Ground Penetrating Radar Radargrams Research Articles

GPR target detection using a neural network classifier designed by a multi-objective genetic algorithm

Ground Penetrating Radar (GPR) is an electromagnetic sensing technology employed for localization of underground utilities, pipes, and other types of objects. The radargrams typically obtained have a high dimensionality, containing a number of signatures with hyperbolic pattern shapes, and can be processed to retrieve information about the target’s locations, depths and material type of underground soil. The classical Hough Transform approach used to reconstruct these hyperbola shapes is computationally expensive, given the large dimensionality of the radargrams. In literature, several approaches propose to first approximate the location of hyperbolas to small segments through a classification stage, before applying the Hough transform over these segments. However, the published classifiers designed for this task present a relatively complex architecture.Aiming at an improved target localization, we propose an alternative classification methodology. The goal is to classify windows of GPR radargrams into two classes (with or without target) using a neural network radial basis function (RBF), designed via a multi-objective genetic algorithm (MOGA). To capture samples’ fine details, high order statistic cumulant features (HOS) were used. Feature selection was performed by MOGA, with an optional prior reduction using a mutual information (MIFS) approach. The obtained results demonstrate improvement of the classification performance when compared with other models designed with the same data and are among the best results available in the literature, albeit the large reduction in classifier complexity.

Non-invasive estimation of root zone soil moisture from coarse root reflections in ground-penetrating radar images

Root zone soil moisture is an important component in water cycling through the soil-plant-atmosphere continuum. However, its measurement in the field remains a challenge, especially non-invasively and repeatedly. Here, we developed a new method that uses ground-penetrating radar (GPR) to quantify root zone soil moisture. Coarse roots were chosen as reflectors to collect GPR radargrams. An automatic hyperbola detection algorithm identified coarse root reflections in GPR radargrams and determined the velocity of GPR wave, which then was used to calculate the average soil water content of a soil profile (ASWC) and soil water content in a depth interval (ISWC). In total, GPR reflection data of 55 root samples from three computer simulation scenarios and two field experiments in sandy shrubland, one burying roots at known depths and the other under the undisturbed condition, were used to evaluate the proposed method. Both the simulated and the field collected data demonstrated the effectiveness of the proposed method for measuring root zone soil moisture with high accuracy. Even in the two field experiments, the root-mean-square errors of the estimated ASWC and ISWC relative to measurements from soil cores were as low as 0.003 and 0.012 m3·m−3, respectively. The proposed method offers a new way of quantifying root zone soil moisture non-invasively that allows repeated measurements. This study expands the application of GPR in root and soil study and enhances our ability to monitor plant-soil-water interactions.

Forensic Investigations of Geohazards: The Norcia 2016 Earthquake

Earthquakes represent one of the world’s most significant hazards in terms of damage to human and animal life, and property. Earthquakes also cause many other related fatalities and damage to urban structures. This paper presents the forensic investigation of failures induced by the Norcia 2016 earthquake in Italy. The detailed geophysical field investigations were carried out at selected locations in two cities: Rome and Amelia. The places of investigation were 150 km and 90 km, respectively, from the epicenter. A ground penetrating radar (GPR) survey was carried out at the sites to highlight structural failures, and included a partially damaged urban bridge, and the cracked wall of a private house. These failures have been discussed with reference to the field measurements carried out. In both cases, the GPR radargram showed clear lesions along with their geometry and location. This forensic geoscientific analysis highlights the importance of detecting structural damage immediately after a geohazard event to help plan proper interventions, efforts to prevent human losses and help law enforcement to focus their forensic investigations.

Identification of Karstic Features in Lateritic Soil by an Integrated Geophysical Approach

Lateritic soils are widely spread across the southern and central parts of India. Lateritic formations usually have soft sediments, entrapped between hard to medium soft lateritic rock, which are leached due to the ingress of water during rainy seasons creating hollow sections or cavities which span over large lengths. Laterites are highly heterogeneous and prone to cavitation due to its weathering process; a sound knowledge of the subsurface condition is required before starting any construction. This study presents the application of integrated geophysical investigation for the identification of cavities at a mega construction site in Kerala State, India. Geophysical survey methods, namely ground penetrating radar (GPR) and multichannel analysis of surface waves (MASWs) techniques, are used to identify the heterogeneities in lateritic soils and localized cavities. The survey areas identified are critical sections of a mega construction project subjected to heavy dynamic and static loads. The preliminary GPR survey is carried out across the study areas at specific interval spacing to identify probable heterogeneities. Confirmative survey or detailed GPR and MASW surveys are carried out at the locations identified in the preliminary survey at close intervals to confirm the presence of an anomaly and identify its location. The anomalies in the GPR radargram are identified by visual inspection and trace amplitude approach. Using MASW survey, a 2D shear wave velocity profile is generated to identify low shear wave velocity zones which confirm the presence of an anomaly. On comparing the data from both GPR and MASW survey techniques, the underground cavities were successfully identified at multiple locations with further crosschecking with borings. The study further provided details on subsurface lithology at survey locations.

