The Hydrothermal System of Solfatara Crater (Campi Flegrei, Italy) Inferred From Machine Learning Algorithms

Two machine learning algorithms were applied to three multivariate datasets acquired at Solfatara volcano. Our aim was to find an unbiased and coherent synthesis among the large amount of data acquired within the crater and along two orthogonal vertical NNE- and WNW-trending cross-sections. The first algorithm includes a new approach for a soft K-means clustering based on the use of the silhouette index to control the color palette of the clusters. The second algorithm which uses the self-organizing maps incorporates an alternative method for choosing the number of nodes of the neural network which aims to avoid the need for downstream clustering of the results of the classification. Both methods achieved an objective characterization of the shallow hydrothermal system of the volcano, enhancing and highlighting subtle geophysical anomalies likely correlated to structural pathways of deep magmatic degassing. Comparison between the results of K-means and self-organizing maps on the datasets with the largest number of nodes confirms that, with respect to the K-means, self-organizing maps compress the data in a way that better highlights finer details of the original data. However, the choice of the coloring scheme of the neurons is critical for an effective visualization of the results. Unsupervised integration of the three multivariate datasets allowed us to spatially correlate, with a high-degree of confidence, the geophysical anomalies recorded at the surface of the crater with those recorded at the subsurface along the two cross-sections. it also allowed us to associate those anomalies to different hydrothermal features such as shallow gas-saturated and water-saturated zones and their underlying fractures/faults feeding system. Our results suggest that the main shallow structural patterns, which influence the hydrothermal dynamics at Solfatara volcano, remained substantially unchanged in the last fifteen years. Our approach shows that the use of clustering methods to interpret multivariate data reduces interpretation uncertainties and achieves an improved understanding of the complex dynamics occurring in volcanoes

Potential shallow aquifers characterization through an integrated geophysical method: multivariate approach by means of k-means algorithms

The need to obtain a detailed hydrogeological characterization of the subsurface and its interpretation for the groundwater resources management, often requires to apply several and complementary geophysical methods. The goal of the approach in this paper is to provide a unique model of the aquifer by synthesizing and optimizing the information provided by several geophysical methods. This approach greatly reduces the degree of uncertainty and subjectivity of the interpretation by exploiting the different physical and mechanic characteristics of the aquifer. The studied area, into the municipality of Laterina (Arezzo, Italy), is a shallow basin filled by lacustrine and alluvial deposits (Pleistocene and Olocene epochs, Quaternary period), with alternated silt, sand with variable content of gravel and clay where the bottom is represented by arenaceous-pelitic rocks (Mt. Cervarola Unit, Tuscan Domain, Miocene epoch). This shallow basin constitutes the unconfined superficial aquifer to be exploited in the nearly future. To improve the geological model obtained from a detailed geological survey we performed electrical resistivity and P wave refraction tomographies along the same line in order to obtain different, independent and integrable data sets. For the seismic data also the reflected events have been processed, a remarkable contribution to draw the geologic setting. Through the k-means algorithm, we perform a cluster analysis for the bivariate data set to individuate relationships between the two sets of variables. This algorithm allows to individuate clusters with the aim of minimizing the dissimilarity within each cluster and maximizing it among different clusters of the bivariate data set. The optimal number of clusters "K", corresponding to the individuated geophysical facies, depends to the multivariate data set distribution and in this work is estimated with the Silhouettes. The result is an integrated tomography that shows a finite number of homogeneous geophysical facies, which therefore permits to distinguish and interpret the porous aquifer in a quantitative and objective way

Association between preoperative evaluation with lung ultrasound and outcome in frail elderly patients undergoing orthopedic surgery for hip fractures: study protocol for an Italian multicenter observational prospective study (LUSHIP)

Hip fracture is one of the most common orthopedic causes of hospital admission in frail elderly patients. Hip fracture fixation in this class of patients is considered a high-risk procedure. Preoperative physical examination, plasma natriuretic peptide levels (BNP, Pro-BNP), and cardiovascular scoring systems (ASA-PS, RCRI, NSQIP-MICA) have all been demonstrated to underestimate the risk of postoperative complications. We designed a prospective multicenter observational study to assess whether preoperative lung ultrasound examination can predict better postoperative events thanks to the additional information they provide in the form of "indirect" and "direct" cardiac and pulmonary lung ultrasound signs

