Introduction. An accurate reflection picking, as independent as possible from the subjectivity of... more Introduction. An accurate reflection picking, as independent as possible from the subjectivity of the interpreter, is of paramount importance when performing both qualitative (e.g. stratigraphic interpretation) and quantitative (e.g. amplitude inversion) analyses of several wave-field geophysical surveys. Automated picking processes can be used to facilitate interpretation and to recover several parameters and attributes (Chopra and Marfurt, 2005) from the recorded profile, most importantly the reflected amplitudes and the two-way traveltimes, which can then be used to estimate the main impedance contrasts in the subsurface. In ground penetrating radar (GPR) surveys, examples of application include the identification of contaminants in near-surface hydrogeological settings (Backer, 1998; Babcock and Bradford, 2013); the inspection and maintenance of roads through the identification of damaged sections (Saarenketo and Scullion, 2000); and the monitoring of glaciers in terms of their temporal variations in stratigraphy and water content (Forte et al., 2014a, 2014b; Colucci et al., 2015). In seismic surveys, an accurate picking can be used for first-breaks detection and data processing (Sabbione and Velis, 2010); amplitude-versus-offset analysis (AVO; Castagna and Backus, 2007); and the identification of faults in a profile, which are characterized by discontinuities in the picked events (Hoyes and Cheret, 2011). Several picking techniques exist (Dorn, 1998), and they differ in terms of 1) their adopted picking criteria, like for example manual picking, amplitude cross-correlation, or interpolation between control points (seeds); 2) the assumptions made with regards to the analyzed data set, for example that the recorded events are locally smooth; 3) the accuracy of the picked results and their dependence on the interpreter's subjectivity and experience. We developed an automated process designed to accurately detect, and mark as a horizon, any event that shows lateral phase continuity, and to select specific reflection phases for subsequent analysis and interpretation. In this paper, we give a short description of the main features of the implemented algorithm (more details in Dossi et al., 2015a, b; Forte et al., 2015), and show a few examples of its application to both GPR and seismic data sets. Automated picking. The algorithm starts by performing attribute analysis on the recorded data set, also known as complex trace analysis (Taner et al., 1979; Barnes, 1996, 2007), separating the signal into its reflection strength (also referred to as instantaneous amplitude, or trace envelope) and the cosine of its instantaneous phase (also referred to as cosine phase). The cosine phase profile allows to follow reflections more accurately with respect to the
Introduction. In this work we present three examples of application of Ground Penetrating Radar (... more Introduction. In this work we present three examples of application of Ground Penetrating Radar (GPR) method for pavement thickness evaluation and stratigraphic analysis using R.Ex. (Road Explorer), a new system developed by Esplora srl, an academic spin-off of the University of Trieste, in collaboration with the geophysical group of the Department of Mathematics and Geosciences of the same University. The implementation of this GPR system aims to obtain information that are crucial for the good management and planning of road maintenance, which is fundamental to prevent and minimize the risks to which light and heavy vehicles may be exposed during transit, and ensure the maximum safety for passengers. Nowadays, for testing of pavement of new road infrastructures, direct measurements such as drill cores are performed. Usually drillings reach a depth of about one meter from the road surface and its lateral spacing is variable, basing on the importance of the road and its constructive...
Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in te... more Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of their clear identification and mapping considering the rehash and man-made structures. In the present research, we have proposed and tested a methodology to identify the subsiding features through an integrated and non-invasive multi-scale approach combining seismic reflection, PS-InSAR (PSI), leveling and full 3D Ground Penetrating Radar (GPR), and thus overpassing the limits of each method. The analysis was conducted in a small village in the Alta Val Tagliamento Valley (Friuli Venezia Giulia region, NE Italy). Here, sinkholes have been reported for a long time as well as the hazards linked to their presence. Within past years, several houses have been demolished and at present many of them are damaged. The PSI investigation allowed the identification of an area with higher vertical velocities; seismic reflection imagined the covered karst bedrock, identifying three depocenters;...
The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor ... more The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming. The Eurasian Ice Sheet Complex during the Last Glacial Maximum (LGM, 21 ky BP) comprised three large ice sheets: the British-Irish Ice Sheet, the Fennoscandian Ice Sheet and the Barents Sea Ice Sheet 1. In particular, the Barents Sea Ice Sheet was largely marine based, as its largest portion rested hundreds of meters below sea level on the Barents Sea floor. The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet 2. At the LGM the ice stream extended up to the continental shelf edge in the western Barents Sea 3 (Fig. 1). Sediment cores from the outer shelf in the southwestern Barents Sea suggest that the Bjørnøyrenna Ice Stream started to retreat from the outer shelf to the inner part of Bjørnøyrenna between 17.1-16.1 ky BP 4 , (Fig. 1). Geological data show that the ice Stream had northern and eastern tributaries extending into the central Barents Sea, sourced from Storbanken/Storbankrenna and Sentralbankrenna/Sentralbanken respectively. Dates from glacimarine sediments suggest that the deglaciation of Sentraldjupet to the east of Bjørnøyrenna started between 15.2-14.8 ky BP 5 , and that ice-free conditions prevailed after 11.3-10.9 ky BP 6 (Fig. 1). Due to similar morphological and glaciological features, the Bjørnøyrenna Ice Stream is acknowledged as an analogue for several present-day ice streams in the West Antarctic Ice Sheet (WAIS) 7. Therefore, it is interesting to identify the dynamic processes driving the retreat of the Bjørnøyrenna Ice Stream over the western Barents Sea continental shelf during the last deglaciation. Here, we focus on the role exerted by the sub-shelf melting and by grounding-line dynamics as triggers of the ice stream retreat. Several recent studies show that ice shelves and
Sinkholes are a well-known geologic hazard but their past occurrence, useful for subsidence risk ... more Sinkholes are a well-known geologic hazard but their past occurrence, useful for subsidence risk prediction, is difficult to define, especially for ancient historic times. Consequently, our knowledge about Holocene carbonate landscapes is often limited. A multidisciplinary study of Trieste Karst (Italy), close to early Roman military fortifications, led to the identification of possible ancient road tracks, cut by at least one sinkhole. Electrical Resistivity Tomography through the sinkhole has suggested the presence of a cave below its bottom, possibly responsible of the sinkhole formation, while Ground Penetrating Radar has detected no tectonic disturbances underneath the tracks. Additionally, archaeological surveys led to the discovery of over 200 Roman shoe hobnails within or close to the investigated route. According to these data, the tracks are interpreted as the remains of a main Roman road, whose itinerary has been reconstructed for more than 4 km together with other elemen...