Application of Ground Penetrating Radar Supported by Mineralogical-Geochemical Methods for Mapping Unroofed Cave Sediments

Ground penetrating radar (GPR) using a special unshielded 50 MHz Rough Terrain Antenna (RTA) in combination with a shielded 250 MHz antenna was used to study the capability of this geophysical method for detecting cave sediments. Allochthonous cave sediments found in the study area of Lanski vrh (W Slovenia) are now exposed on the karst surface in the so-called “unroofed caves” due to a general lowering of the surface (denudation of carbonate rocks) and can provide valuable evidence of the karst development. In the first phase, GPR profiles were measured at three test locations, where cave sediments are clearly evident on the surface and appear with flowstone. It turned out that cave sediments are clearly visible on GPR radargrams as areas of strong signal attenuation. Based on this finding, GPR profiling was used in several other places where direct indicators of unroofed caves or other indicators for speleogenesis are not present due to strong surface reshaping. The influence of various field conditions, especially water content, on GPR measurements was also analysed by comparing radargrams measured in various field conditions. Further mineralogical-geochemical analyses were conducted to better understand the factors that influence the attenuation in the area of cave sediments. Samples of cave sediments and soils on carbonate rocks (rendzina) were taken for X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses to compare the mineral and geochemical compositions of both sediments. Results show that cave sediments contain higher amounts of clay minerals and iron/aluminium oxides/hydroxides which, in addition to the thickness of cave sediments, can play an important role in the depth of penetration. Differences in the mineral composition also lead to water retention in cave sediments even through dry periods which additionally contribute to increased attenuation with respect to surrounding soils. The GPR method has proven to be reliable for locating areas of cave sediments at the surface and to determine their spatial extent, which is very important in delineating the geometry of unroofed cave systems. GPR thus proved to be a very valuable method in supporting geological and geomorphological mapping for a more comprehensive recognition of unroofed cave systems. These are important for understanding karstification and speleogenetic processes that influenced the formation of former underground caves and can help us reconstruct the direction of former underground water flows.

Surface and shallow subsurface structure of the Middle Kedrovaya paleoseismic rupture zone in the Baikal Mountains from geomorphological and ground-penetrating radar investigations

The 30-km-long Middle Kedrovaya (MK) paleoseismic rupture zone, on the northwestern flank of Lake Baikal, is one of most impressive late Quaternary fault scarps in the Baikal rift. The aim of this study is to reconstruct the near-surface fault geometry of the MK fault zone to clarify its past movement history and seismic potential. We applied ground penetrating radar (GPR), along with high-resolution satellite imagery and field surface observations, to analyze the structure of the upper 12–13 m of the rupture zone and to characterize the complex structural environment in three dimensions. The GPR reveals that the shallow structure of the MK zone is defined by a combination of steep and listric normal faults, which form a surface pattern of subparallel ruptures trending predominantly N30°E. Individual surface scarps range from 5 m to 2.7 km in length and are separated by gaps of a few tens of meters to several kilometers apart. The greatest width of the scarp zone is 1.9 km. The vertical displacements measured independently from surface topographic profiles and from GPR radargrams are linearly related. The height of the main footwall (head) scarp is always 0.5–2 m greater than the throw measured on the radargrams, a result of the scarp face having broadened far up the talus slope after the latest displacement event. Maximum and average vertical normal fault displacements along the main fault trace, inferred from GPR data, are 8.3 and 4.98 m respectively. Paleoearthquake magnitude M estimated from empirical regressions ranges from 6.8 to 7.6, based on equations of M vs. surface rupture length, M vs. displacement, and M vs. landslide volume. Our study of the Middle Kedrovaya paleoseismic rupture zone confirms that listric normal faulting is widespread in the shallow (<13 m) subsurface of the western margin of the North Baikal basin. However, GPR data suggest that listric faulting is confined to the unconsolidated talus deposits and probably represents the effects of downhill gravitational sliding of the talus, and perhaps of underlying shallow bedrock. This downhill (lakeward) sliding of the hanging wall is partly responsible for the large heave component of movement on the MK rupture zone and its resulting unique geomorphic expression.This paper illustrates the practicality of investigating fault surface ruptures in complex environments by integrating data gathered by geophysics (GPR in this case) and by direct geomorphological observations. Because of the loose and mobile nature of the faulted talus deposit, the current surface morphology disguises the true number of subsurface faults, the lateral extent of faulting, and the unique structure types (all visible on radargrams) that developed to accommodate coseismic surface rupture with a large heave component.

