dense 3D point clouds and digital orthophotos spanning one year of surveys. The results highlight the benefits of photogrammetry data using UAV for the accurate remote monitoring and mapping of active volcanoes and craters in harsh and dangerous environments.

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Along the coastline of the Phlegraean Fields volcanic district, near Naples (Italy), severe retreat processes affect a large part of the coastal cliffs, mainly made of fractured volcanic tuff and pyroclastic deposits. Progressive fracturing and deformation of rocks can lead to hazardous sudden slope failures on coastal cliffs. Among the triggering mechanisms, the most relevant are related to meteorological factors, such as precipitation and thermal expansion due to solar heating of rock surfaces. In this paper, we present a database of measurement time series taken over a period of ∼4 years (December 2014–October 2018) for the deformations of selected tuff blocks in the Coroglio coastal cliff. The monitoring system is implemented on five unstable tuff blocks and is formed by nine crackmeters and two tiltmeters equipped with internal thermometers. The system is coupled with a total weather station, measuring rain, temperature, wind and atmospheric pressure and operating from January 2014 up to December 2018. Measurement frequencies of 10 and 30 min have been set for meteorological and deformation sensors respectively. The aim of the measurements is to assess the magnitude and temporal pattern of rock block deformations (fracture opening and block movements) before block failure and their correlation with selected meteorological parameters. The results of a multivariate statistical analysis of the measured time series suggest a close correlation between temperature and deformation trends. The recognized cyclic, sinusoidal changes in the width (opening–closing) of fractures and tuff block rotations are ostensibly linked to multiscale (i.e., daily, seasonal and annual) temperature variations. Some trends of cumulative multi-temporal changes have also been recognized. The full databases are freely available online at: https://doi.org/10.1594/PANGAEA.896000 (Matano et al., 2018) and https://doi.org/10.1594/PANGAEA.899562 (Fortelli et al., 2019).

Bagnoli-Coroglio is a Site of National Interest (SNI) facing the Pozzuoli Bay that has been the place of an industrial activity for more than a century (1854-1985). The modern coastal geology of this area results from the recent evolution of an antecedent volcanic landscape that originated after a caldera collapse following the eruption of Neapolitan Yellow Tuff (NYT) of Campi Flegrei (15 ka). After the NYT eruption, a shallow marine depression formed within the caldera collapse area that underwent progressive filling-up, due to volcaniclastic sediment input from the caldera borders, within a semi-enclosed source-to-sink system. The integrated interpretation of the Digital Terrain Model (DTM) of the Bagnoli-Coroglio area and the high resolution reflection seismic profiles acquired off the Pozzuoli Bay suggests that the present-day coastal plain of Bagnoli-Fuorigrotta and conterminous continental shelf represent the latest infilling phase of the annular depression (caldera ‘collar’) between the structural border of the NYT caldera and the inner caldera resurgent dome. The stratigraphic architecture and morpho-bathymetry of the Bagnoli inner shelf provide a record of the complex interplay between eustatic sea level changes, volcano-tectonic (ground/seafloor) deformation, and supply of volcaniclastic sediments, with associated coastline shifts over the last millennia. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.

Very high-resolution, single channel (IKB-Seistec™) reflection profiles acquired offshore the Napoli Bay, complemented with geological and geophysical data from the literature, provide unprecedented, superb seismic imaging of the Latest Pleistocene-Holocene stratigraphic architecture of the submerged sectors Campi Flegrei and Somma-Vesuvius volcanic districts. Seismic profiles were calibrated by gravity core data and document a range of depositional systems, volcanic structures and hydrothermal features that evolved after the onset of the Last Glacial Maximum (ca. 18 ka BP) over the continental shelf on the Campania coastal zone.Seistec profiles from the Pozzuoli Bay yield high-resolution images of the shallow structure of the collapse caldera-ring fault - resurgent dome system associated with the eruption of the Neapolitan Yellow Tuff (NYT) (ca 15 ka BP) and support a working hypothesis to assess the timing and the styles of deformation of the NYT resurgent structure throughout the Latest Quaternary. Seismic images also revealed the nature of the fragile deformation of strata along the NYT ring fault system and the occurrence of hydrothermal fluids and volcanic/sub-volcanic intrusions ascending along the ring fault zone. Seismic data acquired over the continental shelf off the Somma-Vesuvius stratovolcano, display evidence of gravitational instability of sand wave deposits originated by the underwater modification of pyroclastic flows that entered the seawater after destroying the Roman city of Herculaneum during the 79 CE eruption of Vesuvius.At the Banco della Montagna, a hummocky seafloor knoll located between the Somma-Vesuvius and the Pozzuoli Bay, seismic profiles and gravity core data revealed the occurrence of a field of volcaniclastic diapirs formed by the dragging and rising up of unconsolidated pumice, as a consequence of fluid overpressure at depth associated with active degassing and fluid venting at the seafloor.

The amount of coastal subsidence on the Sele River coastal plain has been examined and measured with local vertical land movement data. The vertical displacements, derived by satellite radar differential interferometry processing (Ps-InSAR), show that the analysed coastal sector is characterised by a southeastward decrease of vertical subsidence rates. These results have been coupled with sea-level rise (SLR) scenarios, in order to identify the most critical areas. In general, the subsidence mostly affects areas where alluvial deposits are thicker, the back-dune areas and the Sele River mouth, all late Holocene in age. Five local SLR scenarios allow identifying zones in the plain potentially prone to inundation and the shoreline retreat for the years 2065 and 2100. For these dates, 2.2% and 7.06% of the investigated area will have a topography lower than the estimated future sea level. Moreover, results show that the extent of the areas potentially exposed to inundation and erosion increases moving from south to north.