The damage and the eventual breach of river embankments may be due to internal erosion and instab... more The damage and the eventual breach of river embankments may be due to internal erosion and instability processes in the waterside and landside slopes. Beside the progressive degradation of soil properties, different types of macro-pores inside the levee body can influence its short-and long-term performance. Among macropores, burrows are a widespread form of biologic erosion of earthen structures potentially producing damage or even their collapse. In fact, animal burrows are erosion tunnels, which can lead to piping phenomena. Thus, the emergent risk connected to burrowing animals in earthen levees has to be tackled, given also the environmental changes driven by human activity and climate. Remote sensing and geophysical surveys can complement data from in situ investigation campaigns in the definition of the real-embankment model, as well as in the imaging of local defects which may influence its local and/or global stability. Several techniques were integrated in the study area of the Panaro River, where an active animal burrow was detected in spring 2015. Two campaigns were carried out: Survey-1, in June 2015, just after the relocation of the animals, and Survey-2 in December 2015, after the filling of the burrow with a cement-bentonite slurry. Here, we highlight the peculiarity of each method and the choice of an integrated multi-technique approach. The results allowed the known burrow, as well as two other tunnels, to be imaged in 3D, providing specific guidelines for the best integrated strategy to detect and characterize these macro-pores in a fluvial levee. The proposed approach can advance our knowledge of embankments in space and time, so that effective remedial actions in flood risk and wildlife management can be identified.
The southeastern European Alps represent the spot where mean annual precipitation is at its highe... more The southeastern European Alps represent the spot where mean annual precipitation is at its highest in the entire Alpine chain. Accordingly, the glacial evolution here might have a different spatial and chronological pattern if compared with other alpine areas. This paper discusses geomorphological evidence of three glacial stages from the Krnica Valley in the Julian Alps of Slovenia, and is the first step towards a comprehensive palaeoglaciological studies in this alpine sector. Very well-preserved glacial landforms in the Upper Krnica Valley allowed the reconstruction of glacier surface topographies and corresponding equilibrium line altitudes (ELAs) by means of field-based geomorphological and sedimentological data and by using geospatial analysis. The uppermost frontal moraines belong to the Little Ice Age (LIA) and the corresponding ELA is estimated at 1973 m a.s.l. Other two stages with the ELA depressed by 50 m and 161 m compared to the LIA ELA, suggest early Holocene and Younger Dryas ages of the palaeoglaciers, respectively. This assumption ensues from absolute age datings and related ELA depressions observed elsewhere in the European Alps. The presence of buried ice under the debris in the Krnica cirque, imaged through geophysical investigations, point to peculiar microclimatic conditions able to preserve relict glacier ice. This is favoured by the recursive presence of snow on the ground caused by the extreme summer shading and the significant winter snow-recharge triggered by snowblow and avalanche feeding. The possible evolution of such relict ice under the ongoing climate warming is also discussed.
The primary objective of this study is to evaluate the applicability and the effectiveness of gro... more The primary objective of this study is to evaluate the applicability and the effectiveness of ground-penetrating radar (GPR) to identify a thin burnt soil layer, buried more than 2 m below the topographic surface at the Liangzhu Site, in Southeastern China. The site was chosen for its relatively challenging conditions of GPR techniques due to electrical conductivity and to the presence of peach tree roots that produced scattering. We completed the data acquisition by using 100 and 200 MHz antennas in TE and TM broadside and cross-polarized configurations. In the data processing and interpretation phase, we used GPR attribute analysis, including instantaneous phase and geometrical attributes. Validation analysis ground-truthing performed after the geophysical surveys, validated the GPR imaging, confirmed the electrical conductivity and relative dielectric permittivity (RDP) measurements performed at different depths, and allowed a reliable quantitative correlation between GPR results and subsurface physical properties. The research demonstrates that multiple antenna configurations in GPR data acquisition combined with attribute analysis can enhance the ability to characterize prehistoric archaeological remains even in complex subsurface conditions.
We evaluate the applicability and the effectiveness of texture attribute analysis of 2-D and 3-D ... more We evaluate the applicability and the effectiveness of texture attribute analysis of 2-D and 3-D GPR datasets obtained in different archaeological environments. Textural attributes are successfully used in seismic stratigraphic studies for hydrocarbon exploration to improve the interpretation of complex subsurface structures. We use a gray-level co-occurrence matrix (GLCM) algorithm to compute second-order statistical measures of textural characteristics, such as contrast, energy, entropy, and homogeneity. Textural attributes provide specific information about the data, and can highlight characteristics as uniformity or complexity, which complement the interpretation of amplitude data and integrate the features extracted from conventional attributes. The results from three archaeological case studies demonstrate that the proposed texture analysis can enhance understanding of GPR data by providing clearer images of distribution, volume, and shape of potential archaeological targets and related stratigraphic units, particularly in combination with the conventional GPR attributes. Such strategy improves the interpretability of GPR data, and can be very helpful for archaeological excavation planning and, more generally, for buried cultural heritage assessment.
