Hydrothermal circulation on Ischia Island (Southern Italy), revealed by an integrated geochemical, geophysical and geological approach

Volcano-hosted hydrothermal systems are complex geological objects, whose thorough characterisation requires extensive and interdisciplinary work. Indeed, even thought geological, geochemical and geophysical observations offer highly significant but independent information, only an integrated multidisciplinary approach can yield a comprehensive characterisation of the chemical/physical structure of hydrothermal systems. Notwithstanding the extensive application of geological, geochemical and geophysical techniques in geothermal research, there are only a few examples in the literature of concurrent use of the three techniques [Finizola et al., 2002; Zlotnicki et al., 2009]; these studies ov…

La sicurezza nell'identità dei beni culturali in materiali lapidei: la firma sonica

Caratterizzazione geofisica dell’acquifero idrotermale dell’area di Panza (Ischia)

Gli obiettivi di questo lavoro sono quelli di ricostruire, con metodologie geofisiche integrate, le principali geometrie tettoniche ed idrogeologiche del territorio di Panza nell'isola di Ischia. La zona è stata scelta in quanto caratterizzata da un'intensa attività idrotermale e deformativa connessa con la presenza di un reservoir geotermico.

The Ischia Island hydrothermal system: an integrated multidisciplinary (geochemical, geophysical and geological) study

Ischia Island is the emergent portion of a large volcanic complex on the Gulf of Naples (Southern Italy). Ischia volcano has undertaken a complex evolution since 150 ka b.p., with prolonged cycles of effusive and explosive eruptions alternated with quiescence periods (the most recent of which started after the 1302 A.D. Arso eruption). Currently, hot springs (with discharge temperature up to 90 C), fumarolic gas emissions with CO2 up to 97%, and diffuse soil degassing testify a persistent activity state of the Ischia volcano. Ischia Island is a very good example of an active volcano hosting a large hydrothermal system and, in particular, its south-western sector has long been known to be th…

Geophysical study of the hydrothermal reservoir in the Panza area (Ischia, Italy)

The aim of the work is the reconstruction of the main geometric pattern and the characterisation with geophysical parameters of geological structures lying at small and medium depths in an area of the Ischia island (Italy), where a sensible hydrothermal activity is present.

ERT and IPT surveys to check the integrity of the geomembrane in the landfill of Bellolampo (Palermo, Italy)

In landfills, changes in resistivity and chargeability can be related to the characteristics of the waste and they can be abrupt and considerable within short distances. These physical properties are function of generation, mobility and degree of saturation of the leachate, gas generation, compaction density and variability. These relationships mean that it can be possible to get an overall image of the quantity and characteristics of the waste from surface electrical measurements over the landfill. In this paper, we present and discuss the results of three electrical tomographies carried out in the landfill site of Bellolampo (Palermo, Italy). The main aim of these surveys was to check the…

Influence of different array datasets on reliability of electrical resistivity tomography

The goal of this work is to study how the reliability of inverse model depends on a few basic parameters, as the combination of potential spacing and dipolar distance and, consequently, the number of measurements and of current dipoles, considering also how error affects inversion. The number of current dipole used is crucial, when using multichannel resistivity-meters, because it determines the overall acquisition time. A systematic comparison is presented between four 2D resistivity models and their images, obtained by the inversion of synthetic datasets relating to four different arrays: dipole-dipole (DD), pole-dipole (PD), Wenner-Schlumberger (WS) and multiple gradient (MG). For DD, PD…

Remotely controlled aerial and underwater vehicles in support to magnetic surveys

This article deals with the creation of a professional magnetometer, a flexible, light and compact instrument that can be installed on aerial and marine drones. The instrument can accurately measure the local magnetic field. Subsequently, it was installed on AUV and a micro ROV to test its effectiveness for archaeological purposes and magnetic surveys. Experimental data show that both systems can be used by filtering disturbances from vehicles.

Metodo ed apparato di rilevamento tomografico di una distribuzione di resistività in un mezzo

Metodo di rilevamento tomografico di una distribuzione di resistività di un mezzo comprendente tre fasi: predisposizione su una porzione della superficie del mezzo di una griglia di elettrodi collegati con almeno un generatore elettrico; selezione dalla griglia di una pluralità di secondi elettrodi collegati con un misuratore di potenziale elettrico; immissione attraverso la prima coppia di elettrodi di una corrente elettrica suscettibile di generare un campo elettrico nel mezzo; misurazione dei potenziali elettrici in corrispondenza dei secondi elettrodi per ricavare differenze di potenziale tra coppie a scelta di secondi elettrodi; calcolo della distribuzione di resistività mediante le di…

Evidence of surface faulting in the archaeological site of Santa Venera al Pozzo (Catania-Eastern Sici-ly): first results from geophysical investigations

We present the first results of a preliminary geological and geophysical survey carried out in the archaeological site of Santa Venera al Pozzo (Catania, Italy). The site dates back to the Roman Age, (1st century BC). Geological surveys highlighted a set of remarkable fractures affecting some archeological remains, suggesting the occurrence of a capable fault zone through the area. Multidisciplinary geophysical surveys (seismic refraction and electrical resistivity tomographies, together with aerial photographic and thermographic survey) identified a main tectonic discontinuity ascribable to the fault zone, allowing us to infer that the fractures observed at surface could be the evidence of…

An Overview of Geophysical Techniques and Their Potential Suitability for Archaeological Studies

The need to study, protect, and conserve archaeological heritage has enhanced the application of geophysical techniques as non-invasive and reliable tools to investigate fragile and valuable assets. This review presents the most popular geophysical techniques suitable for archaeogeophysical investigations, namely, magnetometry, ground penetrating radar, and electrical resistivity tomography, together with a series of multiparametric measures taken from aerial platforms (UAS). For each method, we recall the basic physical principles, illustrate the operative procedures for field investigation, and provide indications about data processing and modeling. We propose a flowchart to address relia…

New Perspectives on Geophysics for Archaeology: A Special Issue

This Special Issue hosts a selection of papers presented at the Third International Conference on Metrology for Archaeology and Cultural Heritage (Lecce, Italy, 23-25 October 2017), related to the new perspectives on geophysics for archaeology. In recent years, archaeological prospecting has seen major advances through a variety of remote sensing and computing technologies. Geophysical instrumentation continues to improve in sensitivity and acquisition speed, and new multi-sensor arrays, e.g., drawn by carts over land, now permit vast areas to be rapidly covered. On the other hand, the availability of highresolution remote sensing techniques provides multiscale and multi-temporal approaches…

La metodologia MYG per eseguire tomografie elettriche 3D su oggetti che presentano una superficie di pregio artistico

La tomografia elettrica di resistività è poco utilizzata nello studio delle murature di edifici di pregio artistico, malgrado le potenzialità in termini di risoluzione: attraverso indagini tridimensionali è infatti possibile ottenere tomografie di resistività 3D dettagliate e rappresentative. La necessità di inserire "chiodini" per immettere la corrente ne limita però l’applicabilità su superfici di pregio. Abbiamo superato questa limitazione sviluppando una metodologia (MYG) che riduce drasticamente rispetto ai metodi classici il numero degli elettrodi utilizzati per immettere la corrente (circa15 volte) ed il tempo di acquisizione (circa 50 volte), permettendo l'uso di elettrodi non invas…

The MYG methodology to carry out 3D electrical resistivity tomography on media covered by vulnerable surfaces of artistic value

Electrical Resistivity Tomography (ERT) is not yet frequently used in the study of walls, floors and foundations of buildings of artistic value, like Ground Penetrating Radar (GPR) or other commoner techniques, although it exhibits a great potentiality in terms of resolution power. The main limitation for the applicability of ERT to the Cultural Heritage field arises from the method of current injection: it is often necessary to drive current electrodes into small perforations on the acquisition surface in order to get a current flow sufficient to obtain a good signal-to-noise ratio. To overcome this limitation the Maximum-Yield Grid (MYG) methodology has been developed, in which only a small fr…