Detection of Root Orientation Using Ground-Penetrating Radar

Due to its in situ and nondestructive nature, ground-penetrating radar (GPR) has recently been applied to the field investigation of plant roots. The discrepancy between the roots and surrounding soils creates a dielectric constant contrast, forming clear hyperbolic reflections on the GPR radargram. The intensity and shape of the reflecting signals from roots are substantially affected by the root orientation as well as the relative geometry between the root in the subsurface and the GPR survey direction on the ground surface. However, no previous study has utilized the information on the intensity and shape of a root’s GPR reflection to map its orientation, which is crucial in interpreting radargrams and rebuilding 3-D root system architecture. In this paper, a mathematical formulation of hyperbolic reflection formed by a single root was first deduced based on the principles of electromagnetic wave propagation. Then, using this formulation, curve fitting was conducted on both simulated and field collected data sets by GPR. Information on the horizontal orientation and vertical inclination of a single root was acquired according to the formulation coefficient retrievals. Conditions for this method of application and factors impacting the extraction of root orientation information were analyzed. The results indicated fairly precise root orientation estimations. The proposed method has extended the application of GPR in root investigation, thus advancing the frontier of noninvasive root system architecture mapping.

Exploration of Hard Objects in Superficial Farmland Soil using GPR

Hard objects, such as metal, stone, tree stump, etc., entirely buried into, or partly buried into, or revealed on the surface of superficial farmland soil with the depth of about 40 centimeters may hurt the cutter tools of agricultural machinery. They are also bad for seeding, fertilizing and so on. A ground penetrating radar (GPR) is used for exploring and locating the hard objects in the soil. This paper proposes the processing steps of the GPR radargrams acquired in an experiment of detecting hard objects buried in a piece of practical farmland with complex conditions and the interpretation of the result. This demonstrates that GPR is a feasible method for exploring hard objects in the superficial farmland soil.

Subsurface elements prediction for the design of forest road using ground penetrating radar technique

Reliable and accurate earthwork calculation is one of the most important components in road engineering that can influence the construction cost and road alignment choice. In this research, the method of ground penetrating radar (GPR) was applied to detect the subsoil rock share in forest road construction. The GPR data acquisition was carried out using a 250 MHz GPR antenna along 22 segments on the centerline and 12 meters across to the road project. The GPR data processing was done by performing different filters, such as background removal, migration, band pass filter, and horizontal and vertical smoothing on the GPR data. To investigate the capability of the GPR method used in this road construction project, we compared the GPR radargram and road profile after construction. The results indicated that the maximum penetration depth of the GPR waves produced by a 250 MHz GPR transmitter antenna, which were between 2 and 5 meters in fine area (clayey soil with high moisture content) and rocky grounds, respectively. Moreover, the capability of GPR to map large dimension roots and water content is presented in this work. Comparison of the GPR records with direct observations of road profiles revealed that the GPR technique can yield a wide range of information that leads to a more efficient and effective earthwork operation of forest roads, although in some parts of the road profile the expected results from the target depth of rock share were not achieved.

Investigating the Foundation of the Amphiteatrum Flavium through the Passage of Commodus