It is well known that small glaciers of mid latitudes and especially those located at low altitud... more It is well known that small glaciers of mid latitudes and especially those located at low altitude respond suddenly to climate changes both on local and global scale. For this reason their monitoring as well as evaluation of their extension and volume is essential. We present a ground penetrating radar (GPR) dataset acquired on September 23 and 24, 2013 on the Triglav glacier to identify layers with different characteristics (snow, firn, ice, debris) within the glacier and to define the extension and volume of the actual ice. Computing integrated and interpolated 3D using the whole GPR dataset, we estimate that at the moment of data acquisition the ice area was 3800 m 2 and the ice volume 7400 m 3. Its average thickness was 1.95 m while its maximum thickness was slightly more than 5 m. Here we compare the results with a previous GPR survey acquired in 2000. A critical review of the historical data to find the general trend and to forecast a possible evolution is also presented. Between 2000 and 2013, we observed relevant changes in the internal distribution of the different units (snow, firn, ice) and the ice volume reduced from about 35,000 m 3 to about 7400 m 3. Such result can be achieved only using multiple GPR surveys, which allow not only to assess the volume occupied by a glacial body, but also to image its internal structure and the actual ice volume. In fact, by applying one of the widely used empirical volume-area relations to infer the geometrical parameters of the glacier, a relevant underestimation of ice-loss would be achieved.
We evaluate the applicability and the effectiveness of GPR attribute analysis for high-resolution... more We evaluate the applicability and the effectiveness of GPR attribute analysis for high-resolution glacier imaging and characterization, testing this approach on 4-D GPR multifrequency data collected in a small glacier in the Eastern Alps, by repeating the acquisition along the same profiles in four different periods of the year 2013. The main objectives are to image and characterize the glacier's inner structure and to quantitatively monitor the seasonal thawing of near-surface frozen materials (snow/firn). A multiattribute approach is used to characterize the subsurface through different attribute categories, including instantaneous and textural attributes considering not only amplitude-, phase-and frequency-related attributes, but also other more complex and integrated parameters. We combine information from more than one attribute into a single image with composite displays, using overlays or mixed displays. The results demonstrate that the developed GPR attribute analysis can provide significant improvements in the discrimination of GPR signals, and obtain enhanced and more constrained data interpretations.
The Montasio Occidentale glacier is a 0.07 km2 wide, avalanche-fed glacier located at very low-al... more The Montasio Occidentale glacier is a 0.07 km2 wide, avalanche-fed glacier located at very low-altitude (1860- 2050 m a.s.l.) in the Eastern Italian Alps. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. Geometric changes and mass balance have been monitored starting in 2010, combining glaciological methods and high-resolution geodetic surveying with a terrestrial laser scanner (TLS). The TLS technique has proved to be very effective in determining the volume change of this glacier, but presents several limitations as high costs, high level of specialized training and low portability. On the other hand, the recent improvements in close-range photogrammetric techniques like the Structure from Motion (SfM), combined with dense image matching algorithms as Multi View Stereo (MVS), make them competitive for high quality 3D models production. The purpose of this work was to a...
The activation of Late Quaternary faults in the Central Apennines (Italy) could generate earthqua... more The activation of Late Quaternary faults in the Central Apennines (Italy) could generate earthquakes with magnitude of about 6.5, and the Monte Vettore fault system probably belongs to the same category of seismogenetic faults. Such structure has been defined 'silent', because of its geological and geomorphological evidences of past activation, but the absence of historical records in the seismic catalogues to be associated with its activation. The 'Piano di Castelluccio' intramountain basin, resulting from the Quaternary activity of normal faults, is characterized by a secondary fault strand highlighted by a NW-SE fault scarp: it has been already studied through palaeoseismological trenches, which highlighted evidences of Quaternary shallow faulting due to strong earthquakes, and through a 2-D ground penetrating radar (GPR) survey, showing the first geophysical signature of faulting for this site. Within the same place, a 3-D GPR volume over a 20 × 20 m area has been collected. The collection of radar echoes in three dimensions allows to map both the vertical and lateral continuity of shallow geometries of the fault zone (Fz), imaging features with high resolution, ranging from few metres to centimetres and therefore imaging also local variations at the microscale. Several geophysical markers of faulting, already highlighted on this site, have been taken as reference to plan the 3-D survey. In this paper, we provide the first 3-D subsurface imaging of an active shallow fault belonging to the Umbria-Marche Apennine highlighting the subsurface fault geometry and the stratigraphic sequence up to a depth of about 5 m. From our data, geophysical faulting signatures are clearly visible in three dimensions: diffraction hyperbolas, truncations of layers, local attenuated zones and varying dip of the layers have been detected within the Fz. The interpretation of the 3-D data set provided qualitative and quantitative geological information in addition to the fault location, like its geometry, boundaries and an estimation of the fault throw.