Seismic microzonation by means of cluster analysis

The identification of areas with uniform behaviour in seismic perspective is a very complex task that involves the simultaneous assessment of many parameters. In this paper we propose an automatic procedure for the seismic microzonation based on cluster analysis and performed by means of an agglomerative hierarchical algorithm. It exploits a proximity matrix specifically defined on the parameters space and the average linkage criteria. The procedure has been used to carry out the expedite seismic microzonation of some high seismic hazard areas, only using the data inferred by the extensive application of the HVSR technique. The results of the clustering procedures have been assessed from a …

Cluster analysis to support microzonation studies

In recent times the use of microtremor techniques for subsoil investigation increased significantly. The use of HVSR (Horizontal to Vertical Spectral Ratio)technique for seismic microzoning studies allows in many case to obtain detailed reconstruction of the roof of the seismic bedrock and to identify areas with similar seismic behaviour. Two different algorithms of clusteringhave been tested on a HVSR datasets acquired for studies of seismic microzoning in various Sicilian urban centers. HVSR data were previously properly processed to extract frequency and amplitude of peaks by a code based on clustering of HVSR curves determined in sliding time windows.To select an optimal set of time win…

Hydrogeological and geotechnical modeling of the foundation soils of Maredolce Lake in Palermo, aided by geophysical surveys

The cultural heritage of Maredolce (Palermo) includes an Arab-Norman castle that originally stood on the shores of an artificial lake carved out of a basin dug out of the calcarenite and filled with water thanks to the channeling of the springs of San Ciro upstream. Subsequently, the lowering of the water table and the high hydraulic permeability of the outcropping rocks caused the lake to dry up. Recently, a project of enhancement of the cultural heritage required the restoration of the lake. The geophysical study presented here, including the integrated use of different techniques such as electrical and seismic tomography, Multichannel Analysis of the Surface Waves and ambient vibration r…

A constrained geophysical model of the landslide that affects the Agrigento Cathedral

Ricerche Geofisiche di resti archeologici sotto la cattedrale di Tarragona (Spagna): Tomografia Geoelettrica (2d E Full-3d) e Gpr

Integrated geophysical surveys in the tarragona cathedral

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to detect the existence of archaeological remains of the Roman’s temple devoted to August. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most famous temple of Spain (12th century) evolving from Romanesque to Gothic styles. A project including electrical resistivity tomography (ERT), ground probing radar (GPR) and frequency domain electromagnetics (FDEM) has been planned over one year and conducted during a week of intensive field survey. From all the methods applied, both ERT and GPR…

The Sonic Imprint to identify and monitor precious artefacts: further developments

A new non-invasive technique, developed to univocally identify and monitor the integrity of precious artefacts, like potteries, statues and objects, generally made of stone, metal or wood, has been already presented (2). This technique responds to the demand, especially felt among museum managers, of an art collection cataloguing which allows the identification of artefacts and the assessment of their physical conditions. This is also linked to the international loan of precious artefacts, which are then subjected to transport stresses and to the connected risks (damages, substitutions, physical deterioration, etc.). Furthermore, in these days many art exhibitions are itinerant, and the art…

Improvement of HVSR technique by cluster analysis

The Horizontal to Vertical Spectral Ratio (HVSR) technique, applied to ambient noise, is widely used to quickly estimate the fundamental frequency of a site. The HVSR technique is based on numerous assumptions about the propagation medium and the nature of the seismic noise, often hard to verified. In addition, in order to obtain reliable results, several acquisition and processing criteria must be respected. One of the most controversial aspects in the technique implementation are the reliable criteria for the identification in the microtremors signals of time windows appropriate for the calculation of the HVSR curves. Several authors suggest to remove spikes and transients because they br…

Centroid-based Cluster Analysis of HVSR Data for Seismic Microzonation

Horizontal to Vertical Spectral Ratio (HVSR) datasets acquired for studies of seismic microzoning in various urban centers of Sicilian towns, have been used to test clustering analysis through a nonhierarchical centroid-based algorithm. In this context clustering techniques may be useful to identify areas with similar seismic behaviour through HVSR data. Centroid-based algorithms generally require the number of clusters, k, and the initial centroid coordinates to be specified in advance. This aspect is considered to be one of the biggest drawbacks of these algorithms. The proposed algorithm doesn’t limit the number of k clusters and choose the initial centroids automatically from the data s…

Le tecniche geofisiche per lo studio degli acquiferi costieri soggetti ad intrusione marina: l’acquifero di Petrosino (TP)

Un’indagine geofisica è stata condotta nella zona costiera di Petrosino, situata in Sicilia Sud-Occidentale tra i paesi di Marsala e di Mazara del Vallo, per uno studio dell’evoluzione temporale del fenomeno dell’intrusione di acqua marina nella falda costiera, accentuato presumibilmente dalle attività antropiche. L’eccessivo sfruttamento della falda acquifera dovuto a un intensivo uso agricolo ha modificato significativamente il naturale assetto idro-geochimico del bacino, accentuando il fenomeno intrusivo già di per sé critico nella zona. Lo studio è stato basato sull’elaborazione integrata di dati idrogeologici, geochimici e geofisici (sondaggi elettromagnetici TDEM), disponibili grazie …

A Fast Imaging Technique Applied to 2D Electrical Resistivity Data

A new technique is proposed to process 2D apparent resistivity datasets, in order to obtain a fast and contrasted resistivity image, useful for a rapid data check in field or as a starting model to constrain the inversion procedure. In the past some modifications to the back-projection algorithm, as well as the use of filtering techniques for the sensitivity matrix were proposed. An implementation of this technique is proposed here, considering a two-step approach. Initially a damped least squares solution is obtained after a full matrix inversion of the linearized geoelectrical problem. Furthermore, on the basis of the results, a subsequent filtering algorithm is applied to the Jacobian ma…

NEW 3D ELECTRICAL TOMOGRAPHY TECHNIQUE FOR INVESTIGATIONS ON VULNERABLE SURFACES

The integration of surface and subsurface stratigraphic data with HVSR measures for studies of seismic microzonation: the case of Oliveri (ME)

Because of its high seismic hazard the urban area of Oliveri has been subject of a study on seismic microzonation at first level (OPCM 3907/2010). The urban area develops on a large coastal plain made of Late Pleistocene and Holocene mixed fluvial/marine sediments, that mainly consist of silty sands and gravels. The eastern part of this plain is dominated by the alluvial deposits of the Elicona torrent. The coastal and alluvial sediments overlap a complexly deformed substrate made of Hercynian metamorphites (Aspromonte unit), the Capo d’Orlando Flysch, the Antisicilide Argille Scagliose and Pleistocene clays and calcarenites. This area is affected by high uplift rates as recently estimated …

Seismic tomography tests applied to a gravity dam

The control of the safety assessment of a dam is largely dependent on knowledge of the mechanical parameters of the actual construction, as well as its geological substratum. The application of geophysical methods can be used in existing dams to evaluate the materials (strength properties) and to verify if they match design expectations, as well as to contribute to the safety control. In particular seismics methods can considerably contribute to the examination indicating the less consolidated material and the degradation of mechanical parameters. For the characterization of the concrete conservation three seismic tomographies and a vertical seismic profile on the dam body were performed.Th…

Microgeofisica per lo studio dei beni culturali movimentabili

Seismic Characterization by Inversion of HVSR Data to Improve Geological Modelling

SUMMARY An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of geological reconstruction of the subsoil finalized to studies of seismic microzonation of heavily urbanized areas, where few stratigraphic and geophysical constraints are available and most of the information are derived from the geological maps. In such cases the uncertainty of the results is is enhanced by doubts on the nature of the H/V peaks, not always caused by stratigraphic discontinuities, and to the subjective choices done especially in the step of signal preprocessing. The investigated area (Altavilla Milicia, Sicily) includes the town center and the adjacen…

Geomorphological and geophysical investigations to study the landslide affecting the archaeological site of abakainon