Geomorphic evolution of sea cliffs has significant impact on coastal settlements worldwide, so that evaluation of cliff instability processes, failure factors, and retreat rates involves a growing number of scientists for coastal risk and management purposes. Aerial photogrammetry and lidar are among the most used techniques for topographic characterization and geomorphic monitoring of coastal environments. A crucial role in the combined use of such techniques is the evaluation of different spatial accuracy and co-registration between derived terrain models, so that a robust error analysis is required. In this study, we present a change detection analysis of the Torrefumo coastal cliff, in the Campi Flegrei volcanic area (Southern Italy). Aerial images taken in 1956 and 1974, processed through digital photogrammetry, and an airborne lidar point cloud acquired in 2008 were used to produce Digital Elevation Models of the cliff. The analysis was based on the multi-temporal comparison of these models and included the calculation of volumetric changes and average retreat rates of the cliff face with reference to the 1956–1974 and 1974–2008 time intervals. The spatially variable elevation uncertainty of each Digital Elevation Model was evaluated with a probabilistic approach based on the fuzzy set theory. The results of this study showed significant eroded volumes during the period 1956–1974 and relatively smaller volumes in the 1974–2008 time span, with mean annual retreat rates of 1.2 m/year and 0.17 m/year, respectively. We infer that the significant decrease of erosion characterizing the second period was induced by the sheltering effect at the base of the cliff produced by the construction of a seawall in the early 80’s.

In this study, we present the results of an analysis of Terrestrial Laser Scanning (TLS) datasets, referred to multi-temporal (2013-2015) acquisition, aimed at evaluating volumetric changes and average retreat rates of the Coroglio tuff cliff, located in the western sector of Naples (Italy) in the Campi Flegrei caldera. The multi-temporal analysis was carried out in two steps: firstly, we developed a preliminary 3D Cloud-to-Cloud comparative analysis of point clouds obtained by TLS data processing, providing a view on geomorphological evolution; secondly, we obtained quantitative information by analyzing in GIS processing the differences between multi-temporal Digital Elevation Models. Finally, a morphometric analysis was carried out in order to evaluate retreat both retreat and failure rates. Four types of landslides (rock fall, debris fall, earth flow, and soil slip) have been accurately mapped in the different sectors of the cliff.The morphological analysis shows that several morphological variations have been recognized in different areas of the cliff with a maximum retreat of 8 m at the foot of the cliff due to the erosive action of the sea on poorly lithified deposits. We estimated that the average linear retreat rate related to the Coroglio cliff between 2013-2015, was equal to 0.07 m/yr; the linear retreat rate is higher (0.34 m/yr) at the base of the cliff, directly beaten by the sea waves. The results of the statistical analysis of the relationship between volume and area calculated for rock falls are consistent with the results of previous studies. Geo-structural analysis confirms that some discontinuity sets strongly control the failure kinematisms.

This study presents the results of a Terrestrial Laser Scanner (TLS) application aimed at characterizing the structural pattern of Punta Epitaffio tuffaceous coastal cliff, Pozzuoli Bay, Eastern Tyrrhenian margin. The study site is located in the Campi Flegrei, an active volcanic caldera, characterized by dense urbanization, near the town of Naples, Italy. The 3D digital model of the Punta Epitaffio cliff derived from TLS data, provided a base for the classification of rock discontinuities by geostatistical analysis. In particular, the work flow of geostructural data processing included: 1) statistical analysis of spatial orientation of the facets of the 3D mesh derived by the TLS survey; 2) extraction of the best-fit attitudes (dip and dip direction) of discontinuity sets for each sub-planar patch of the rock face; 3) cluster analysis of best-fit structural discontinuities; 4) definition of all the discontinuity sets and geo-structural classification of 3D model facets; 5) kinematic analysis for the definition of possible failure mechanisms. Kinematic analysis took into account primarily structurally-controlled failure mechanisms (planar sliding, wedge sliding, flexural toppling, and direct toppling). The method illustrated in this research can be extensively applied to identify unstable areas along tuffaceous coastal cliffs and define shape and volume of rocks potentially involved by failures.

Small-scale buried structures in volcanic environments could present an extreme relevance, due to their link to the eruptive activity of in- dividual monogenetic edi ces, but require, to be detected, a high-reso- lution geophysical imaging. In such context, the Electrical Resistivity Tomography is often able to recover primary knowledge about the heterogeneity of the buried layers, despite the reduced investigation depth. In this paper an example of such matter is proposed, concern- ing the Posillipo hill, in the southeastern sector of the Campi Flegrei Caldera (Italy), where an electrical resistivity survey has been car- ried out in the roman age Seiano tunnel. In such a way, details of the Trentaremi tuff cone buried structure have been revealed, with a maximum depth of exploration of about 100 m. The obtained re- sults have been compared with geological observations on the exposed rocks, interpreting their underground continuation. The geophysical image reconstructs the inner structure of the Trentaremi cone. At the same time, its relationships with respect to the deposits belonging to Neapolitan Yellow Tuff eruption have been highlighted. Reconstruct- ing this stratigraphic sequence, indications about the past volcanic dynamics have been obtained, presenting valuable implications for the future activity forecasting.