GPR Data Analysis Research Articles

Deep learning–based inverse analysis of GPR data for landslide hazards

In mountainous landscapes, the diverse geotechnical conditions amplify landslide susceptibility. Factors such as precipitation and seismic activity can trigger landslides, while inherent hazards such as voids, fissures, and compaction deficits jeopardize long-term slope stability. Detecting and forecasting these susceptibilities accurately is crucial. In this paper, the time-domain finite-difference approach and the gprMax software are used to conduct forward modeling of landslide susceptibility. An electrical model of subsurface aqueous structures is created, including water-filled and air-filled cavities, fracture zones, and fault lines. The distinctive radar signal responses within these environments are examined, and a dataset of B-scan images associated with their electrical models is constructed. By employing deep learning algorithms and the robust nonlinear mapping ability of convolutional neural networks in the Pix2Pix generative adversarial network, we accelerate the intelligent inversion of the geological radar data on landslide susceptibility. This innovative approach effectively reconstructs hazard models, offering a reliable basis for interpretation of radar signals.

Characterization of peat deposit using ground penetrating radar: Survey experiments and data interpretation

The paper deals with the possibilities of different wave frequency antennae applications for estimation of the depth of peat deposits and detection of peat layers with different physical characteristics. We employed a GPR system “OKO-2” (“Logical systems”, Russia) with 250 MHz, 700 MHz, and 1700 MHz shielded antennae. The surveys were conducted in 2017–2019 within the pristine and drained raised bogs and swamp forest in the south taiga subzone of Western Siberia to assess the spatial differentiation of the peat deposit and the modern peat accumulation rate within drained bogs. The peculiarities of field surveying, GPR data processing and interpretation are shown. Based on GPR data analysis the influence zone of Bakchar bog and modern peat accumulation within drained bogs were assessed. We noted that the Bakchar bog has a vast zone of influence reaching 700 m from the bog border where peat accumulation is observed. The modern peat accumulation is observed within Bakchar the bog. Drained sites of Ust-Bakchar bog are characterised by the absent peat accumulation or degradation of the peat deposits.

High-Resolution Coherency Functionals for Improving the Velocity Analysis of Ground-Penetrating Radar Data

We aim at verifying whether the use of high-resolution coherency functionals could improve the signal-to-noise ratio (S/N) of Ground-Penetrating Radar data by introducing a variable and precisely picked velocity field in the migration process. After carrying out tests on synthetic data to schematically simulate the problem, assessing the types of functionals most suitable for GPR data analysis, we estimated a varying velocity field relative to a real dataset. This dataset was acquired in an archaeological area where an excavation after a GPR survey made it possible to define the position, type, and composition of the detected targets. Two functionals, the Complex Matched Coherency Measure and the Complex Matched Analysis, turned out to be effective in computing coherency maps characterized by high-resolution and strong noise rejection, where velocity picking can be done with high precision. By using the 2D velocity field thus obtained, migration algorithms performed better than in the case of constant or 1D velocity field, with satisfactory collapsing of the diffracted events and moving of the reflected energy in the correct position. The varying velocity field was estimated on different lines and used to migrate all the GPR profiles composing the survey covering the entire archaeological area. The time slices built with the migrated profiles resulted in a higher S/N than those obtained from non-migrated or migrated at constant velocity GPR profiles. The improvements are inherent to the resolution, continuity, and energy content of linear reflective areas. On the basis of our experience, we can state that the use of high-resolution coherency functionals leads to migrated GPR profiles with a high-grade of hyperbolas focusing. These profiles favor better imaging of the targets of interest, thereby allowing for a more reliable interpretation.