In recent years, a detailed archeoseismological investigation has been carried out in the necropolis of Abakainon in order to identify traces of an ancient earthquake. Although the identification of seismic damage was undoubtedly attributed to the 1st century AD earthquake, it was hypothesised that the level of damaging observed in the necropolis, as well as the counter slope tilting of the tomb basements may have also caused by a seismo-induced landslide, which produced locally an amplification of the seismic shaking. In order to identify the landslide, on which the Greek site lies, detailed geomorphological and geophysical surveys have been carried out. The research was directed to the ac…

Studi di base per il monitoraggio elettrotomografico dell’intrusione salina dell’acquifero di Petrosino

Indagini nell'area ad ovest del Tempio della Vittoria ad Himera

Himera: New investigations in the area West of the Tempio della Vittoria · The University of Palermo has started a new cycle of field investigations in the “lower town” of Himera, with the aim of answering some questions about the relationships between the Tempio della Vittoria, the residential districts, and the agora, that remained to be clarified after the important results produced by the studies on the urban development of the Greek city over the past forty years. This paper presents some initial results and research perspectives from the first excavation soundings and geophysical survey of 2021. The first findings strongly suggest that the agora extended much further south than previo…

Seismic and non‐invasive geophysical surveys for the renovation project of Branciforte Palace in Palermo

The renovation project of the historic Branciforte Palace (16th–17th century) in Palermo (Italy) was owned by the Banco di Sicilia Foundation, with the aim for it to become a multi-purpose centre for the promotion of exhibitions and cultural events. In the context of the restoration work, a multi-methodological and non-invasive geophysical study has been carried out. The seismic characterization of the foundation soils was obtained by means of joint interpretations of a vertical seismic profile (VSP), multichannel analysis of surface waves (MASW) and horizontal to vertical spectral ratio (HVSR) microtremor analysis. The mutually constrained inversion of seismic surveys carried out with diff…

Integrated full 3D geoelectrical and GPR tomographies in the Ambulatory of the roman “Villa del Casale”(Piazza Armerina)

The “Villa del Casale” is a wonderful Roman Villa excavated in the archaeological site of Piazza Armerina (Sicily) in 1929. Its interest is mainly to be referred to the floor mosaics, among the largest and most beautiful ones of Roman times, of superlative quality. The floor of the Corridor is covered by a wonderful mosaic depicting the hunt and capture of wild animals, so that it is called the “Corridor of the Great Hunting Scene”. The Villa is now under restoration, and during the planning of the restoration a 3D electrical resistivity tomography was performed on the corridor by using an acquisition grid composed by 704 electrodes. Furthermore 25 GPR profiles with 400 MHz antenna were acq…

New seismological, structural and marine geology constraints for a seismotectonic model of the hinge zone between northern Sicily and southern Tyrrhenian

New ultraportable data logger to perform magnetic surveys

This article presents the realization of a device for magnetic surveys It is a flexible, user-reprogramable, lightweight, and compact tool that can be easily integrated with aerial and marine drones. The device can accurately measure the local magnetic anomalies. It is based on the Atmega 2560 microcontroller and a digital 3-axis fluxgate magnetometer.

Contributo geofisico allo studio dell’intrusione marina nell’area costiera compresa fra Mazara del vallo e Marsala (Sicilia Sud-Occidentale)

Misinterpretation caused by 3D effects on 2D Electrical Resistivity Tomography: tests on simple models

Summary The aim of this work is to evaluate the effects of 2D inversion of electrical resistivity data when in presence on 3D structures by testing synthetic and experimental models. Several numerical simulations have been calculated for different resistivity models and 2D datasets were extracted to study and quantify the effects of 2D inversion on 3D structures. Results have been compared with field texts carried out in quarrying sites. The main tests here presented simulates prism-shaped cavities with a square vertical section of 1 × 1 size and a variable lateral extension d, from 1 to infinity (this latter being a 2D tunnel model). Inversion of predicted data show that 2D tomography does…

ALCUNE MODIFICHE MIGLIORATIVE ALLA BACK-PROJECTION RESISTIVITY TECHNIQUE (BPRT)

SPR survey for archaeological researches: the site of Himera

3D GPR Model in the Military District of San Giacomo Degli Spagnoli (Palermo)

The georadar method was used to try to find some anthropic structures in a large square inside the Carabinieri barracks in the former military complex of San Giacomo degli Spagnoli in Palermo (Italy). These investigations are part of a broader context of a study of the entire area. The purpose of the investigations is to try to understand if under the ground there are the remains of an ancient horse passage that connected the Royal Palace of Palermo with the sea gate of the city. Furthermore, in the Middle Ages, on the site of the present square, there were most likely two churches, which no longer exist, as evidenced by numerous historical testimonies. One of the two, San Giacomo la Mazara…

Georadar Investigations in the Church of San Paolo (San Giacomo Dei Militari, Palermo).

Summary As part of a research project aimed at drawing up a restoration project for the church of San Paolo, the monument was investigated with georadar surveys. The investigations were followed in a targeted manner by archaeological excavations, under the supervision of the Superintendence of Cultural and Environmental Heritage of Palermo. The San Paolo church is located in the oldest part of the city. The geophysical investigations will be useful to identify any pre-existing structures on which the church could be founded. The georadar investigations focused on the central nave and one of the side aisles to identify buried structures and crypts. The data showed several anomalies. One of t…

Indagini microgeofisiche su due dipinti murali di Pietro Novelli

Microgeophysics for the identity of lapideous cultural goods

Use of the linear grid array in 2D resistivity tomography

Integration of constrained electrical and seismic tomographies to study the landslide affecting the cathedral of Agrigento

The Cathedral of Saint Gerland, located on the top of the hill of Agrigento, is an important historical church, which dates back to the Arab–Norman period (XI century). Unfortunately throughout its history the Cathedral and the adjacent famous Archaeological Park of the 'Valley of the Temples' have been affected by landslides. In this area the interleaving of calcarenites, silt, sand and clay is complicated by the presence of dislocated rock blocks and cavities and by a system of fractures partly filled with clay or water. Integrated geophysical surveys were carried out on the north side of the hill, on which the Cathedral of Agrigento is founded, to define lithological structures involved …

Geological modeling of Altavilla Milicia (Sicily) using HVSR data

At today the use of inversion of HVSR curves is mainly limited to derive average parameters of the shear wave velocity, although recently they have been used also for a detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al. 2014). Since ambient vibrations may contain waves travelling in all directions, as body waves and Rayleigh and Love waves, a limit of this method lies in the uncertain composition of seismic noise, in the lack of knowledge about the microseismic field and in the subjective choices regarding the data processing. This work aims to verify the potential and limits of the HVSR inversion for the purposes of geological reconstruction of the subsoil in hea…

Comparative tests on different multi-electrode arrays using models in near-surface geophysics

In this paper, the response of different synthetic models to geoelectrical multi-electrode surveys is studied. The models considered are related to two main problems, which are very common in geophysical research regarding hydrogeology and engineering. The first class of models represents buried walls, similar archaeological remains or remains of buried foundations; the other class corresponds to a sea-water intrusion of a fresh water aquifer, which is generally studied in hydrogeophysics. A set of 2D simulations, starting from the synthetic models, was carried out to compare the behaviour of the different arrays when acquiring measurements of electrical resistivity tomography. For each mod…

Prove di diagnostica dei legni con metodologie di microgeofisica.