In this work we present a non-invasive investigation of the Amphiteatrum Flavium, executed using the ground penetrating radar (GPR) technique, with the aim to improve the knowledge of the construction materials and techniques employed for building foundation. Therefore, the main goal of this work is to achieve quantitative and reliable information for assessing the seismic vulnerability of the structure. The GPR survey was performed through the Passage of Commodus, excavated within the foundation for a length of about 60 m. GPR data were acquired on the floor and on the lateral walls, using different antenna frequencies (80, 200, 600, 900 MHz) as they combine good resolution and depth of investigation. On the floor dataset, we detected three equally-spaced anomalies related to old utilities parallel to the passageway, whose roof is located at a depth of 1 m. In addition to this, the GPR radargrams clearly highlight horizontal layers within the foundation, related to the sequential development of works at the time of construction. GPR dataset acquired on the wall allowed us to detect the thickness of the concrete covering the foundation and to locate the extensions of the structural elements underground. Outside the foundation, the passage is built using bricks, with external walls about 1 m thick. Therefore, GPR dataset revealed that the foundation of the Colosseum is a heterogeneous multi-layer element, with the presence of cavity networks and buried elements related to the plinths of the load-bearing structures. This work confirmed that foundation was built over time by means of subdivisions into small sectors, probably both in the horizontal and vertical directions.

SPOT-GPR: A Freeware Tool for Target Detection and Localizationin GPR Data Developed within the COST Action TU1208

SPOT-GPR (release 1.0) is a new freeware tool implementing an innovative Sub-Array Processing method, for the analysis of Ground-Penetrating Radar (GPR) data with the main purposes of detecting and localizing targets. The software is implemented in Matlab, it has a graphical user interface and a short manual. This work is the outcome of a series of three Short-Term Scientific Missions (STSMs) funded by European COoperation in Science and Technology (COST) and carried out in the framework of the COST Action TU1208 “Civil Engineering Applications of Ground Penetrating Radar” (www.GPRadar.eu). The input of the software is a GPR radargram (B-scan). The radargram is partitioned in subradargrams, composed of a few traces (A-scans) each. The multi-frequency information enclosed in each trace is exploited and a set of dominant Directions of Arrival (DoA) of the electromagnetic field is calculated for each sub-radargram. The estimated angles are triangulated, obtaining a pattern of crossings that are condensed around target locations. Such pattern is filtered, in order to remove a noisy background of unwanted crossings, and is then processed by applying a statistical procedure. Finally, the targets are detected and their positions are predicted. For DoA estimation, the MUltiple SIgnal Classification (MUSIC) algorithm is employed, in combination with the matched filter technique. To the best of our knowledge, this is the first time the matched filter technique is used for the processing of GPR data. The software has been tested on GPR synthetic radargrams, calculated by using the finite-difference time-domain simulator gprMax, with very good results.

Automatic extraction of geometrical characteristics hidden in ground-penetrating radar sectional images using simultaneous perturbation artificial bee colony algorithm

Ground-penetrating radar is one of the most effective methods of detecting shallow buried objects. Ground-penetrating radar radargram is a vertical map of the radar pulse reflections that returns from subsurface objects, and in the case of cylindrical objects, it would be a hyperbola. In order to get clear and accurate information on the presence, location, and geometry of the buried objects, the radargrams need to be interpreted. Interpretation of the results is a time-consuming task and needs an expert with vast knowledge. Development of an automatic interpretation method of B-scan ground-penetrating radar images would be an effective and efficient solution to this problem. A novel automatic interpretation method of ground-penetrating radar images, based on simultaneous perturbation artificial bee colony algorithm using tournament selection strategy, simultaneous perturbation stochastic approximation method, and new search equations, is introduced in this paper. The proposed algorithm is used to extract geometrical parameters, i.e. depth, location, and radius, of buried cylindrical objects in order to assess its accuracy. Synthetic data, simulated using GprMax2D forward modelling program, and real data, surveyed in the campus of Isfahan University of Technology, are used in the assessment. The performance of the proposed method in detecting synthetic hyperbolas is compared with that of the original artificial bee colony algorithm, genetic algorithm, and modified Hough transform. The results show superiority of the proposed algorithm, in detecting synthetic hyperbolas. Furthermore, the performance of the proposed method in estimating depth and radius of pipes in real ground-penetrating radar images is compared with that of the modified Hough transform. The results indicate higher accuracy of the proposed method in estimating geometrical parameters of the buried cylindrical objects.

