Néstor Bonomo - Academia.edu (original) (raw)

Libros by Néstor Bonomo

EUDEBA. Buenos Aires. ISBN 978-950-23-1651-2, 2009

Papers by Néstor Bonomo

Near Surface Geoscience 2012 – 18th European Meeting of Environmental and Engineering Geophysics, 2012

We present the results of a GPR prospection carried out at the archaeological site of Batungasta,... more We present the results of a GPR prospection carried out at the archaeological site of Batungasta, located in NW- Argentina. This site was established by the Incas during the 14th century and was later occupied during the Spaniard conquest between 15th and 16th centuries. The environmental history of the zone together with results from radiocarbon analysis led us to postulate that part of the Inca architectural arrangements were seriously damaged and buried by successive flows of a nearby river, without surface visibility and that some Inca foundations were used by the Spaniards to build adobe enclosures over previous stone foundations. In order to investigate the existence of buried remains and provide further evidences of the architectural characteristics of the possible successive occupations, seven sectors were surveyed using a constant-offset GPR configuration, with 500 Mhz antennas. These sectors were covered in orthogonal directions following grids with 0.5 m x 0.5 m cells. The analysis of the data allowed recognizing electromagnetic patterns which could be associated to the presence of walls. In six of the seven sectors, enclosures formed by probable earth and rock walls were detected and mapped. Different archaeological features and structures that completed observations on surface could be detected.

En el presente trabajo se estudian las propiedades de polarizacion de haces electromagneticos lim... more En el presente trabajo se estudian las propiedades de polarizacion de haces electromagneticos limitados cuando estos interactuan con interfases lineales y homogeneas. En particular se pone especial atencion a aquellas situaciones que requieran indefectiblemente del empleo de una descripcion vectorial, como es el caso de superficies con anisotropias geometricas y [...]

Proceedings, Sep 3, 2017

We describe a 2D-Synthetic Emitter Array methodology for improving GPR reflections altered by clu... more We describe a 2D-Synthetic Emitter Array methodology for improving GPR reflections altered by clutter and noise. We show examples in which the proposed methodology is applied to simulated datasets. The results of the methodology are compared to the results of the 1D and Single Offset methodologies. Significant improvement with respect to them is obtained.

Journal of Applied Geophysics, Dec 1, 2018

Synthetic 1D-arrays of emitters are used in the area of GPR to improve primary reflections that i... more Synthetic 1D-arrays of emitters are used in the area of GPR to improve primary reflections that in single-offset profiles show low continuity and amplitude due to the interference of clutter and noise. In this methodology, at each array position along the survey line, a series of single emitter-receiver measurements is performed, keeping the position of the receiver constant and placing consecutively the emitter at the positions of the nodes of the array grid. A definite phase relation between the traces that constitute each common receiver gather is established and used to shift them in time with respect to the reference-offset trace, and the results are averaged. The phase relations are defined in order to superpose constructively the primary reflections, and reduce the random noise and clutter. The 1D synthetic procedure is equivalent to narrowing the transmitted electromagnetic wave-front along the direction of a real 1D array, which reduces the interference produced by reflectors located in formerly illuminated regions of the soil, and directing the field along an emitters-reflector-receiver path that maximizes the amplitude of the primary reflection at the position of the receiver with respect to the other reflections. In this article, a previously developed 1D-array method is extended to 2D-arrays, and the results of the 2D extension are analyzed and compared to the results of the 1D-array, Common-Midpoint and Single Offset techniques. The proposed 2D procedure considers a rectangular, homogeneous geometry for the array and a simple phase-relation between the component traces. In addition to directing the wave-front towards the target, these settings make possible to reduce the width of the wave-front along both axes of the array, which is expected to enhance the 1D results. Since the dimensionality increases in the 2D geometry, the number of traces in the summation grows significantly, which

Near Surface 2007 - 13th EAGE European Meeting of Environmental and Engineering Geophysics, 2007

We present the results of the geoelectric and electromagnetic induction methods applied to detect... more We present the results of the geoelectric and electromagnetic induction methods applied to detect and delimit an area contaminated with hydrocarbons. The joint implementation of these methods was performed in order to enhance the resolution of the prospecting, since each method presents different sensitivity and resolution according to the physical properties of the materials. On the basis of the results of this study, stabilization/solidification methods were applied to remedy the contaminated area. Additional surveys were performed immediately after remediation showing that the contaminants were effectively encapsulated.