Proceedings of the National Academy of Sciences of the United States of America, Jan 16, 2015
An interdisciplinary study of the archaeological landscape of the Trieste area (northeastern Ital... more An interdisciplinary study of the archaeological landscape of the Trieste area (northeastern Italy), mainly based on airborne light detection and ranging (LiDAR), ground penetrating radar (GPR), and archaeological surveys, has led to the discovery of an early Roman fortification system, composed of a big central camp (San Rocco) flanked by two minor forts. The most ancient archaeological findings, including a Greco-Italic amphora rim produced in Latium or Campania, provide a relative chronology for the first installation of the structures between the end of the third century B.C. and the first decades of the second century B.C. whereas other materials, such as Lamboglia 2 amphorae and a military footwear hobnail (type D of Alesia), indicate that they maintained a strategic role at least up to the mid first century B.C. According to archaeological data and literary sources, the sites were probably established in connection with the Roman conquest of the Istria peninsula in 178-177 B....
SEG Technical Program Expanded Abstracts 2003, 2003
Multi-channel Analysis of Surface Waves (MASW) is a suitable technique for vertical shear-wave ve... more Multi-channel Analysis of Surface Waves (MASW) is a suitable technique for vertical shear-wave velocity profile determination whose efficiency and effectiveness depends on data acquisition parameters and processing procedures. In the present paper we compare the performances of three different methods to determine Rayleigh waves dispersion curves. Such curves are successively exploited for the inversion process, which eventually provides subsurface information of use in geological or geotechnical applications. We investigate the role of some processing procedures, with a special emphasis on the number of traces able to optimise the ratio between information content and acquisition and processing costs. We show that phase shift method is able to produce the best results in terms of accuracy and computation efficiency for the unconsolidated sediments considered in our work. Phase shift shows extremely stable results also when a reduced number of traces is considered and other methods fail due to spatial aliasing or severe noise content that prevents from unambiguous interpretation.
A 3D multi-fold GPR investigation was canied Out in the archaeological park of Aquileia in the fr... more A 3D multi-fold GPR investigation was canied Out in the archaeological park of Aquileia in the framework of a survey proposed by the local supenntendency of cultural heritage. Primary objective of the work was the identification of targets of potential archaeological interest in a polygon of approximately 2800 sqm in area, which borders the town cemetery to the north. The comparison of single-fold and multi-fold test profiles encouraged the design of a complete multi-fold grid. The 3-D option was chosen to correlate and map targets of limited dimensions. Targets of possible archaeological interest were identified at estimated depths not exceeding 200 cm in the part of the dataset processed to date. The comparison of single-fold and multi-fold 2-D and 3-D results shows an approximate 600% SNR enhancement for most of the observed targets with a net peak for a flat reflector which represents the major shallow discontinuity in the electric prop ei-ties of the soil and it is possibly associated with the base of the chaotic layer of recent deposition.. A large number of the interpreted targets was identified by means of the integrated interpretation of stack and prestack records, velocity analysis panels and 3-D data volumes.
We exploit a combination of transmission and reflection Ground Penetrating Radar (GPR) techniques... more We exploit a combination of transmission and reflection Ground Penetrating Radar (GPR) techniques to characterize limestone at different scales (from sub-metric/metric to decametric). The integrated method is based on Multi-Fold (MF) GPR techniques to obtain radar response at different offsets (source-receiver separation) corresponding to different incidence angles. MF GPR measurements are combined with transmission tomography where possible (isolated blocks). The MF datasets allow imaging of rock conditions, characterization of rock, fractures and filling materials. Imaging of joints, fractures, voids and heterogeneous volumes is performed by means of pre-stack and post-stack time and depth imaging methods. In this work experiments are carried out from the surface or on isolated blocks using a pulse GPR system equipped with 250, 500 and 800 MHz central frequencies antennas. The results show that the integrated multi-fold/tomographic method allows enhanced characterization of limestone, compared with conventional sonic methods and proves to be highly sensitive to subtle variations in the lithological and physical properties of the rock mass.
We use an integration of Single Fold (SF), Multi fold (MF), i.e. multi offset, Multi Azimuth (MA)... more We use an integration of Single Fold (SF), Multi fold (MF), i.e. multi offset, Multi Azimuth (MA) and Multi Component (MC) or Polarimetric Ground Penetrating Radar (GPR) configurations to identify, characterize and classify targets of environmental interest. The results obtained in real and controlled conditions are validated by numerical simulations and excavation and show that MF/MA/MC GPR methods are fit for target classification in complex subsurface conditions.
Surface wave dispersion has been shown to be a valuable tool for seismic investigation of subsurf... more Surface wave dispersion has been shown to be a valuable tool for seismic investigation of subsurface structures (Park et. al., 1999; Xia et al., 1999; Dal Moro et al., 2004). Dedicated inversion procedures are highly recommended, due to the complexity of the problem, but have been generally scarcely considered. The multi-modal and highly non-linear nature of surface wave dispersion curve inversion represents a prohibitive problem for common linear inversion procedures based on the Jacobian matrix because of failures due to local minima. Fig. 1 highlights such aspect through the data regarding a 6-layer synthetic model. Various V S and thickness values were adopted for the second and third layers while the values for the other layers were set to their proper values and the rms values (objective function, ObjFN) between the actual and calculated dispersion curves plotted versus the V S and thickness ratios.