GROUND PENETRATING RADAR IN CIVIL ENGINEERING APPLICATION: CASE STUDY OF MULTISTOREY BUILDING FOUNDATION SITE TO MAPING SUBSURFACE FEATURES AT THE CENTER OF KARBALA GOVERNORATE, IRAQ

The reconstruction of holy shrines and religious places in Iraq was developed after 2003. At the same time, some geotechnical problems are urgently waiting to be solved. Ground Penetrating Radar (GPR) is a noninvasive technology that has many applications including subsurface geology, archeology, engineering and environmental studies. It is very effective in solving some engineering and geological problems and detecting buried objects under the ground and helping to map subsurface geological structures, subsurface soil conditions and groundwater contaminants.This paper demonstrates the utility of using GPR for mapping and locating subsurface features of multistorey building foundation site at the center Karbala district, Karbala governorate. A series of GPR profiles were acquired on a proposed multistory building site GPR survey has been carried out along fifteen profiles, ten longitudinal parallel profiles and the other profiles are transversal. In this study different antennas were chosen to conduct the survey, the antenna frequencies of 450 MHz and 750 MHz were used. The data were performed by using a commercial GPR system A MALÅ ProEx SystemTM from MALA Geoscience and we are usingRadExplorer software for processing the data. The profiles reflect a lot of subsurface features. Most of the main subsurface features anomalies due to weak zones. These zones spreading in the front and especially in the center of a building starts from under the foundation to a depth of approximately six m. The water table depth at the site was defined from GPR radargrams at a depth of (2.7 and 3.5 m). Through years of practical experience with GPR surveys, we have summed up a suitable technique to solve various engineering and geotechnical engineering problems with GPR in Iraq.

Template-matching based detection of hyperbolas in ground-penetrating radargrams for buried utilities

Ground-penetrating radar (GPR) is a mature geophysical technique that is used to map utility pipelines buried within 1.5 m of the ground surface in the urban landscape. In this work, the template-matching algorithm has been originally applied to the detection and localization of pipe signatures in two perpendicular antenna polarizations. The processing of a GPR radargram is based on four main steps. The first step consists in defining a template, usually from finite-difference time-domain simulations, made of the nearby area of the hyperbola apex associated with the mean size object to be detected in the soil, whose mean permittivity has been previously experimentally estimated. In the second step, the raw radargram is pre-processed to correct variations due to antenna coupling, then the template matching algorithm is used to detect and localize individual hyperbola signatures in an environment containing unwanted reflections, noise and overlapping signatures. The distance between the shifted template and a local zone in the radargram, based on the L1 norm, allows us to obtain a map of distances. A user-defined threshold allows us to select a reduced number of zones having a high similarity measure. In the third step, minimum or maximum discrete amplitudes belonging to a selected hyperbola curve are semi-automatically extracted in each zone. In the fourth step, the discrete hyperbola data (i, j) are fitted by a parametric hyperbola model using a non-linear least squares criterion. The algorithm was implemented and evaluated on numerical radargrams, and afterwards on experimental radargrams.

Geophysical investigation of underground water content zones using electrical resistivity tomography and ground penetrating radar: A case study in Hesarak-Karaj, Iran

This paper describes the successful application of an integrated geophysical survey to investigate the depth of underground water table and the location of probable cavity occurrences at a developing residential area to design the foundation of under constructing urban buildings located at Hesarak-Karaj, Alborz province of Iran. The integrated shallow and non-invasive geophysical survey consists of Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR). These methods could appropriately indicate the existence of the water table at a depth of approximately 12m while processed GPR radargrams localized no cavity occurrences in the studied site. A 100-MHz shielded GPR antenna has been used to conduct a high resolution shallow subsurface survey in order to delineate probable cavities of the area, and two electrical arrays of gradient and Wenner have been used as well to image resistivity variations of subsurface layers especially for prospecting water saturated zone. The acquired results which were in good accordance with the reality of the studied area at locating water table and cavity occurrences could effectively provide guidance to builders in order to tackle water flow issue and not to concern about filling cavities during constructing any building in the site.

Buried Object Discrimination in a Ground Penetrating Radar Radargram

Ground Penetrating Radar (GPR) is a non- destructive technique used for the location of objects or interfaces buried beneath the earth's surface or located within a visually opaque structure. This research work proposes techniques for buried object discrimination for the images generated by GPR by using GPR frequency-domain spectral features. The motivation for this approach comes from the fact that landmine targets and clutter objects often have different shapes and/or composition, yielding different Energy Density Spectrum (EDS) that may be exploited for their discrimination. The proposed system comprises cascade of two stages: Pre - Processing Stage, followed by Discrimination Stage. Pre - Processing eliminates the ground bounce and clutter to get an enhanced image. Enhancement is followed by Landmine or clutter Discrimination using Energy Density Spectrum. All implementations are done using MATLAB.