Proceedings, 2013

ABSTRACT We performed a geophysical study in a historical site of Buenos Aires, corresponding to ... more ABSTRACT We performed a geophysical study in a historical site of Buenos Aires, corresponding to a Jesuit Mission established during the 17th and 18th centuries. It consisted of a Church, the Cloisters, a School and a Procurator Office; also several tunnels were built, connecting the Mission with different public buildings of the town. In 19th century the Faculty of Sciences was constructed over one of the site, functioning until its demolition in 1973. At present, this space is a cobbled square. With the aim of preserving and restoring the buried structures, we worked in this square, looking for tunnels and also for remains of the basement of the old building. Taking into account both the conductive features of the soil, mainly formed by clays and silt, and the urban characteristics of the environment, we performed pre-feasibility studies to determine the penetration-depth of different methods. We obtained reliable data surveying with dipole-dipole profiles with apertures of 1.5 and 3 m, provided that the electrodes were buried at least 15 cm among the cobble stones. By correlating the resulting nine ERTs with the original plans, old structures and evidences of remains of tunnels were identified.

Journal of Applied Geophysics, Nov 1, 2016

We evaluate the simultaneous application of a synthetic-emitter array (SEA) methodology and formu... more We evaluate the simultaneous application of a synthetic-emitter array (SEA) methodology and formulation derived from the analysis of the rotation transformations of the scattering matrix (RTSM) to calculate the orientation of buried pipes from GPR data acquired along a single survey line. The main objective of this study is to analyze if the SEA-RTSM combination can improve the azimuth calculation obtained from the usual singleoffset-RTSM (SO-RTSM) procedure. This possibility is based on the SEA ability of increasing the continuity and amplitude of the primary reflections with respect to the background clutter and noise, which is expected to reduce the fluctuations involved in the RTSM calculation of the azimuth, so that its accuracy and precision are improved. A SEA methodology designed to be used in conjunction with the RTSM methodology is described. A procedure that optimizes the results of the SEA methodology is explained. A statistical RTSM calculation is adopted in order to obtain the final azimuth. Different relevant parameters of the soil and the array of emitters are varied in order to evaluate the SEA-RTSM methodology and its results. Numerically simulated and experimental data are used in this evaluation. The SEA-RTSM and the SO-RTSM results are compared between them. These results are also compared with an equivalent common-midpoint-RTSM (CMP-RTSM) calculation. Improved precision and accuracy are obtained from the SEA-RTSM methodology in the great majority of the examples. The height/ width of the resulting azimuth distribution increases 102% in average when using this procedure instead of the usual SO-RTSM procedure, the average standard deviation diminishes 12%, and the average differences between the calculated and true azimuths reduce 34%. Minor improvements with respect to SO are obtained with the CMP-RTSM methodology. The proposed SEA-RTSM methodology and its results are especially relevant in civil engineering applications in which it is necessary to know the azimuth with precision and it is not possible to acquire data following 2D grids due to obstacles in the soil surface.

Journal of Applied Geophysics, Nov 1, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Near Surface Geophysics, Feb 1, 2013

We present the results of a GPR prospecting carried out at the archaeological site of Batungasta,... more We present the results of a GPR prospecting carried out at the archaeological site of Batungasta, in the NW region of Argentina. This site was established by the Incas in the 14 th century and was later occupied during the Spaniard conquest. Environmental information obtained at this arid zone led us to postulate that parts of the site buildings had been seriously damaged and buried by seasonal flood events as well as aeolian sedimentation. Therefore, we considered applying the GPR method to investigate the existence of buried remains, their architectural characteristics and to provide further evidence about the flows that possibly affected them. This method seemed suitable to attain these goals since it usually provides a good detection capacity for architectural structures and layers in dry environments, as well as good quality maps of the soil. Seven sectors of the site were surveyed using a GPR constant-offset methodology and 500 MHz antennas. The analysis of the data allowed recognizing electromagnetic patterns that could be associated to the existence of walls. In six of the seven sectors, enclosures formed by rock-earth and earth walls were detected and mapped, confirming Incaic-Spanish and Spanish structures, respectively. A sedimentary layer produced by a large flood that covered the structures was detected and mapped, providing evidence of this kind of event and its influence on the site. The maps of this layer were also useful to indirectly visualize the 3D shapes of the discovered walls, which were unclear in many sections of the data and to detect additional anthropogenic structures with very bad preservation conditions. These structures had not been previously identified from analysis of the data sections due to the confusing aspect of the reflections produced at their irregular boundaries. In the vast majority of applications performed in archaeology, GPR surveys are carried out by maintaining a constant distance between the emitting and receiving antennae (single-offset surveys, SO). A grid of equidistant parallel survey lines is commonly deployed in order to cover the entire area of study. The separation between the lines is typically about half a metre, which is sufficient to detect most kinds of architectural structures (e.g., Bonomo et al. 2012; Piro and Campana 2012). Denser grids are occasionally acquired to increase the spatial resolution in the cross-line direction, in cases in which it is important to obtain more details of the structures or to investigate smaller objects, such as detached pieces of masonry (Bonomo et al. 2010; Novo et al. 2012). Variable-offset acquisition, particularly, common-midpoint (CMP) acquisition, is sometimes performed at selected points of the investigated area to estimate a velocity for the electromagnetic waves propagating in the soil, from which the depths of the structures can be calculated. Although the CMP methodology can produce improved images of the subsoil (Yilmaz 1987), the acquisition and processing of these kind of data are much more time consuming than in the SO methodology, so that CMP surveys are normally limited to a few midpoints or survey lines (Berard and Maillol 2007; Brown et al. 2009).