Introduction. An accurate reflection picking, as independent as possible from the subjectivity of... more Introduction. An accurate reflection picking, as independent as possible from the subjectivity of the interpreter, is of paramount importance when performing both qualitative (e.g. stratigraphic interpretation) and quantitative (e.g. amplitude inversion) analyses of several wave-field geophysical surveys. Automated picking processes can be used to facilitate interpretation and to recover several parameters and attributes (Chopra and Marfurt, 2005) from the recorded profile, most importantly the reflected amplitudes and the two-way traveltimes, which can then be used to estimate the main impedance contrasts in the subsurface. In ground penetrating radar (GPR) surveys, examples of application include the identification of contaminants in near-surface hydrogeological settings (Backer, 1998; Babcock and Bradford, 2013); the inspection and maintenance of roads through the identification of damaged sections (Saarenketo and Scullion, 2000); and the monitoring of glaciers in terms of their temporal variations in stratigraphy and water content (Forte et al., 2014a, 2014b; Colucci et al., 2015). In seismic surveys, an accurate picking can be used for first-breaks detection and data processing (Sabbione and Velis, 2010); amplitude-versus-offset analysis (AVO; Castagna and Backus, 2007); and the identification of faults in a profile, which are characterized by discontinuities in the picked events (Hoyes and Cheret, 2011). Several picking techniques exist (Dorn, 1998), and they differ in terms of 1) their adopted picking criteria, like for example manual picking, amplitude cross-correlation, or interpolation between control points (seeds); 2) the assumptions made with regards to the analyzed data set, for example that the recorded events are locally smooth; 3) the accuracy of the picked results and their dependence on the interpreter's subjectivity and experience. We developed an automated process designed to accurately detect, and mark as a horizon, any event that shows lateral phase continuity, and to select specific reflection phases for subsequent analysis and interpretation. In this paper, we give a short description of the main features of the implemented algorithm (more details in Dossi et al., 2015a, b; Forte et al., 2015), and show a few examples of its application to both GPR and seismic data sets. Automated picking. The algorithm starts by performing attribute analysis on the recorded data set, also known as complex trace analysis (Taner et al., 1979; Barnes, 1996, 2007), separating the signal into its reflection strength (also referred to as instantaneous amplitude, or trace envelope) and the cosine of its instantaneous phase (also referred to as cosine phase). The cosine phase profile allows to follow reflections more accurately with respect to the
Introduction. In this work we present three examples of application of Ground Penetrating Radar (... more Introduction. In this work we present three examples of application of Ground Penetrating Radar (GPR) method for pavement thickness evaluation and stratigraphic analysis using R.Ex. (Road Explorer), a new system developed by Esplora srl, an academic spin-off of the University of Trieste, in collaboration with the geophysical group of the Department of Mathematics and Geosciences of the same University. The implementation of this GPR system aims to obtain information that are crucial for the good management and planning of road maintenance, which is fundamental to prevent and minimize the risks to which light and heavy vehicles may be exposed during transit, and ensure the maximum safety for passengers. Nowadays, for testing of pavement of new road infrastructures, direct measurements such as drill cores are performed. Usually drillings reach a depth of about one meter from the road surface and its lateral spacing is variable, basing on the importance of the road and its constructive...
Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in te... more Sinkholes linked to cover evaporite karst in urban environments still represent a challenge in terms of their clear identification and mapping considering the rehash and man-made structures. In the present research, we have proposed and tested a methodology to identify the subsiding features through an integrated and non-invasive multi-scale approach combining seismic reflection, PS-InSAR (PSI), leveling and full 3D Ground Penetrating Radar (GPR), and thus overpassing the limits of each method. The analysis was conducted in a small village in the Alta Val Tagliamento Valley (Friuli Venezia Giulia region, NE Italy). Here, sinkholes have been reported for a long time as well as the hazards linked to their presence. Within past years, several houses have been demolished and at present many of them are damaged. The PSI investigation allowed the identification of an area with higher vertical velocities; seismic reflection imagined the covered karst bedrock, identifying three depocenters;...
The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor ... more The Barents Sea Ice Sheet was a marine-based ice sheet, i.e., it rested on the Barents Sea floor during the Last Glacial Maximum (21 ky BP). The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet and is regarded as an analogue for contemporary ice streams in West Antarctica. Here, the retreat of the Bjørnøyrenna Ice Stream is simulated by means of two numerical ice sheet models and results assessed against geological data. We investigate the sensitivity of the ice stream to changes in ocean temperature and the impact of grounding-line physics on ice stream retreat. Our results suggest that the role played by sub-shelf melting depends on how the grounding-line physics is represented in the models. When an analytic constraint on the ice flux across the grounding line is applied, the retreat of Bjørnøyrenna Ice Stream is primarily driven by internal ice dynamics rather than by oceanic forcing. This suggests that implementations of grounding-line physics need to be carefully assessed when evaluating and predicting the response of contemporary marine-based ice sheets and individual ice streams to ongoing and future ocean warming. The Eurasian Ice Sheet Complex during the Last Glacial Maximum (LGM, 21 ky BP) comprised three large ice sheets: the British-Irish Ice Sheet, the Fennoscandian Ice Sheet and the Barents Sea Ice Sheet 1. In particular, the Barents Sea Ice Sheet was largely marine based, as its largest portion rested hundreds of meters below sea level on the Barents Sea floor. The Bjørnøyrenna Ice Stream was the largest ice stream draining the Barents Sea Ice Sheet 2. At the LGM the ice stream extended up to the continental shelf edge in the western Barents Sea 3 (Fig. 1). Sediment cores from the outer shelf in the southwestern Barents Sea suggest that the Bjørnøyrenna Ice Stream started to retreat from the outer shelf to the inner part of Bjørnøyrenna between 17.1-16.1 ky BP 4 , (Fig. 1). Geological data show that the ice Stream had northern and eastern tributaries extending into the central Barents Sea, sourced from Storbanken/Storbankrenna and Sentralbankrenna/Sentralbanken respectively. Dates from glacimarine sediments suggest that the deglaciation of Sentraldjupet to the east of Bjørnøyrenna started between 15.2-14.8 ky BP 5 , and that ice-free conditions prevailed after 11.3-10.9 ky BP 6 (Fig. 1). Due to similar morphological and glaciological features, the Bjørnøyrenna Ice Stream is acknowledged as an analogue for several present-day ice streams in the West Antarctic Ice Sheet (WAIS) 7. Therefore, it is interesting to identify the dynamic processes driving the retreat of the Bjørnøyrenna Ice Stream over the western Barents Sea continental shelf during the last deglaciation. Here, we focus on the role exerted by the sub-shelf melting and by grounding-line dynamics as triggers of the ice stream retreat. Several recent studies show that ice shelves and
Sinkholes are a well-known geologic hazard but their past occurrence, useful for subsidence risk ... more Sinkholes are a well-known geologic hazard but their past occurrence, useful for subsidence risk prediction, is difficult to define, especially for ancient historic times. Consequently, our knowledge about Holocene carbonate landscapes is often limited. A multidisciplinary study of Trieste Karst (Italy), close to early Roman military fortifications, led to the identification of possible ancient road tracks, cut by at least one sinkhole. Electrical Resistivity Tomography through the sinkhole has suggested the presence of a cave below its bottom, possibly responsible of the sinkhole formation, while Ground Penetrating Radar has detected no tectonic disturbances underneath the tracks. Additionally, archaeological surveys led to the discovery of over 200 Roman shoe hobnails within or close to the investigated route. According to these data, the tracks are interpreted as the remains of a main Roman road, whose itinerary has been reconstructed for more than 4 km together with other elemen...