Geocryological Analysis of Rocks to Predict Adverse Freeze-and-Thaw Effects

The geophysical investigations are carried out at the Kangalass open pit coal mine using the round penetrating radar and electrical tomography. The main frost effects in rock mass and in water retaining dam are described. The investigation procedure is developed, and the wave fields are characterized. The GPR surveys aimed to reveal water invasion zones in a rock block to be blasted and to trace dynamics of a seasonal thawing layer are presented. The integrated analysis of GPR and electrotomography data is performed to determine adverse freeze-and-thaw processes at the dam bottom. Applicability of GPR in prediction of unfavorable freeze-and-thaw activities is demonstrated.

3-D structure of the discharging zone of the Daginsky hydrothermal system (Sakhalin Island) according to the ground penetrating radar method and well logs

The paper presents the results of a comprehensive analysis of GPR data and geophysical well survey data (gamma-ray logging and self-polarization potentials) to study the 3-D spatial structure of the Daginsky hydrothermal system discharging zone (Sakhalin Island) and its hydrogeological situation. According to the GPR method, the paleo-valleys were identified, the morphology of which indicates the presence of runoff hollows, the accumulation of sandy-aleurite-clay sediments covered with peat formations. It can be concluded that the caprock in this area consists of a pack of water layers and permeable zones. Based on the data of geophysical studies in wells, three zones can be distinguished, each of which is characterized by the corresponding values of gamma activity and changes in the potentials of its own polarization. All this helps in identifying permeable thermally conductive zones. The data obtained are of practical importance.

Combined GPR data analysis technique for diagnostics of structures with thin near-surface layers

Combined GPR data analysis technique for diagnostics of structures with thin near-surface layers

Caracterização geológica, geomorfológica e evolutiva holocênica do litoral sul de Jaguaruna, SC, Brasil

Compreender os processos evolutivos que ocorreram para a conformação atual do ambiente costeiro é de suma importância para estudos relacionados ao planejamento e gestão do litoral. O presente trabalho tem como objetivo caracterizar a barreira costeira holocênica do setor sul de Jaguaruna, Santa Catarina, do ponto de vista geológico, geomorfológico e evolutivo, através de dados de superfície e de subsuperfície, a fim de subsidiar a gestão costeira da região. O estudo foi realizado com base na interpretação de fotografias aéreas e na análise de dados geofísicos obtidos com um GPR. Em superfície foram identificados quatro depósitos sedimentares compondo a barreira costeira: Depósito Lagunar Praial, Depósito Paludial, Depósito Eólico e Depósito Marinho Praial. Do ponto de vista geomorfológico, esses depósitos se apresentam na forma de planície de cordões litorâneos, banhados, dunas e praia, respectivamente. Além destes, cristas de precipitação e paleocanais se destacam na morfologia da barreira. Quanto às informações de subsuperfície, a principal observação está relacionada à influência do Rio Urussanga sobre o ambiente marinho raso e praial durante a evolução da barreira. A presença de paleocanais em subsuperfície, juntamente com outras informações identificadas em superfície, permitiram caracterizar o comportamento evolutivo da barreira como regressiva. As seções de GPR possibilitaram identificar os paleocanais devido à presença de uma superfície erosiva em forma côncava, com alta amplitude e continuidade lateral. Acima dessa superfície ocorre o preenchimento dos paleocanais em fases distintas. Estas informa- ções de caráter geológico e geomorfológico têm implicações importantes para o planejamento e gestão territorial.

Texture Attribute Analysis of GPR Data for Archaeological Prospection

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.

Understanding depth-amplitude effects in assessment of GPR data from concrete bridge decks