Journal of Applied Geophysics, Feb 1, 2015

We describe a GPR methodology used to investigate the internal structure of three consecutive sec... more We describe a GPR methodology used to investigate the internal structure of three consecutive sections of the cylindrical pedestal of a monument that had to be disassembled for relocation. We acquired constant-offset circular profiles and non-standard variable-offset profiles at different heights along the pedestal. In the raw data sections, the reflections of interest were hidden by significant environmental noise with frequencies that overlapped those of the transmitted pulses and varied from trace to trace. We successfully eliminated the noise by iteratively fitting sinusoidal waves in different x-t windows and by subtracting the results from the traces. The resulting sections were interesting because they exhibited numerous and varied reflections. We analysed these sections using a combination of procedures previously used for cylindrical structures and other procedures adapted from protocols commonly used for plane semi-spaces. In particular, we evaluated the information provided by the variable-offset profiles and determined how it complemented the information obtained from the constant-offset profiles. In the variable-offset profiles, multiple reflections produced at the cylinder-air interface were reliably distinguished up to the fifth-order of reflection by taking advantage of their distinctive shapes. In the constant-offset profiles, this information was used to distinguish the multiples from possible signals of internal structures or their multiples and from unwanted signals produced by the GPR system, which can be confused with the multiples. We also considered obtaining the propagation velocity across the structure with a high degree of reliability by including the travel times of higher-order multiples in the calculations. Fitting of the theoretical curves, migration and polar representations allowed for a thorough interpretation of the reflectors present in the structures. Probable reinforcement bars, circular ties, natural veins of the material and reflectors located in nearby sections of the monument were identified. The continuity of the reflectors along the pedestal was determined. On this basis, an efficient disassembly and relocation plan for the monument was designed and performed.

Geoacta, Aug 12, 2016

This paper describes the methods and results of a geophysical survey carried out with GPR at the ... more This paper describes the methods and results of a geophysical survey carried out with GPR at the historical site "Manzana de las Luces", located in the city of Buenos Aires, Argentina, whose main objective was to pinpoint a

Journal of Geophysics and Engineering, Nov 14, 2011

Frequency-domain electromagnetic induction (EMI) systems, composed of two coplanar small coils se... more Frequency-domain electromagnetic induction (EMI) systems, composed of two coplanar small coils separated by a fixed distance (EMI or SLEM), enable the rapid detection of a great variety of near-surface structures. One coil generates a controlled, primary magnetic field and the other records the variations of the induced field while the instrument is moved over the studied area. The most usual acquisition configuration corresponds to horizontal coils, with the instrument axis parallel to the prospection lines. Usually, the interpretation is based on the direct visualization of the plan-views of the data measured at each frequency. In addition, to characterize the subsoil structure in-depth, 1D inversion methods are generally applied. The aim of this work is to analyse how the system orientation affects the ability of the method to detect localized, 2D conductive structures, buried at shallow depths, and the possibility of adequately characterizing these targets through 1D inversions. We performed a survey at a test site that contains two known structures of this type, buried in almost perpendicular directions. We performed parallel prospection lines in the direction of each structure, employing, aside from the usual configuration described before, other configurations that included horizontal and vertical coils, with the instrument axis parallel and perpendicular to the lines. For comparison, we also performed a geoelectric dipole-dipole line crossing one of the targets. The features of the anomalies observed in the graphs of the EMI apparent conductivity data strongly depend on the instrument orientation. In the horizontal coil configurations, a decrease of the apparent conductivity is observed just over the targets. Besides, each vertical configuration practically detects only the target aligned with the plane of the coils, as an important positive anomaly. Through numerical simulations, performed using a 2D forward modelling method, we demonstrate that these features are indeed 2D effects associated with the localized character of the studied conductive objects. Then, we applied to the data a 1D inversion method and drawing together the results generated pseudo 3D models of the subsoil. We found that the models obtained for the vertical coil configurations provide better results. They detect the targets as conductive structures and provide a rather good estimation of their depths. Finally, we compare the EMI results with the image obtained from the 2D inversion of the geoelectrical data and analyse the causes of the observed differences.