The damage and the eventual breach of river embankments may be due to internal erosion and instab... more The damage and the eventual breach of river embankments may be due to internal erosion and instability processes in the waterside and landside slopes. Beside the progressive degradation of soil properties, different types of macro-pores inside the levee body can influence its short-and long-term performance. Among macropores, burrows are a widespread form of biologic erosion of earthen structures potentially producing damage or even their collapse. In fact, animal burrows are erosion tunnels, which can lead to piping phenomena. Thus, the emergent risk connected to burrowing animals in earthen levees has to be tackled, given also the environmental changes driven by human activity and climate. Remote sensing and geophysical surveys can complement data from in situ investigation campaigns in the definition of the real-embankment model, as well as in the imaging of local defects which may influence its local and/or global stability. Several techniques were integrated in the study area of the Panaro River, where an active animal burrow was detected in spring 2015. Two campaigns were carried out: Survey-1, in June 2015, just after the relocation of the animals, and Survey-2 in December 2015, after the filling of the burrow with a cement-bentonite slurry. Here, we highlight the peculiarity of each method and the choice of an integrated multi-technique approach. The results allowed the known burrow, as well as two other tunnels, to be imaged in 3D, providing specific guidelines for the best integrated strategy to detect and characterize these macro-pores in a fluvial levee. The proposed approach can advance our knowledge of embankments in space and time, so that effective remedial actions in flood risk and wildlife management can be identified.
The southeastern European Alps represent the spot where mean annual precipitation is at its highe... more The southeastern European Alps represent the spot where mean annual precipitation is at its highest in the entire Alpine chain. Accordingly, the glacial evolution here might have a different spatial and chronological pattern if compared with other alpine areas. This paper discusses geomorphological evidence of three glacial stages from the Krnica Valley in the Julian Alps of Slovenia, and is the first step towards a comprehensive palaeoglaciological studies in this alpine sector. Very well-preserved glacial landforms in the Upper Krnica Valley allowed the reconstruction of glacier surface topographies and corresponding equilibrium line altitudes (ELAs) by means of field-based geomorphological and sedimentological data and by using geospatial analysis. The uppermost frontal moraines belong to the Little Ice Age (LIA) and the corresponding ELA is estimated at 1973 m a.s.l. Other two stages with the ELA depressed by 50 m and 161 m compared to the LIA ELA, suggest early Holocene and Younger Dryas ages of the palaeoglaciers, respectively. This assumption ensues from absolute age datings and related ELA depressions observed elsewhere in the European Alps. The presence of buried ice under the debris in the Krnica cirque, imaged through geophysical investigations, point to peculiar microclimatic conditions able to preserve relict glacier ice. This is favoured by the recursive presence of snow on the ground caused by the extreme summer shading and the significant winter snow-recharge triggered by snowblow and avalanche feeding. The possible evolution of such relict ice under the ongoing climate warming is also discussed.
The primary objective of this study is to evaluate the applicability and the effectiveness of gro... more The primary objective of this study is to evaluate the applicability and the effectiveness of ground-penetrating radar (GPR) to identify a thin burnt soil layer, buried more than 2 m below the topographic surface at the Liangzhu Site, in Southeastern China. The site was chosen for its relatively challenging conditions of GPR techniques due to electrical conductivity and to the presence of peach tree roots that produced scattering. We completed the data acquisition by using 100 and 200 MHz antennas in TE and TM broadside and cross-polarized configurations. In the data processing and interpretation phase, we used GPR attribute analysis, including instantaneous phase and geometrical attributes. Validation analysis ground-truthing performed after the geophysical surveys, validated the GPR imaging, confirmed the electrical conductivity and relative dielectric permittivity (RDP) measurements performed at different depths, and allowed a reliable quantitative correlation between GPR results and subsurface physical properties. The research demonstrates that multiple antenna configurations in GPR data acquisition combined with attribute analysis can enhance the ability to characterize prehistoric archaeological remains even in complex subsurface conditions.