Structure from Motion technique of proximal-sensing airborne data for 3D reconstruction of extraction sites

9nohttp://www.stat.immcarrara.com/uploads/files/1084it-EBOOK-SUSTONE-WEB3.pdfopenDigital photogrammetry based on Structure from Motion (SfM) algorithms nowadays represents a low-cost, valid and rapid technique for the tridimensional detection and mapping of large areas of particular geologic-geomorphologic, natural and environmental interest. Products derived from the photogrammetric processing, such as tridimensional point clouds, digital surface and terrain models (DSM and DTM), and high-resolution orthophotos, allow to study and monitor the territory and its productive activities. In this case study we used images captured from a small aircraft, agile and extremely inexpensive, for the 3D reconstruction of extraction sites and zones of geo-structural importance. The aircraft, called RadGyro (property of the CGT Group, University of Siena), is able to deal with complex flight plans and low altitudes in a way to make possible the detailed detection of desired features even in very complex areas. An example of this complex situation is represented by the test area here presented, located in the marble district of the Apuan Alps, the biggest and most exploited European extractive basin. The aircraft is equipped to acquire series of photos in an independent manner, using two digital cameras characterized by a full frame sensor and 35 mm fixed lens. Moreover, five GPS antennas and an inertial navigation system (INS) allow associating to each frame the position and the angular orientation of the camera. Flying at an altitude varying from 100 m to 400 m above ground level, the cameras can detect about 50 km2 and 200 km2, respectively, with a ground resolution of 3.5 cm and 10.0 cm. The exterior orientation of images can be improved, if necessary, acquiring some ground control points through traditional topographic survey. Info about the exterior orientation, associated to each frame, is therefore used to finalize the photogrammetric processing, using appropriate software. Structure from Motion techniques and algorithms allow to detect millions of "tie points" necessary for the accurate alignment of photos. The photogrammetric processing, then, is finalized by the creation of 3D point clouds, DSM, DTM and orthophotos. These products are used in this case study for the detailed analysis of the marble quarries morphology and geology and, through a multitemporal acquisition, for the assessment of the volumetric variations related to the extraction activities. Moreover, we want to point out, finally, how the RadGyro is able to provide data for environmental researches thanks to the following additional equipment: an hyperspectral camera in the range from 400 nm to 1000 nm, a thermal camera (7500 -1300 nm) and a gamma ray spectrometer equipped with detectors.openTufarolo, E.; Salvini, R.; Seddaiu, M.; Bernardinetti, S.; Petrolo, F.; Lanciano, C.; Carmignani, L.; Massa, G.; Pieruccioni, DTufarolo, Emanuele; Salvini, Riccardo; Seddaiu, M.; Bernardinetti, Stefano; Petrolo, F.; Lanciano, C.; Carmignani, Luigi; Massa, Giovanni; Pieruccioni, D

A pilot study to test the reliability of the ERT method in the identification of mixed sulphides bearing dykes: The example of Sidi Flah mine (Anti-Atlas, Morocco)

A multidisciplinary study, comprising geological, petrographical and geophysical methods, was carried out for the identification and the geometrical and volumetric assess of the main mineralized bodies (mixed sulphides, Zn-Pb and Fe-Cu) in the area of the Anti-Atlas chain, located at SW of the town of Sidi Flah (Ouarzazate, Morocco). The initial phase of exploration involved an extensive fieldwork (structural investigations and sampling) and a detailed survey for verifying the effectiveness and reliability of the Electrical Resistivity Method (ERT). Geological fieldworks and laboratory analyses played a fundamental role in identifying the resistivity anomalies and constraining tomographic results. Main issues we focused on are: i) mineralized bodies imaging according to the electrodic step; ii) consistency with geometry of mineralized bodies; iii) contrast of electrical resistivity between mineralized dykes and host rocks; iv) possible correlations between the type and amount of sulphides and electrical resistivity

Multivariate Analysis Applied to Aquifer Hydrogeochemical Evaluation: A Case Study in the Coastal Significant Subterranean Water Body between “Cecina River and San Vincenzo”, Tuscany (Italy)