The variation of concrete cover thickness on bridge decks has been observed to significantly affect the rebar reflection amplitude of the ground penetrating radar signal. Several depth correction approaches have been previously proposed in which it is assumed that, for any bridge, at least a portion of the deck area is sound concrete. The 90th percentile linear regression is a commonly used procedure to extract the depth-amplitude relationship of the assumed sound concrete. It is recommended herein that normalizing the depth-dependent amplitudes be divided into two components. The first component takes into account the geometric loss due to inverse-square effect and the dielectric loss caused by the dissipation of electromagnetic energy in sound concrete. The second component is the conductive loss as a result of increased free charges associated with concrete deterioration. Whereas the conventional depth correction techniques do not clearly differentiate the two components and tend to incorporate both in the regression line, they are separately addressed in this research. Specifically, while the first component was accounted for based on a library of GPR signals collected from sound areas of twenty four bare concrete bridge decks, the conductive loss caused by an increased conductivity is linearly normalized by the two-way travel time. The implementation of the proposed method in two case studies showed that, while the method significantly improves the accuracy of GPR data analysis, the conventional methods may lead to a loss of information regarding the background attenuation that would indicate the overall deterioration of bridge decks.

The Use of Three-dimensional Analysis of GPR Data in Evaluation of Operational Safety of Airfield Pavements

Diagnosis of airfield pavements is an important component of airport managing. Proper diagnosis makes possible to take optimal decisions in terms of ongoing maintenance and repairs, which in the case of airfields is of particular importance, among others, in the context of seasonal changes in the intensity of air traffic. The completeness and accuracy of gathered data is important in the diagnostic activities, what means that the entire airfield road network should be measured and identification of all relevant pavement construction parameters at regular intervals should be done. These capabilities give the Ground Penetrating Radar technique (GPR), which enables the evaluation of the pavement structure in different ways and outlining different aspects of construction.GPR application as a tool supporting the process of state assessment gives a wider and better understanding of the potential damage of pavement. Properly prepared methodology of measurement, configuration and selection of the measurement system creates the possibility of observation of the investigated object, not only in a single plane of a typical radar profiling, but also in the three-dimensional image. Spatial representation obtained on the basis of synchronized profiling allows precise localization of interlayer boundaries in longitudinal and transverse directions. An important advantage of three-dimensional analysis is the ability of imaging data by the use of horizontal cuts (slices). This makes it possible to identify plane direction and depth of the cracks and crevices of concrete slabs covered with layers of asphalt or concrete. An additional element of the GPR data analysis can be quantitative assessment of dowels in concrete slabs, reinforcement of prefabricated elements supporting pavement structure, as well as location of pipes, cables, tie bars and other.The paper presents the series of examples illustrating the use of GPR technique as supporting in the process airfield pavement assessment.

GPR Data Analysis of Weak Signals Using Modified S-Transform

GPR often encounters difficulty in visualizing the buried target when signals are weak and enveloped by noise, despite using the best of existing GPR data analysis tools. In this study, new method has been proposed based on modified S-transform to analyze weak signals of GPR data. The time–frequency analysis has been implemented to capture the change in electromagnetic waves reflected at the boundary of dielectric contrast. A series of experimental tests were conducted at different site conditions and with different materials using GSSI SIR 3000 GPR system with 400 MHz antenna. An improved 2-D vertical subsurface profile has been developed using time–frequency information to locate the target spatially as well as temporally. The new method has provided better results to improve the target visualization in case of noisy signals. However, it did not add any significant where conventional processing could do reasonable. The proposed method is convenient to use and capable of processing large number of scans effectively.

Stratygrafia radarowa – metoda analizy danych georadarowych 3D w badaniu środowisk sedymentacyjnych na przykładzie osadów rzecznych

Stratygrafia radarowa – metoda analizy danych georadarowych 3D w badaniu środowisk sedymentacyjnych na przykładzie osadów rzecznych

3-D GPR data analysis for high-resolution imaging of shallow subsurface faults: the Mt Vettore case study (Central Apennines, Italy)

3-D GPR data analysis for high-resolution imaging of shallow subsurface faults: the Mt Vettore case study (Central Apennines, Italy)

Integrated analysis of waveguide dispersed GPR pulses using deterministic and Bayesian inversion methods