Integrated geophysical survey for 3D modelling of a coastal aquifer polluted by seawater

Geophysical surveys are carried out in the coastal area of Petrosino (south-western Sicily) to study the time evolution of seawater contamination of the coastal aquifer, probably increased due to human impact. The overexploitation of the aquifer, due to an intensive agricultural use has affected significantly the natural hydro-geochemical state of the basin. The study is based on a processing and integrated analysis of hydrogeological, geochemical and geophysical data. In particular in the last two years seasonal time-lapse electrical resistivity tomographies (ERT), new TDEM soundings and Multi-Analysis Surface Wave soundings (MASW) have been carried out. The interpretation of the total set…

The structure of a hydrothermal system from an integrated geochemical, geophysical, and geological approach: The Ischia Island case study

The complexity of volcano-hosted hydrothermal systems is such that thorough characterization requires extensive and interdisciplinary work. We use here an integrated multidisciplinary approach, combining geological investigations with hydrogeochemical and soil degassing prospecting, and resistivity surveys, to provide a comprehensive characterization of the shallow structure of the southwestern Ischia's hydrothermal system. We show that the investigated area is characterized by a structural setting that, although very complex, can be schematized in three sectors, namely, the extra caldera sector (ECS), caldera floor sector (CFS), and resurgent caldera sector (RCS). This contrasted structura…

Contribution of HVSR measures for seismic microzonation studies

The HVSR method applied to seismic noise can be a very useful technique to map the site effects of the territory, to identify the thickness of the soft covering and so the depth of the seismic bedrock. The case of the urban area of Oliveri is presented. Because of its high seismic hazard this area has been subject of first level seismic microzonation. The town lies on a large coastal plain made of mixed fluvial/marine sediments, overlapping a deformed substrate. In order to identify points on the area probably suffering of relevant site effects and to define a preliminary Vs subsurface model, 23 HVSR measurements were performed. A clustering technique of continuous signals has been used to …

Evaluation of Artifacts and Misinterpretation in 2D Electrical Resistivity Tomography Caused by Three-Dimensional Resistive Structures of Regular or Irregular Shapes

Electrical resistivity tomography (ERT) is a well-known geophysical method applied to geological, hydrogeological and geoenvironmental research. To date, 2D ERT is still used much more than 3D ERT, thanks to its greater immediacy, survey speed and lower complexity in processing and inversion. However, the assumption of two-dimensionality of the underground structures can mean that the effects of 3D structures on the 2D ERT can sometimes lead to gross errors in interpretation. This work aims to evaluate these effects by testing synthetic and experimental models. Numerical simulations are performed starting from different resistivity models, and from the results, 2D data sets are derived to s…

Indagini geofisiche integrate eseguite a Palazzo Branciforte

Il nuovo stendimento MYG per la tomografia geoelettrica Full 3D

Indagini geofisiche integrate eseguite al Castello di Zena (PC) per lo studio delle fondazioni

Multivariate geophysical survey to detect a shallow fault zone in a landfill project area

An integrated analysis of 2D high-resolution shallow seismic refraction tomographies (SRT) and electrical resistivity tomographies (ERT) has been carried out along a slope where the presence of a fault zone was assumed. It was also applied a post-inversion k-means cluster analysis of the P-wave velocity, the density of the seismic rays and the electrical resistivity of the interpretation models. Distribution maps of the cluster in multi-space were built, allowing to better definethe lateral geometry of a NE-SW directed band composed of intensely tectonized carbonate breccias. Finally, the fracturing and kinematic analysis on fault planes observed along the trenches, highlighted systems of l…

Assessment of a geological model by surface wave analyses

A set of horizontal to vertical spectral ratio (HVSR) and multichannel analysis of surface waves (MASW) measurements, carried out in the Altavilla Milicia (Sicily) area, is analyzed to test a geological model of the area. Statistical techniques have been used in different stages of the data analysis, to optimize the reliability of the information extracted from geophysical measurements. In particular, cluster analysis algorithms have been implemented to select the time windows of the microseismic signal to be used for calculating the spectral ratio H/V and to identify sets of spectral ratio peaks likely caused by the same underground structures. Using results of reflection seismic lines, ty…

A multidisciplinary non-invasive approach in geoarchaeology conducted on the archaeological area of Selinunte

Southwestern Sicily is an area of infrequent seismic activity. Only an earthquake occurred in the Belice valley on 13 January 1968 is reported in the historic earthquake catalogues (see e.g. [1]) as severe event, that is characterized by moderate-high energy (M=6.5) and significant epicentral and local macroseismic intensities (Io=X and I=VII-VIII of the MCS scale). Nevertheless, some studies (e.g. [2]) suggest that probably at least two earthquakes struck this area, between the fourth century B.C. and the early Middle Ages, with energy able to damage and produce collapse in some temples of Selinunte. In this framework, we propose the use of non-invasive approaches in geoarchaeology for det…

Integration of HVSR measures and stratigraphic constraints for seismic microzonation studies: the case of Oliveri (ME)

Abstract. Because of its high seismic hazard the urban area of Oliveri has been subject of first level seismic microzonation. The town develops on a large coastal plain made of mixed fluvial/marine sediments, overlapping a complexly deformed substrate. In order to identify points on the area probably suffering relevant site effects and define a preliminary Vs subsurface model for the first level of microzonation, we performed 23 HVSR measurements. A clustering technique of continuous signals has been used to optimize the calculation of the HVSR curves. 42 reliable peaks of the H/V spectra in the frequency range 0.6–10 Hz have been identified. A second clustering technique has been applied t…

Diagnostic Multidisciplinary Investigations for Cultural Heritage at Etna Volcano: A Case Study from the 1669 Eruption in the Mother Church at the Old Settlement of Misterbianco

Misterbianco is located on the southern flank of Mt. Etna (Unesco site), in eastern Sicily (Italy). This site, also known as Monasterium Album, has a long and tormented history linked with volcanic activity of Mt. Etna and regional seismicity. This site received much attention in the 2000s when excavation works brought to light a 14th century church remains below the thick layer of the 1669 lava. This study documents the first diagnostic multidisciplinary survey performed at this site 350 years after the eruption: the investigations were performed by using techniques such as ground-penetrating radar, infrared thermography, a terrestrial laser scanner and a drone survey to analyze the site’s…

Seismostratigraphic modeling using constrained HVSR Data

An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of reconstruction of the buried geological setting where stratigraphic constraints are available. Specifically, the reconstruction of the stratigraphy in the studied area has been obtained by a seismic-stratigraphic three-dimensional modeling. This allowed for geophysical and geognostic data derived from surveys carried out during this study, as well as previously by the municipality of Palermo.

Physical identification of precious artefacts: their sonic imprint

Comparison of different acquisition patterns for 2D tomographic resistivity surveys

A systematic comparison is presented between some 2D resistivity models and their images by the inversion of synthetic datasets relating to three different arrays, suitable for multichannel data acquisitions (dipole-dipole (DD), Wenner-Schlumberger (WS) and multiple gradient (MG)). The goal is to study how the measurement errors affects the resolution of the tomographic models and the ability to retrieve correct information on buried targets. We considered different data acquisition patterns, gradually increasing the complexity of the combinations of potential spacing and dipolar distance. To this end we increased the number of current dipoles to obtain approximately the same amount of meas…

A Lightweight Prototype of a Magnetometric System for Unmanned Aerial Vehicles

Detection of the Earth’s magnetic field anomalies is the basis of many types of studies in the field of earth sciences and archaeology. These surveys require different ways to carry out the measures but they have in common that they can be very tiring or expensive. There are now several lightweight commercially available magnetic sensors that allow light-UAVs to be equipped to perform airborne measurements for a wide range of scenarios. In this work, the realization and functioning of an airborne magnetometer prototype were presented and discussed. Tests and measures for the validation of the experimental setup for some applications were reported. The flight sessions, appropriately programm…

Integrated geochemical and geophysical surveys for a study of sea-water intrusion

Recenti interventi geofisici e microgeofisici per lo studio dei BB.CC.

Drones - New technologies for geophysics?