We evaluate the applicability and the effectiveness of texture attribute analysis of 2-D and 3-D ... more We evaluate the applicability and the effectiveness of texture attribute analysis of 2-D and 3-D GPR datasets obtained in different archaeological environments. Textural attributes are successfully used in seismic stratigraphic studies for hydrocarbon exploration to improve the interpretation of complex subsurface structures. We use a gray-level co-occurrence matrix (GLCM) algorithm to compute second-order statistical measures of textural characteristics, such as contrast, energy, entropy, and homogeneity. Textural attributes provide specific information about the data, and can highlight characteristics as uniformity or complexity, which complement the interpretation of amplitude data and integrate the features extracted from conventional attributes. The results from three archaeological case studies demonstrate that the proposed texture analysis can enhance understanding of GPR data by providing clearer images of distribution, volume, and shape of potential archaeological targets and related stratigraphic units, particularly in combination with the conventional GPR attributes. Such strategy improves the interpretability of GPR data, and can be very helpful for archaeological excavation planning and, more generally, for buried cultural heritage assessment.
It is well known that small glaciers of mid latitudes and especially those located at low altitud... more It is well known that small glaciers of mid latitudes and especially those located at low altitude respond suddenly to climate changes both on local and global scale. For this reason their monitoring as well as evaluation of their extension and volume is essential. We present a ground penetrating radar (GPR) dataset acquired on September 23 and 24, 2013 on the Triglav glacier to identify layers with different characteristics (snow, firn, ice, debris) within the glacier and to define the extension and volume of the actual ice. Computing integrated and interpolated 3D using the whole GPR dataset, we estimate that at the moment of data acquisition the ice area was 3800 m 2 and the ice volume 7400 m 3. Its average thickness was 1.95 m while its maximum thickness was slightly more than 5 m. Here we compare the results with a previous GPR survey acquired in 2000. A critical review of the historical data to find the general trend and to forecast a possible evolution is also presented. Between 2000 and 2013, we observed relevant changes in the internal distribution of the different units (snow, firn, ice) and the ice volume reduced from about 35,000 m 3 to about 7400 m 3. Such result can be achieved only using multiple GPR surveys, which allow not only to assess the volume occupied by a glacial body, but also to image its internal structure and the actual ice volume. In fact, by applying one of the widely used empirical volume-area relations to infer the geometrical parameters of the glacier, a relevant underestimation of ice-loss would be achieved.
We evaluate the applicability and the effectiveness of GPR attribute analysis for high-resolution... more We evaluate the applicability and the effectiveness of GPR attribute analysis for high-resolution glacier imaging and characterization, testing this approach on 4-D GPR multifrequency data collected in a small glacier in the Eastern Alps, by repeating the acquisition along the same profiles in four different periods of the year 2013. The main objectives are to image and characterize the glacier's inner structure and to quantitatively monitor the seasonal thawing of near-surface frozen materials (snow/firn). A multiattribute approach is used to characterize the subsurface through different attribute categories, including instantaneous and textural attributes considering not only amplitude-, phase-and frequency-related attributes, but also other more complex and integrated parameters. We combine information from more than one attribute into a single image with composite displays, using overlays or mixed displays. The results demonstrate that the developed GPR attribute analysis can provide significant improvements in the discrimination of GPR signals, and obtain enhanced and more constrained data interpretations.
The Montasio Occidentale glacier is a 0.07 km2 wide, avalanche-fed glacier located at very low-al... more The Montasio Occidentale glacier is a 0.07 km2 wide, avalanche-fed glacier located at very low-altitude (1860- 2050 m a.s.l.) in the Eastern Italian Alps. The glacier is still active and shows a detectable mass transfer from the accumulation area to the lower ablation area, which is covered by a thick debris mantle. Geometric changes and mass balance have been monitored starting in 2010, combining glaciological methods and high-resolution geodetic surveying with a terrestrial laser scanner (TLS). The TLS technique has proved to be very effective in determining the volume change of this glacier, but presents several limitations as high costs, high level of specialized training and low portability. On the other hand, the recent improvements in close-range photogrammetric techniques like the Structure from Motion (SfM), combined with dense image matching algorithms as Multi View Stereo (MVS), make them competitive for high quality 3D models production. The purpose of this work was to a...
The activation of Late Quaternary faults in the Central Apennines (Italy) could generate earthqua... more The activation of Late Quaternary faults in the Central Apennines (Italy) could generate earthquakes with magnitude of about 6.5, and the Monte Vettore fault system probably belongs to the same category of seismogenetic faults. Such structure has been defined 'silent', because of its geological and geomorphological evidences of past activation, but the absence of historical records in the seismic catalogues to be associated with its activation. The 'Piano di Castelluccio' intramountain basin, resulting from the Quaternary activity of normal faults, is characterized by a secondary fault strand highlighted by a NW-SE fault scarp: it has been already studied through palaeoseismological trenches, which highlighted evidences of Quaternary shallow faulting due to strong earthquakes, and through a 2-D ground penetrating radar (GPR) survey, showing the first geophysical signature of faulting for this site. Within the same place, a 3-D GPR volume over a 20 × 20 m area has been collected. The collection of radar echoes in three dimensions allows to map both the vertical and lateral continuity of shallow geometries of the fault zone (Fz), imaging features with high resolution, ranging from few metres to centimetres and therefore imaging also local variations at the microscale. Several geophysical markers of faulting, already highlighted on this site, have been taken as reference to plan the 3-D survey. In this paper, we provide the first 3-D subsurface imaging of an active shallow fault belonging to the Umbria-Marche Apennine highlighting the subsurface fault geometry and the stratigraphic sequence up to a depth of about 5 m. From our data, geophysical faulting signatures are clearly visible in three dimensions: diffraction hyperbolas, truncations of layers, local attenuated zones and varying dip of the layers have been detected within the Fz. The interpretation of the 3-D data set provided qualitative and quantitative geological information in addition to the fault location, like its geometry, boundaries and an estimation of the fault throw.