The hydrogeochemical characteristics of the significant subterranean water body between “Cecina River and San Vincenzo” (Italy) was evaluated using multivariate statistical analysis methods, like principal component analysis and self-organizing maps (SOMs), with the objective to study the spatiotemporal relationships of the aquifer. The dataset used consisted of the chemical composition of groundwater samples collected between 2010 and 2018 at 16 wells distributed across the whole aquifer. For these wells, all major ions were determined. A self-organizing map of 4 × 8 was constructed to evaluate spatiotemporal changes in the water body. After SOM clustering, we obtained three clusters that successfully grouped all data with similar chemical characteristics. These clusters can be viewed to reflect the presence of three water types: (i) Cluster 1: low salinity/mixed waters; (ii) Cluster 2: high salinity waters; and (iii) Cluster 3: low salinity/fresh waters. Results showed that the major ions had the greater influence over the groundwater chemistry, and the difference in their concentrations allowed the definition of three clusters among the obtained SOM. Temporal changes in cluster assignment were only observed in two wells, located in areas more susceptible to changes in the water table levels, and therefore, hydrodynamic conditions. The result of the SOM clustering was also displayed using the classical hydrochemical approach of the Piper plot. It was observed that these changes were not as easily identified when the raw data were used. The spatial display of the clustering results, allowed the evaluation in a hydrogeological context in a quick and cost-effective way. Thus, our approach can be used to quickly analyze large datasets, suggest recharge areas, and recognize spatiotemporal patterns

Structure from motion technique of proximal sensing airborne data for 3D reconstruction of extraction sites

Nowadays digital photogrammetry utilized together with Structure from Motion (SfM) algorithms represents a low-cost and rapid technique for the tridimensional detection and mapping of large areas of particular geologic-geomorphologic and environmental interest. In this case study, we use images captured from sensors mounted on a small and inexpensive aircraft for the 3D morphological reconstruction of extraction sites. The aircraft, called RadGyro, is able to deal with morphologically complex zones, as the test area, located in the marble district of the Apuan Alps, the biggest and most exploited European extractive basin. The RadGyro is equipped with two digital cameras (full frame sensor and 35 mm fixed lens), five GPS antennas, and an Inertial Navigation System (INS) that allow association of each frame to the camera position and its angular orientation. Ground Control Points (GCPs) acquired through traditional topographic surveys allow improvement of the image exterior orientation as well as the SfM techniques permit detecting millions of tie points for an accurate relative alignment of photos. Finally, the photogrammetric processing is completed by creating 3D point clouds, Digital Surface Models (DSM), Digital Terrain Models (DTM), and orthophotos. The results, here presented, emphasize the potentials of the RadGyro and demonstrate how SfM algorithms can be very useful in the photogrammetric processing and in the geological, geomorphological and geo-structural interpretation and analysis

Tectonic Setting of the Kenya Rift in the Nakuru Area, Based on Geophysical Prospecting

In this paper, we present results of tectonic and geophysical investigations in the Kenya Rift valley, in the Nakuru area. We compiled a detailed geological map of the area based on published earlier works, well data and satellite imagery. The map was then integrated with original fieldwork and cross sections were constructed. In key areas, we then performed geophysical survey using Electrical Resistivity Tomography (ERT), Hybrid Source Audio MagnetoTelluric (HSAMT), and single station passive seismic measurements (HVSR). In the study area, a volcano-sedimentary succession of the Neogene-Quaternary age characterized by basalts, trachytes, pyroclastic rocks, and tephra with intercalated lacustrine and fluvial deposits crops out. Faulting linked with rift development is evident and occurs throughout the area crosscutting all rock units. We show a rotation of the extension in this portion of the Kenya rift with the NE–SW extension direction of a Neogene-Middle Pleistocene age, followed by the E–W extension direction of an Upper Pleistocene-Present age. Geophysical investigations allowed to outline main lithostratigraphic units and tectonic features at depth and were also useful to infer main cataclasites and fractured rock bodies, the primary paths for water flow in rocks. These investigations are integrated in a larger EU H2020 Programme aimed to produce a geological and hydrogeological model of the area to develop a sustainable water management system

Subsurface 3D modeling of Giumentina Valley (Majella, Abruzzo, Italy) trough multi-methodic geophysical surveys

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