Drones, also referred as Unmanned Aircraft Systems (UAS), Unmanned Aerial Vehicles (UAV) or Remotely Piloted Aircraft (RPA), are aircraft without pilot on board. USA is today the leading country in the field of UAS but recently, seven European countries have pledged to launch joint programs for drones, with the aim of producing the next generation of UAS before 2020. According to some studies on the potential market of UAS in Europe, the geoscience sector is definitely one of the most promising. In this paper, we bring a short description and classification of drones, according to their sized and shaped, with particular attention to the advantages and drawbacks of each type in reference to …

Geophysical and geotechnical investigations to support the restoration project of the Roman ‘Villa del Casale’, Piazza Armerina, Sicily, Italy

A multidisciplinary geophysical and geotechnical study, including some non-invasive geophysical applications, was carried out during the restoration of the ‘Villa del Casale’, a Roman villa discovered near Piazza Armerina (Sicily, Italy) in 1929, famous for its Roman floor mosaics. The project aims were to characterize the geology of the subsoil and provide information for solving the main building structural problems including the subsidence of some parts of the floor and the detachment of the tesserae (i.e., the tiles) of the mosaics. Another goal was the detailed study of the underground structures of the Corridor of the Great Hunt, a part of the villa strongly affected by subsidence and…

Integrated Geophysical Investigations at the Greek Kamarina Site (Southern Sicily, Italy)

Kamarina, located in southern Sicily (Italy), was an important Greek colony since its foundation in the sixth century BC. Archaeological excavations, carried out since the twentieth century, uncovered only limited portions of the site so far. Despite the importance of the Greek colony, the presence of remarkable buildings that archaeologists expected to bring to light has not found fully correspondence in the archaeological excavations. Consequently, the integrated geophysical prospection carried out in the study area is aimed to support and address the future archaeological investigations. After the photographic and thermographic survey obtained by an unmanned aerial vehicle, we performed …

Joint interpretation of electrical and seismic data aimed at modelling the foundation soils of the Maredolce monumental complex in Palermo (Italy)

The monumental complex of Maredolce (Palermo) includes an Arab-Norman castle that stands on the banks of an artificial lake carved out of the calcarenitic rock that rests on impermeable clays. The lake was originally filled with water, thanks to the channelling of a spring. Over time, the lowering of the water table and the high hydraulic permeability of the calcarenites have caused the lake to dry up. A project to renovate the monumental complex has recently been launched. It also provides the study of a possible restoration of the original conditions of the lake. To this end, a multidisciplinary geophysical study was carried out to investigate the geotechnical conditions of permeability o…

Geophysical investigations in the Flumendosa River Delta, Sardinia (Italy) — Seismic reflection imaging

A geophysical investigation that included seismic-reflection surveying and time-domain electromagnetics (EM) was carried out in the Flumendosa River Delta plain in southeastern Sardinia, Italy. The objective was to improve knowledge of geologic and hydrogeologic controls on a highly productive aquifer hosted in thick Quaternary deposits and known to be affected by an extensive saltwater intrusion. The seismic reflection survey, whose results are reported here, aimed to image the Paleozoic bedrock topography and to obtain detailed structural and stratigraphic information on the sequence of largely fluvial sediments extending from the surface down to bedrock. The survey consisted of two inli…

Cluster analysis of HVSR peak datasets to detect geological structures

A modified centroid-based algorithm has been applied to HVSR (Horizontal to Vertical Spectral Ratio) datasets (Nakamura, 2000) acquired for studies of seismic microzoning in various urban centers of Sicilian towns also aimed to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al. 2014). HVSR data were previously properly processed to extract frequency and amplitude of peaks by a code based on clustering of HVSR curves determined in sliding time windows. In centroid-based clustering, clusters are represented by a central vector, which may not necessarily be a member of the data set. After fixing the number of clusters, the algorithm find the cluster centers an…

Improvement of HVSR technique by cluster analysis

Implementation to Back-Projection Techniques of Resistivity Data

In order to obtain well contrasted images by back-projection of resistivity data some modifications to the back-projection algorithm as well as the use of filtering techniques for the sensitivity matrix were proposed (Kotre 1994; Cosentino et al. 1998). To further improve the back-projection algorithm a new implementation is here suggested. Besides a subsequent filtering algorithm of the sensitivity coefficient matrix is proposed. It is aimed to increase resistivity contrasts and to reduce smoothness in tomographic final representation. Finally the proposed technique is tested on synthetic data.

An approach to the electrical tomography aimed to the investigation of particular confined structures

In this paper we present a practical approach to the electrical tomography when applied to materials having particular shapes (like the columns). Simple cylindrical shapes have been tested, and the general model has been selected as a set of elements having circular sections of some angle and thickness.

Seismo-stratigraphic model of “La Bandita” area in the Palermo Plain (Sicily, Italy) through HVSR inversion constrained by stratigraphic data

Ambient noise Horizontal-to-Vertical Spectral Ratio (HVSR) technique is commonly used approach to obtain 1D models of the shear-wave velocity in the shallow surface of an investigated area. However, obtained models can have a wide margin of uncertainty if inversions have not been appropriately constrained by detailed stratigraphic information. An application of HVSR inversion constrained by lithostratigraphic data is presented in order to verify the effectiveness of this technique for purposes of geological and geophysical reconstruction of a sedimentary basin in a densely urbanized area. This is often the case of seismic microzonation studies, in which almost all the information derives fr…

Metodologie di microgeofisica per lo studio ed il monitoraggio di manufatti artistici ed ingegneristici

Dopo una breve introduzione sul significato e sulla crescita storica della Microgeofisica, il lavoro è focalizzato su alcune tecniche tomografiche, sviluppate ed implementate dal nostro gruppo di ricerca, che vengono utilizzate prevalentemente (ma non solo) per lo studio ed il monitoraggio dei manufatti di ingegneria edile e per i Beni Culturali costituiti da materiali lapidei, metallici, legnosi, ecc. In particolare, vengono presentate le seguenti tecniche, tutte caratterizzate dalla non invasività, dalla possibilità di applicazione in situ con strumentazione portatile, da una generale speditività applicativa rispetto a tecniche precedenti. 1. La tomografia sonica, ultrasonica (US) ed elet…

Resolution in wave-field tomographic approach

Non-invasive Geophysical Surveys in Search of the Roman Temple of Augustus Under the Cathedral of Tarragona (Catalonia, Spain): A Case Study

An integrated geophysical survey has been conducted at the Tarragona’s Cathedral (Catalonia, NE Spain) with the aim to confirm the potential occurrence of archaeological remains of the Roman Temple dedicated to the Emperor Augustus. Many hypotheses have been proposed about its possible location, the last ones regarding the inner part of the Cathedral, which is one of the most renowned temples of Spain (twelfth century) evolving from Romanesque to Gothic styles. A geophysical project including electrical resistivity tomography (ERT) and ground probing radar (GPR) was planned over 1 year considering the administrative and logistic difficulties of such a project inside a cathedral of religious…

Comparison of different sets of array configurations for multichannel 2D ERT acquisition

Abstract Traditional electrode arrays such Wenner-Schlumberger or dipole-dipole are still widely used thanks to their well-known properties but the array configurations are generally not optimized for multi-channel resistivity measures. Synthetic datasets relating to four different arrays, dipole-dipole (DD), pole-dipole (PD), Wenner-Schlumberger (WS) and a modified version of multiple gradient (MG), have been made for a systematic comparison between 2D resistivity models and their inverted images. Different sets of array configurations generated from simple combinations of geometric parameters (potential dipole lengths and dipole separation factors) were tested with synthetic and field dat…

Indagini microgeofisiche integrate sulla statua di Venere Anadiomene (II Sec. A.C.)

Misure microgeofisiche sulla statua del S. Michele Arcangelo (scuola Gaginiana, XVI sec.)

Comparative tests of some multi-electrodic arrays using models of particular interest in engineering and environmental geophysics

Application of non-invasive seismic techniques for the characterisation of a gravity concrete dam

The use of non-invasive investigation methods is becoming frequent as a support for the monitoring of water reservoirs and for the management of dam safety. In this context, geophysical techniques are much less invasive than geotechnical tests and allow to obtain two-dimensional or three-dimensional representations of the mechanical parameters of an engineering structure. A case of application of constrained inversion and joint interpretations of non-invasive seismic techniques is discussed, in order to monitor the Dirillo gravity concrete dam, in Sicily. To investigate the foundation soil, a stratigraphic borehole and a vertical seismic profile, carried out in the same hole, were used to c…

Caratterizzazione e monitoraggio di acquiferi costieri: Studio di un sito ad elevata vulnerabilità all'intrusione marina

Geophysical contribution to the reconstruction of the hydrological model of "Barcellona-Milazzo plain" groundwater body, northen Sicily