Proceedings of the National Academy of Sciences of the United States of America, Jan 16, 2015
An interdisciplinary study of the archaeological landscape of the Trieste area (northeastern Ital... more An interdisciplinary study of the archaeological landscape of the Trieste area (northeastern Italy), mainly based on airborne light detection and ranging (LiDAR), ground penetrating radar (GPR), and archaeological surveys, has led to the discovery of an early Roman fortification system, composed of a big central camp (San Rocco) flanked by two minor forts. The most ancient archaeological findings, including a Greco-Italic amphora rim produced in Latium or Campania, provide a relative chronology for the first installation of the structures between the end of the third century B.C. and the first decades of the second century B.C. whereas other materials, such as Lamboglia 2 amphorae and a military footwear hobnail (type D of Alesia), indicate that they maintained a strategic role at least up to the mid first century B.C. According to archaeological data and literary sources, the sites were probably established in connection with the Roman conquest of the Istria peninsula in 178-177 B....
SEG Technical Program Expanded Abstracts 2003, 2003
Multi-channel Analysis of Surface Waves (MASW) is a suitable technique for vertical shear-wave ve... more Multi-channel Analysis of Surface Waves (MASW) is a suitable technique for vertical shear-wave velocity profile determination whose efficiency and effectiveness depends on data acquisition parameters and processing procedures. In the present paper we compare the performances of three different methods to determine Rayleigh waves dispersion curves. Such curves are successively exploited for the inversion process, which eventually provides subsurface information of use in geological or geotechnical applications. We investigate the role of some processing procedures, with a special emphasis on the number of traces able to optimise the ratio between information content and acquisition and processing costs. We show that phase shift method is able to produce the best results in terms of accuracy and computation efficiency for the unconsolidated sediments considered in our work. Phase shift shows extremely stable results also when a reduced number of traces is considered and other methods fail due to spatial aliasing or severe noise content that prevents from unambiguous interpretation.
A 3D multi-fold GPR investigation was canied Out in the archaeological park of Aquileia in the fr... more A 3D multi-fold GPR investigation was canied Out in the archaeological park of Aquileia in the framework of a survey proposed by the local supenntendency of cultural heritage. Primary objective of the work was the identification of targets of potential archaeological interest in a polygon of approximately 2800 sqm in area, which borders the town cemetery to the north. The comparison of single-fold and multi-fold test profiles encouraged the design of a complete multi-fold grid. The 3-D option was chosen to correlate and map targets of limited dimensions. Targets of possible archaeological interest were identified at estimated depths not exceeding 200 cm in the part of the dataset processed to date. The comparison of single-fold and multi-fold 2-D and 3-D results shows an approximate 600% SNR enhancement for most of the observed targets with a net peak for a flat reflector which represents the major shallow discontinuity in the electric prop ei-ties of the soil and it is possibly associated with the base of the chaotic layer of recent deposition.. A large number of the interpreted targets was identified by means of the integrated interpretation of stack and prestack records, velocity analysis panels and 3-D data volumes.
We exploit a combination of transmission and reflection Ground Penetrating Radar (GPR) techniques... more We exploit a combination of transmission and reflection Ground Penetrating Radar (GPR) techniques to characterize limestone at different scales (from sub-metric/metric to decametric). The integrated method is based on Multi-Fold (MF) GPR techniques to obtain radar response at different offsets (source-receiver separation) corresponding to different incidence angles. MF GPR measurements are combined with transmission tomography where possible (isolated blocks). The MF datasets allow imaging of rock conditions, characterization of rock, fractures and filling materials. Imaging of joints, fractures, voids and heterogeneous volumes is performed by means of pre-stack and post-stack time and depth imaging methods. In this work experiments are carried out from the surface or on isolated blocks using a pulse GPR system equipped with 250, 500 and 800 MHz central frequencies antennas. The results show that the integrated multi-fold/tomographic method allows enhanced characterization of limestone, compared with conventional sonic methods and proves to be highly sensitive to subtle variations in the lithological and physical properties of the rock mass.
We use an integration of Single Fold (SF), Multi fold (MF), i.e. multi offset, Multi Azimuth (MA)... more We use an integration of Single Fold (SF), Multi fold (MF), i.e. multi offset, Multi Azimuth (MA) and Multi Component (MC) or Polarimetric Ground Penetrating Radar (GPR) configurations to identify, characterize and classify targets of environmental interest. The results obtained in real and controlled conditions are validated by numerical simulations and excavation and show that MF/MA/MC GPR methods are fit for target classification in complex subsurface conditions.
Surface wave dispersion has been shown to be a valuable tool for seismic investigation of subsurf... more Surface wave dispersion has been shown to be a valuable tool for seismic investigation of subsurface structures (Park et. al., 1999; Xia et al., 1999; Dal Moro et al., 2004). Dedicated inversion procedures are highly recommended, due to the complexity of the problem, but have been generally scarcely considered. The multi-modal and highly non-linear nature of surface wave dispersion curve inversion represents a prohibitive problem for common linear inversion procedures based on the Jacobian matrix because of failures due to local minima. Fig. 1 highlights such aspect through the data regarding a 6-layer synthetic model. Various V S and thickness values were adopted for the second and third layers while the values for the other layers were set to their proper values and the rms values (objective function, ObjFN) between the actual and calculated dispersion curves plotted versus the V S and thickness ratios.
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Papers by Emanuele Forte