Journal of Modern Optics, Dec 1, 1995

... RICARDO A. DEPINE and NESTOR E. BONOMO Grupo de Electromagnetismo Aplicado, Departamento de F... more ... RICARDO A. DEPINE and NESTOR E. BONOMO Grupo de Electromagnetismo Aplicado, Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon I, 1428 ... 0950-0340/95 $1000 Đ 1995 Taylor &amp; Francis Ltd ...

Journal of Archaeological Science, Dec 1, 2010

We describe an archaeo-geophysical investigation performed near the Palo Blanco archaeological si... more We describe an archaeo-geophysical investigation performed near the Palo Blanco archaeological site, Catamarca, Argentina. A large area beyond the northern limit of the site was explored with the Ground-Penetrating Radar (GPR) method in order to detect new buildings. The exploration showed signals of mud-walls in a sector that was located relatively far from the previously known buildings. A detailed survey

Simple-offset GPR reflection methodology allows obtaining very precise information in archaeologi... more Simple-offset GPR reflection methodology allows obtaining very precise information in archaeological/historical sites. However, as large amounts of data are usually acquired, their processing, analysis and interpretation can be extremely time-consuming. In this work, we present three algorithms for the automatic detection of reflections at ancient walls in SO-GPR images, based on cascade classifiers and well-known image feature descriptors: Haar, HOG and LBP. These algorithms were implemented using supervised learning, and experimental data from previous works. The best performances corresponded to the descriptor Haar. With only two cascade stages, remarkably accurate results were attained despite the complex characteristics of the signals of the walls. Almost all of them were detected near their actual positions, and only a few false positive predictions were obtained, mostly without any continuity across the profiles. The main advantage of these methodologies is that once an accurate and reliable algorithm is implemented using data from an appropriate sector, it can be applied in all the zones of the site with similar characteristics, or even in other site of the same type. Thereby, a precise representation of the target structures is rapidly obtained, and the qualified interpreter only has to examine some parts of particular profiles.

$Research paper thumbnail of Aberrationless approach for diffraction of pulses at linear interfaces$

Optics Communications, Apr 1, 2001

ABSTRACT The diffraction of temporally Gaussian shaped light pulses is theoretically studied by m... more ABSTRACT The diffraction of temporally Gaussian shaped light pulses is theoretically studied by means of the aberrationless approach, a theoretical technique previously used for spatially bounded beams of unlimited time extension and which is extended here to time domain. We consider linear interfaces, that is, we assume that the spectral components of the vector field in the diffracted pulse are linearly related with the spectral components of the vector field in the incident pulse. In our analysis pulse deformations are described in terms of the following effects: time delay, focal displacement, waist modification and change in propagation velocity. Expressions for these effects, the time domain analogues of those already reported in the spatial domain, are given and compared with those obtained using the stationary phase method. The theory is used to calculate deformations of a short light pulse at a flat interface near conditions of total internal reflection.

Earth, Planets and Space, May 1, 2002

In this article we analyze the sensitivity of a geoelectrical modeling technique to image 2D shal... more In this article we analyze the sensitivity of a geoelectrical modeling technique to image 2D shallow structures. Firstly, we extend a previously developed 2D method based on Rayleigh-Fourier expansions, in order to allow arbitrary locations for the electrodes and also 3D earth models. This method is an alternative to finite element and finite difference techniques and is especially suitable to model multilayered structures, with smooth irregular boundaries. Then, for simple 2D models we build up two synthetic pseudosections, one for electrode deployments parallel to a profile perpendicular to the strike, and other for deployments perpendicular to it. We analyze the advantages in using both pseudosections to model these structures. We also compare geoelectric results with the corresponding audiomagnetotelluric transverse electric and transverse magnetic responses. Finally, we perform a geoelectrical survey to image a shallow buried structure and show the goodness of the model fit obtained considering both pseudosections. For the examples studied here, we conclude that considering both pseudosections leads to a more accurate description of the structures. When a 2D anomaly is present, its effect on the perpendicular component is more focused, both in width and depth, than in the parallel component. Hence the perpendicular component helps to constrain the localization of the inhomogeneity. In addition, we find similarities between the geoelectric parallel and perpendicular responses and the corresponding audiomagnetotelluric transverse magnetic and transverse electric results, respectively. When inverting audiomagnetotelluric data using 2D codes, better resolution in the electrical imaging is obtained when both modes are considered; then it is expected that 2D imaging of geoelectric data including both arrays should lead to an optimization of the inversion process. Even more, if results of these inversions could be used in correlation with AMT results, it is clear that this kind of joint inversion should contribute to remove uncertainties allowing an improvement in the description of the actual structures.