The “Barcellona-Milazzo plain” groundwater body in the northen Sicily, was analysed in detail, through numerous geophysical measurements that were integrated with stratigraphic data in order to reconstruct the hydrological model. The “Barcellona-Milazzo plain” (BMP) groundwater body has been identified within the coastal sector between the village of Oliveri, to the west, and Capo Rasocolmo, to the east. It also includes several rivers that rise further south in correspondence with the Peloritani ridge and flow into the wide Barcellona-Milazzo alluvial plain. On the basis of several geophysical and geological data analysis and interpretation have been used to reconstruct the composition and…

A Low Cost Customizable Micro-ROV for Environmental Research - Applications, Advances and Challenges

Summary Several shallow submarines areas are characterized by considerable releases of hydrocarbon gases, which, during earthquakes or volcanic activity, may suddenly and violently occur. In some instances, changes in chemical and physical properties of gas emissions, which are generated by geothermal systems connected to the volcanoes’ plumbing system, are important precursors of volcanic activity and useful indices for the study of the geothermal field. Furthermore, some superficial structures such faults, landslide slopes or archaeological relics should be studied with such a high detail that geophysical and bathymetric surveys are unable to provide. In response to the needs increasingly…

Primi risultati delle indagini geofisiche nei siti archeologici di Mozia (Sicilia Occidentale) e Pollentia (Isola di Maiorca). Progetto FIRB 2003 – Ricostruzione e valorizzazione del paesaggio archeologico in ambiente costiero mediterraneo tramite tecnologie innovative non invasive

Indagini geofisiche in siti archeologici con mosaici: interventi sulla Villa del Casale, a Piazza Armerina

Joint interpretation of constrained electrical and seismic models to study the landslide affecting the Agrigento Cathedral

On the stationarity of the horizontal to vertical noise spectral ratio

The Horizontal to Vertical Noise Spectral Ratio (HVNSR) method is nowadays widely used to estimate the resonance frequencies of geological structures. In the HVNSR method, seismic noise is considered as a stationary stochastic process. However, especially in industrialized/urbanized area, this is a very strict assumption seldom occurred. Several sources of noise can generate non stationary and anisotropic microtremor fields. To investigate the stationarity of microtremor, we have carried out several long-term measures of seismic noise with broad-band seismic sensors, in areas where the main source of anthropogenic noise is well known. The signals acquired have been analyzed both in frequenc…

Identification of Precious Artefacts: The Sonic Imprint for Small Artefacts

Identification of artworks is mainly based on a few characteristics which can be observed using non-invasive tools (sight, touch, simple instruments), the investigated properties being geometry, weight, colours, texture, etc. Nowadays, technology allows reproducing all these characteristics to such an extent that even expert conservators can be deceived: in particular at the present time even the geometry of an artwork can be easily reproduced with the help of laser scanner analysis and with a rapid prototyping machine or a computer numerical control (CNC) milling machine. We propose a new tool, the Sonic Imprint, producing a code capable of identifying a rigid artefact from its vibrational…

2d GPR and geoelectrical modelling: tests on man–made tunnels and cavities

B036 2D GPR AND GEOELECTRICAL MODELLING: TESTS ON MAN–MADE TUNNELS AND CAVITIES Introduction 1 Many engineering and environmental projects require geophysical exploration to minimize the geological risk connected with the presence of natural or artificial tunnels and cavities (air and/or water filled). Many studies have been carried out to optimize the procedures to investigate these cavities using many geophysical methods (Beres et al. 2001; Li et al. 2004). In this paper we like to confirm the reliability of combined geophysical methodologies (GPR and ERT) and relative modelling to detect and locate cavities in a particular site (Marsala Western Sicily) where

3D ERT for the study of an ancient wall covered by precious mosaics

The DC electrical tomography (ERT) is still a method scarcely diffused for the study of masonry of recent and ancient buildings, in spite of the very high resolution power of this methodology. The major limitation on ERT applicability on precious surfaces (like masonries or floors with fresco or mosaic covering) depends on the method of current injection: usually it is necessary to drive electrodes (small nails) into small perforations on the surfaces, to obtain sufficiently high current values (to produce good signal to noise ratio). An interesting application of the MYG array (that reduces significantly, compared to other classical arrays, the number of electrodes utilized for current inj…

Metodi geofisici per la ricerca di cavità: caso di studio alle Cave di Marsala (TP)

Many engineering and environmental projects require geophysical exploration to minimize the geological risk connected with the presence of natural or artificial tunnels and cavities (air and/or water filled). In this paper we like to confirm the reliability of combined geophysical methodologies (GPR and ERT) and relative modelling to detect and locate cavities in a particular site (Marsala Western Sicily) where underground dug structures exist. These structures may be used as real artificial physical models, very useful for testing geophysical methodologies. These shallow sandstone caves have, in general, a rectangular shape and are interconnected by tunnels. Most of these structures can be…

The structure of a hydrothermal system from an integrated geochemical, geophysical and geological approach: the Ischia Island case study

The complexity of volcano-hosted hydrothermal systems is such that thorough characterisation requires extensive and interdisciplinary work. We use here an integrated multidisciplinary approach, combining geological investigations with hydrogeochemical and soil degassing prospecting, and resistivity surveys, to provide a comprehensive characterisation of the shallow structure of the south-western Ischia’s hydrothermal system. We show that the investigated area is characterised by a structural setting that, although very complex, can be schematised in three sectors, namely the extra caldera sector (ECS), caldera floor sector (CFS), and resurgent caldera sector (RCS). This contrasted structura…

Electrical resistivity and induced polarization tomographies to test the efficiency and safety of the new landfill of Bellolampo (Palermo, Italy)

A geophysical study by means of electrical resistivity and induced polarization tomographies was carried out in the landfill site of Bellolampo (Palermo, Italy) to check the integrity of the landfill liner and to detect possible leachate plumes. Preliminarily, synthetic tests were performed, simulating acquisition data along profiles placed above resistivity distribution, suitable to represent landfills protected with an high-density polyethylene (HDPE) liner at the bottom or with possible leachate plumes. Optimized array data sets for parallel measurements have been tested in order to assess the resolution and the effectiveness of tomographic images, comparing inversions with and without t…

New seismological and geological-structural contributions to the support of a seismotectonic model of the hinge area between northern Sicily and southern Tyrrhenian

Study And Monitoring Of Salt Water Intrusion In The Coastal Area Between Mazara Del Vallo And Marsala (South-Western Sicily)

In this chapter the study of a coastal aquifer located in South-Western Sicily (between the towns of Marsala and Mazara del Vallo) is presented, carried out using geochemical, hydro-geological and geophysical techniques. The aquifer has been over-exploited to the point of being subject to intense and worrisome salt-water intrusion. A preliminary chemical and physical characterization of the waters was carried out; this included measuring their conductivity and their chloride content. This allowed to detect the marine intrusion wedge in the coastal aquifer. A series of electromagnetic soundings, suitably calibrated by well logs, were effected in the whole area and allowed to create a 3D inte…

Valutazione di differenti quadripoli e sequenze di misura per tomografie elettriche in contesti industriali e costieri

Inverse problem for tripotential measures in the study of buried cavities

This paper presents a solution to the inverse electrical problem for the interpretation of apparent resistivity anomalies due to empty buried cavities of quasi-spherical shape when tripotential measures are carried out. The anomalies of the apparent resistivities ra,rb andrg,and the composed resistivitiesrmand rt were previously calculated for a sufficient class of spherical models of resistivity anomalies. Then, for the whole class of models, some functionals of spatial distribution of the apparent and composed resistivity were identified and analyzed. They represent the average characteristics of the anomalies and, depending in a simple way on the fundamental parameters of the sources of …

Confronto del potere risolvente di differenti configurazioni elettrodiche nella prospezione geoelettrica su modelli 2D

Contribution of the cluster analysis of HVSR data for near surface geological reconstruction

The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al. 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al. 2014) and to identify areas with similar seismic behaviour. Theoretical considerations (Nakamura 1989) and experimental tests showed that amplification of horizontal motions between bottom and top of a sedimentary cover is well related to the ratio between the spectra of the horizontal and vertical components of the ground velocity (Nakamura 2000). This ratio is a measure of ellipticity of Rayleigh wave polarization, overlooking Love and body waves contribution. Assuming that subsoil can be represented as a stack of homogeneous…