Buried Object Discrimination in a Ground Penetrating Radar Radargram

Buried Object Discrimination in a Ground Penetrating Radar Radargram

3D Imaging of Buried Dielectric Targets with a Tomographic Microwave Approach Applied to GPR Synthetic Data

Effective diagnostics with ground penetrating radar (GPR) is strongly dependent on the amount and quality of available data as well as on the efficiency of the adopted imaging procedure. In this frame, the aim of the present work is to investigate the capability of a typical GPR system placed at a ground interface to derive three-dimensional (3D) information on the features of buried dielectric targets (location, dimension, and shape). The scatterers can have size comparable to the resolution limits and can be placed in the shallow subsurface in the antenna near field. Referring to canonical multimonostatic configurations, the forward scattering problem is analyzed first, obtaining a variety of synthetic GPR traces and radargrams by means of a customized implementation of an electromagnetic CAD tool. By employing these numerical data, a full 3D frequency-domain microwave tomographic approach, specifically designed for the inversion problem at hand, is applied to tackle the imaging process. The method is tested here by considering various scatterers, with different shapes and dielectric contrasts. The selected tomographic results illustrate the aptitude of the proposed approach to recover the fundamental features of the targets even with critical GPR settings.

Application of ground penetrating radar for coarse root detection and quantification: a review

Because of the crucial role coarse roots (>2 mm diameter) play in plant functions and terrestrial ecosystems, detecting and quantifying the size, architecture, and biomass of coarse roots are important. Traditional excavation methods are labor intensive and destructive, with limited quantification and repeatability of measurements over time. As a nondestructive geophysical tool for delineating buried features in shallow subsurface, ground penetrating radar (GPR) has been applied for coarse root detection since 1999. This article reviews the state-of-knowledge of coarse root detection and quantification using GPR, and discusses its potentials, constraints, possible solutions, and future outlooks. Some useful suggestions are provided that can guide future studies in this field. The feasibility and accuracy of coarse root investigation by GPR have been tested in various site conditions (mostly in controlled conditions or within plantations) and for different plant species (mostly tree root systems). Thus far, single coarse root identification and coarse root system mapping have been conducted using GPR, including roots under pavements in urban environment. Coarse root diameter and biomass have been estimated from indexes extracted from root GPR radargrams. Coarse root development can be observed by repeated GPR scanning over time. Successful GPR-based coarse root investigation is site specific, and only under suitable conditions can reliable measurements be accomplished. The best quality of root detection by GPR is achieved in well-drained and electrically-resistive soils (such as sands) under dry conditions. Numerous factors such as local soil conditions, root electromagnetic properties, and GPR antenna frequency can impact the reliability and accuracy of GPR detection and quantification of coarse roots. As GPR design, data processing software, field data collection protocols, and root parameters estimation methods are continuously improved, this noninvasive technique could offer greater potential to study coarse roots.

Large-scale internal structure of the Sanbongi Fan–Towada Volcano, Japan: Putting the theory to the test, using GPR on volcaniclastic deposits

The Towada Caldera Volcano is located between the prefectures of Aomori and Akita — Northeast Honshu Island, Japan. The caldera, today filled by a lake, has produced 15,000years ago a complex eruption emplacing an ignimbrite topped by the lake outburst flood deposit, through which the present Oirase River erodes. This flood deposit has shaped the geomorphologic feature named Sanbongi Fan, on which Towada City extends. This flood event hypothesis is mainly based on sedimentological and geomorphological evidences of floods mainly from outcrops retrieved from the Sanbongi Fan area. Because of the lack of extended outcrops – typical of the Japanese environment – the present paper has therefore put the theory to the test using GPR (Ground Penetrating Radar) radargram extending along a 640m length. The GPR used for the survey was a Pulse-ekko-Pro with 50MHz antennas, and the software Reflex was used to process the data. The radargrams have displayed a sole unit, which the GPR could not penetrate. It can be interpreted as the ignimbrite. On top of this deposit a series of subhorizontal layers, with the alternation between a backset and a foreset extends between 5m and 3m depth. Above 3m, the units are regular and subhorizontal. The deposit is also characterized by the extensive presence of boulders, which are located along three bands: (1) on top of the ignimbrite; (2) in the units deposited by the outburst flood, between 3 and 5m depths; (3) and in the units close to the surface, although part of these punctual elements are most certainly anthropogenic. Compared with the outcrops, the present research confirms that the material located above the ignimbrite material have been deposited by the outburst flood, creating large-sheet patterns, which have transported boulders. These sheets display backset and foreset patterns, depending on the position of the deposit, indicating flow pulsation or surges under a ‘high-energy-flow’ condition.