ABSTRACTGround‐penetrating radar (GPR) data affected by waveguide dispersion are not straightforward to analyse. Therefore, waveguide dispersed common midpoint measurements are typically interpreted using so‐called dispersion curves, which describe the phase velocity as a function of frequency. These dispersion curves are typically evaluated with deterministic optimization algorithms that derive the dielectric properties of the subsurface as well as the location and depth of the respective layers. However, these methods do not provide estimates of the uncertainty of the inferred subsurface properties. Here, we applied a formal Bayesian inversion methodology using the recently developed DiffeRential Evolution Adaptive Metropolis algorithm. This Markov Chain Monte Carlo simulation method rapidly estimates the (non‐linear) parameter uncertainty and helps to treat the measurement error explicitly. We found that the frequency range used in the inversion has an important influence on the posterior parameter estimates, essentially because parameter sensitivity varies with measurement frequency. Moreover, we established that the measurement error associated with the dispersion curve is frequency dependent and that the estimated model parameters become severely biased if this frequency‐dependent nature of the measurement error is not properly accounted for. We estimated these frequency‐dependent measurement errors together with the model parameters using the algorithm. The posterior distribution of the model parameters derived in this way compared well with inversion results for a reduced frequency bandwidth which is an alternative, yet subjective method to reduce the bias introduced by this frequency‐dependent measurement error. Altogether, our inversion procedure provides an integrated and objective methodology for the analysis of dispersive GPR data and appropriately treats the measurement error and parameter uncertainty.

High-resolution GPR data analysis using extended tree-based pursuit

Abstract Decomposition of geophysical signals (e.g., seismic and ground-penetrating radar data) into the time–frequency domain can provide valuable information for advanced interpretation (e.g., tuning effects) and processing (e.g., inverse Q-filtering). The quality of these subsequent processing steps is strongly related to the resolution of the selected time–frequency representation (TFR). In this study, we introduce a high-resolution spectral decomposition approach representing an extension of the recently proposed Tree-Based Pursuit (TBP) method. TBP significantly reduces the computational cost compared to the well known Matching Pursuit (MP) technique by introducing a tree structure prior to the actual matching procedure. Following the original implementation of TBP, we additionally incorporate waveforms commonly used in geophysical data processing and present an alternative approach to take phase shifts into account. Application of the proposed method to synthetic data and comparison of the results with other typically used decomposition approaches, illustrate the ability of our approach to provide decomposition results highly localized in both time and frequency. Applying our procedure to field GPR data illustrates its applicability to real data and provides examples for potential applications such as analyzing thin-bed responses and modulating the data frequency content.

Application of 3D visualization techniques in the analysis of GPR data for archaeology

In this work, some results of a GPR survey carried out in a 10000 m2 large archaeological site, located in Lecce (Italy) near to a necropolis dating from the Messapian to the Roman imperial age, are reported. After a preliminary survey, performed on the entire area along parallel 1 m spaced profiles using a 200 MHz and a 500 MHz antenna in single-fold continuous mode, some smaller areas were selected, where the survey was repeated decreasing the profile spacing down to 0.50 m for the lower frequency antenna and to 0.25 m for the higher one. For two selected zones (D and B) the processed data were visualized in 3D space not only by the standard time slice technique, but also by two recently proposed approaches, namely by iso-amplitude surfaces of the complex trace amplitude and by 3D projection of energy and envelope stacks. The immediacy in revealing the spatial positioning of highly reflecting bodies, such as the anomaly interpreted as an old refilled cistern in zone D, makes 3D visualization techniques very attractive in archaeological applications of GPR. Their sensitivity to the signal/noise ratio is, on the other hand, highlighted by the quite poor performance in zone B, where the only reliable result provided by all the techniques was the soil/bedrock reflection, whereas none of them could effectively enhance the visibility of weak dipping reflections noted on 2D sections and probably related to fractures or bedding planes in the calcarenitic basement. The performance of the various techniques in these two different situations allowed insights into their main advantages and drawbacks to be gained.