From Geophysics to Microgeophysics for Engineering and Cultural Heritage

The methodologies of microgeophysics have been derived from the geophysical ones, for the sake of solving specific diagnostic and/or monitoring problems regarding civil engineering and cultural heritage studies. Generally, the investigations are carried out using different 2D and 3D tomographic approaches as well as different energy sources: sonic and ultrasonic waves, electromagnetic (inductive and impulsive) sources, electric potential fields, and infrared emission. Many efforts have been made to modify instruments and procedures in order to improve the resolution of the surveys as well as to significantly reduce the time of the measurements without any loss of information. This last poin…

Integration of stratigraphic data with HVSR measures for studies of seismic microzonation: the case of Oliveri (ME)

The seismic microzoning is a technique of analysis of a territory which aims to recognize, at a small scale, the local geological and geomorphologic conditions that may significantly affect the characteristics of the seismic motion, generating stress on structures that could produce permanent and critical effects. In other words, this technique has the objective to predict and evaluate possible site effects as a result of an earthquake. The first phase of the seismic microzoning is the detailed partition of the territory in homogeneous areas with respect to the expected behavior of soils during an earthquake. The seismic micro-zoning is a tool for prevention and reduction of seismic risk pa…

Method of detecting a sonic imprint of a three dimensional object and related apparatus

Non invasive method used to detect a "sonic imprint" of three-dimensional objects, particularly suitable for the identification and monitoring of artworks, consisting in acquiring the vibrations caused by a source of elastic waves and using a set of detectors fixed in various predetermined points of the external surface of the object. An apparatus, cheap and simple to utilize, suitable to execute this method, is also described.

METHOD FOR DETECTING A SONIC IMPRINT OF A THREE-DIMENSIONAL OBJECT AND RELATED APPARATUS

Non invasive method used to detect a “sonic imprint” of three-dimensional objects, particularly suitable for the identification and monitoring of artworks, consisting in acquiring the vibrations caused by a source of elastic waves and using a set of detectors fixed in various predetermined points of the external surface of the object. An apparatus, cheap and simple to utilize, suitable to execute this method, is also described.

The Corridor of the great hunting scene, Villa del Casale (Piazza Armerina)

Geophysical investigations at the Himera archaeological site, northern Sicily

In this paper we present a geophysical survey that was carried out as a research activity during field trips to the Himera archaeological site, where relics of a large Greek settlement are still buried, effected by a joint group of archaeologists and geophysicists during an educational project. Two-dimensional (2D) resistivity and ground-penetrating radar (GPR) surveys were performed to locate buried archaeological structures at this archaeological site. The results of the GPR surveys show some anomalies characterized by semi-hyperbolic shapes. In some restricted areas of the town, two grids of parallel GPR profiles were acquired while time- and depth-slices were calculated to identify the …

La GTT, metodologia non invasiva per caratterizzare lo strato esterno degradato dei manufatti lapidei

In questo lavoro viene descritta una metodologia non invasiva ne, tanto meno, distruttiva per studiare il degrado degli strati superficiali dei manufatti lapidei, correlandolo ai parametri di resistenza meccanica. La metodologia adopera come strumento diagnostico la propagazione delle onde elastiche nel mezzo in esame. In particolare, considerando che l'ordine di grandezza degli spessori ricercati è compreso tra le frazioni di millimetro e pochi centimetri, le frequenze delle onde elastiche utilizzabili sono quelle ultrasoniche, dalle decine di kHz ai MHz (e quindi, con velocità di propagazione dell'ordine di 4000 m/s, con lunghezze d'onda dai centimetri alle frazioni di millimetro). Questa…

Seismic investigation for the characterization of a gravity concrete dam

Monitoring of large-scale infrastructures plays an important role for public safety and prevention. The control of the safety assessment of a dam is largely dependent on knowledge of the mechanical parameters of the actual construction, as well as its geological substratum. The application of geophysical methods can considerably contribute to the examination indicating the less consolidated material and the degradation of mechanical parameters. A seismic tomographic approach has been used in a typical gravity concrete dam without reinforcement to detect mechanical properties of the body of the dam and its geological setting. Three seismic travel time tomographies in the dam body as well as …

A contribution to a seismotectonic model of the hinge zone between northern Sicily and southern Tyrrhenian by some seismological and structural constraints

An integrated research on the hinge zone between northern Sicily and its Tyrrhenian off-shore has been carried out, by means of structural, seismological and statistical analyses. The main structural features of the area are represented by both NWSE to W–E striking right-lateral and N–S to NE-SW striking leftlateral fault systems, responsible of uplifting (restraining) and subsiding (releasing) zones. Within this hinge zone the seismicity is mainly located between 10 and 20 km of depth and clustered according to the orientation of the outcropping fault systems. The brittle strain partitioning related to a right-lateral simple shear zone has been reconstructed in the onshore sector, while in…

Virtual three-dimensional model of the subsoil of the church of St. Maria Maddalena d'Alga in Palermo, using high-resolution GPR surveys

The church of Santa Maria Maddalena d'Alga is located in the historic center of Palermo and belongs to the monumental complex of the military district of San Giacomo, in the ancient western fortified area of the city. Today the area hosts a vast military complex, seat of the Command of the Carabinieri Legion of Sicily. The church is elevated with respect to the current floor. During some maintenance works of the church, for the installation of air conditioners, some georadar surveys were carried out to verify the presence of crypts or tombs under the pavement. The investigations made it possible to reconstruct a 3D georadar model and to identify some anomalies under the pavement. Some of th…

Diagnostica per il consolidamento del mosaico pavimentale dell’ambulacro nella villa romana del casale (Piazza Armerina)

Near surface seismostratigraphic modelling of the Bandita plain in Palermo town (Italy) from integra-ted analysis of HVSR and stratigraphic data

The Horizontal to Vertical Spectral Ratio (HVSR) noise method (Nakamura, 1989) is nowadays widely used to estimate the resonance frequencies of geological structures (Bonnefoy-Claudet, 2006). However, often HVSR is also used to obtain information on the depth of the seismic bedrock and on thickness and seismic velocity of the process overburden deposits, using inversion techniques of the H/V curve (Fäh et al., 2003). This nevertheless produce results with large uncertainty intervals of parameters, and then must be necessarily constrained by detailed stratigraphic information. An application of HVSR inversion is presented in order to verify the effectiveness of this technique for purposes of…

Analysis of HVSR Data Using a Modified Centroid-Based Algorithm for Near-Surface Geological Reconstruction

Recently, the use of microtremor techniques for subsoil investigation has increased significantly. The HVSR (Horizontal to Vertical Spectral Ratio) technique allows, in many cases, to obtain a seismo-stratigraphic reconstruction of the subsoil and to identify areas with similar seismic behavior. However, the stratigraphic interpretation of the HVSR peaks still remains a subjective choice and linked to a priori information. A non-hierarchical centroid-based algorithm was modified to group HVSR peaks of different measurements that can be attributed to the same generating seismic discontinuity. Some tests performed have shown that the proposed algorithm produces valid results even in the absen…

Multidisciplinary investigations at the Kamarina archaeological site (southern Sicily, Italy)

Multidisciplinary geophysical investigations have been carried out in a small area of the Greek archaeological site of Kamarina, in southern Sicily, in order to support some hypotheses, derived from historical and archaeological bases. After an aerial photographic and thermographic survey, a small area near to the Agora has been considered for magnetometric and GPR investigations. Obtained results show a good correlation and allow to highlight some structures oriented in agreement with the uncovered remains. The use of integrated geophysical techniques allowed a more robust interpretation of the detected anomalies in order to better address the choices for new excavations.

Geophysical study of an landslide in northern Sicily

The San Fratello area in the Nebrodi Mountains (northern Sicily) is a region of high instability. It has suffered many devastating occurrences, which have hit and destroyed the village of San Fratello. At present the area is still subject to a high landslide risk. A series of geophysical surveys have been carried out with the aim of determining the thickness and dimensions of the landslide body as well as some tectonic features, in order to gain insight into the evolution of the landslide. The following geophysical techniques have been used: borehole seismic tomography, i.e. down-hole tomographic seismic soundings (DH TSS), time-domain electromagnetic (TDEM) soundings and georadar profiling…

Coseismic Damage at an Archaeological Site in Sicily, Italy: Evidence of Roman Age Earthquake Surface Faulting

Archaeoseismology can provide a useful chronological tool for constraining earthquakes and documenting significant evidence that would otherwise be lost. In this paper, we report a case of surface faulting on ancient man-made structures belonging to the archaeological site of Santa Venera al Pozzo situated along the eastern flank of Mt. Etna volcano in eastern Sicily (southern Italy), which is affected by well-developed tectonic faults. Geological surveys highlight a set of fractures affecting the archaeological ruins, suggesting the occurrence of a capable fault zone across the area. An integrated geophysical survey was carried out in order to identify the main subsurface tectonic disconti…

Integrated interpretation of geophysical surveys aimed at tridimensional modeling of a coastal aquifer subjected to sea-water intrusion

Quattro esempi di applicazioni geofisiche per l'archeologia a scala medio-piccola

Importance of geological information for geophysical modelling

Archaeological excavation confirms the geophysical anomalies recorded at the cathedral of tarragona - A comparative study

An integrated geophysical survey was conducted in September 2007 at the Cathedral of Tarragona to search for archaeological remains of the Roman temple dedicated to the Emperor Augustus. Many hypotheses about its location have been put forward, the most recent ones suggesting it could be inside the present cathedral. A project including Electrical resistivity tomography (ERT) and Ground probing radar (GPR) was planned for a year and conducted during a week of intensive field survey. Both ERT and GPR provided detailed information about subsoil structures. Different ERT techniques and arrays were used, ranging from standard Wenner-Schlumberger 2D sections to full 3D electrical imaging using t…

Misure geofisiche utili al progetto di restauro

Investigation of cavity artificial models using 2D GPR and electrical data

Integrated geophysical survey in the archaeological site of Himera (Northern Sicily)

Joint Investigation with Ground Penetrating Radar and Infrared Thermography as a Diagnostic Support for the Restoration of Two Wall Mosaics in the Church of St. Mary of the Admiral in Palermo, Italy

The church of S. Mary of the Admiral in Palermo, known as “La Martorana” and very famous for its Byzantine mosaics, has been a World Heritage site since 2015. The mosaic system of the church includes several groups of figures and scenes from the life of the Virgin Mary. From the western part of the ancient church only two mosaics survive, detached from their original position, and are now located in two internal chapels. On the occasion of several restoration works, these two mosaic panels were investigated with non-invasive techniques, in order to provide diagnostic support to the restoration and consolidation interventions. The investigations were aimed at detecting any air po…

Recognition of earthquake-induced damage in the Abakainon necropolis (NE Sicily): results from geo-morphological, geophysical and numerical analyses

Seismotectonic activity and slope instability are a permanent threat in the archaeological site of Abakainon and in the nearby village of Tripi in NE Sicily. In recent times, signs of an ancient earthquake have been identified in the necropolis of Abakainon which dating was ascertained to the first century AD earthquake. The site is located on a slope of Peloritani Mts. along the Tindari Fault Line and contains evidence for earthquake-induced landslide, including fallen columns and blocks, horizontal shift and counter slope tilting of the tomb basements. In this paper, we used an integrated geomorphological and geophysical analysis to constrain the landslide. The research was directed to th…

Selection of time windows in the horizontal-to-vertical noise spectral ratio by means of cluster analysis

The selection of the elementary analysis windows in continuous noise recordings for optimal estimation of the mean horizontal‐to‐vertical spectral ratio (HVSR) curve is generally performed by visual inspection of HVSR curves considered as functions of time. Starting from full‐length records, HVSR curves are determined in consecutive time windows of appropriate lengths. Time windows with HVSR curves that are anomalous on the basis of a simple visual inspection are generally ignored in the computation of the average HVSR curve. It is often very difficult to optimize the selection of time windows to be used for the calculation of the HVSR curve representative of a site. The use of nonobjective…

Joint interpretation of seismic refraction tomography and electrical resistivity tomography by cluster analysis to detect buried cavities

Abstract In the last few years, the geophysical methods of seismic refraction tomography (SRT) and electrical resistivity tomography (ERT) are among the most used geophysical techniques for the reconstruction of subsoil geometries, for the investigation of underground cavities and also for the archaeological prospecting. However, the main disadvantage of each geophysical method is the difficulty of final interpretation of the data. In order to eliminate artifacts and generally improve the reliability and accuracy of geophysical interpretation, it is useful to perform a joint approach of different geophysical methods, also introducing the a priori information. In this work, it is shown the i…

Indagini geofisiche a supporto dell’intervento di restauro di Palazzo Branciforte (Palermo)

Integrated use of unmanned aerial vehicle photogrammetry and terrestrial laser scanning to support archaeological analysis: The Acropolis of Selinunte case (Sicily, Italy)

Southwestern Sicily is an area of infrequent seismic activity; however, some studies carried out in the archaeological Selinunte site suggest that, between the fourth century BC and the early Middle Ages, probably at least two earthquakes strucked this area with enough energy to damage and cause the collapse and kinematics of much of the architecture of Selinunte. Take into account that, in 2008, a noninvasive archaeological prospection and traditional data gathering methods along the Acropolis north fortifications were carried out. Following these first studies, after about 10 years, a new geophysical campaign was carried out. This second campaign benefited from the application of modern t…

Assessment of the Reliability of the SPAC Method in Urban Areas

We have carried out several long-term measures of seismic noise with triangular arrays of broad-band seismic sensors, to investigate the reliability of the SPAC method in urban areas. We investigate the stationary and anisotropy of the microtremor wave field. We have found that the anisotropy of the microtremor wave field can be evaluated analyzing the HVNSR as function the azimuth. Furthermore, we showed as strong anisotropies in the microtremors are often observable in particular at high frequencies (> 1 Hz). We have verified as microtremors can be difficult to considered as ergodic processes, and for this reason time averaging, also even over a long periods of time, cannot replace an app…

Advances in microgeophysics for engineering and cultural heritage

A large number of unconventional investigations have been implemented, tested, and validated in the field of microgeophysics, with the aim being to solve specific diagnostic and/or monitoring problems regarding civil engineering and cultural heritage studies. The investigations were carried out using different tomographic 2D and 3D approaches as well as different energy sources, namely sonic, ultrasonic and electromagnetic (radar) waves, electric potential fields, and infrared thermography. Many efforts have been made to modify instruments and procedures in order to improve the resolution of the surveys as well as to greatly reduce the time of the measurements without any loss of informatio…

New Data from Pleistocene deposit of S. Ciro cave

Quaternary fossil sites in Sicily have been known for a long time and all of them have a common story of human predation and manipulation. Hence, we illustrate the first electrical tomography applied to the study of a fossiliferous deposit in a cave in Sicily. The site investigated is the deposit inside the cave of San Ciro-Maredolce, near Palermo. This study aims to answer the following questions: is the geoelectric survey applicable to quaternary deposit of caves? is the deposit still existing or has been completely emptied? Here we show a ERT model (Electrical Resistivy Tomography) of deposit and possible anthropogenic interactions (presence of historic and\or illegal excavations) with t…

Metodo di rilevamento di una impronta sonica di un oggetto tridimensionale e relativo apparato

Cluster analysis for cavity detection using seismic refraction and electrical resistivity tomography

Geophysical methods (in particular ERT technique) constitute an excellent tool for the detection of buried cavities. However the integration approach of e different geophysical methods could minimize the ambiguity of geophysical interpretation of the buried cavity. The technique of electrical tomography has been joined to the technique of seismic refraction tomography in order to obtain more robust interpretations. Many tests have been carried out using synthetic data and experimental ones. It was finally used a statistical approach based on cluster analysis of the P-wave velocity, the density of the seismic rays and the electrical resistivity of the synthetic and experimental models. Distr…

Identification of Precious Artefacts and Stones: The sonic Imprint

Physical identification of precious artefacts: the sonic fingerprint