Raphael Di Carlo - Academia.edu (original) (raw)

Papers by Raphael Di Carlo

Research paper thumbnail of Ferramentas da Web 2.0 como meio de difusão das geociências: o caso do blog e página Estudando Geofísica

13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013, 2013

Contents of this paper were reviewed by the Technical Committee of the 13 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 13 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Inversão gravimétrica rápida do relevo do embasamento aplicando o funcional da variação total

We present a new 2D linear inversion gravity method to estimate the discontinuous basement relief... more We present a new 2D linear inversion gravity method to estimate the discontinuous basement relief of a sedimentary basin. The method uses an interpretation model consisting of a set of 2D juxtaposed horizontal ribbons whose thicknesses are the parameters to be estimated. The density contrast between the basement and the sediments is assumed constant and known. The estimates of the thicknesses were stabilized with the Total Variation functional (TV) which permits solutions presenting local discontinuities in the basement relief. The estimates of the basement relief are produced by solving a single linear system of equations in the L1 norm. Because linear inversion methods underestimate the depth of the basement relief for sedimentary basins thicker than 500 m, we amplify the depth estimates through by modifying the matrix associated with the interpretation model. This procedure in general leads to overestimated depths which are corrected through the expression of the anomaly of a Bou...

Research paper thumbnail of Separation of PP and PS converted waves applied in mining exploration

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

This paper was prepared for presentation during the 16 th International Congress of the Brazilian... more This paper was prepared for presentation during the 16 th International Congress of the Brazilian Geophysical Society held in Rio de Janeiro, Brazil, 19-22 August 2019. Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Separation of PP‐ and PS‐wave reflected seismic data using two‐dimensional finite offset common‐reflection‐surface traveltime approximation

Geophysical Prospecting, 2020

Recently, the interest in PS‐converted waves has increased for several applications, such as sub‐... more Recently, the interest in PS‐converted waves has increased for several applications, such as sub‐basalt layer imaging, impedance estimates and amplitude‐versus‐offset analysis. In this study, we consider the problem of separation of PP‐ and PS‐waves from pre‐stacked multicomponent seismic data in two‐dimensional isotropic medium. We aim to demonstrate that the finite‐offset common‐reflection‐surface traveltime approximation is a good alternative for separating PP‐ and PS‐converted waves in common‐offset and common shot configurations by considering a two‐dimensional isotropic medium. The five parameters of the finite‐offset common‐reflection‐surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle, one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP‐ and PS‐converted waves were separated, the sections are stacked to increase the signal‐to‐noise ratio using the special curves derived from finite‐offset common‐reflection‐surface approximation. We applied this methodology to a synthetic dataset from simple‐layered to complex‐structured media. The numerical results showed that the inverted parameters of the finite offset common‐reflection‐surface and the separation function yield good results for separating PP‐ and PS‐converted waves in noisy common‐offset and common shot gathers.

Research paper thumbnail of Basement relief estimative of the Parnaíba basin´s west border through 2D gravity modelling

Proceedings of the 7 Simpósio Brasileiro de Geofísica, 2016

We present a gravity interpretation of the west border of the Parnaíba basin´s basement relief. T... more We present a gravity interpretation of the west border of the Parnaíba basin´s basement relief. The residual Bouguer anomaly produced by the basin was estimated through the information of the Moho depth and spectral analysis. We interpreted six profiles across the basin strike through 2D modelling. We obtained depths less than 2km indicating a shallow embasament compared to the main depocenter and the northeast border of the basin.

Research paper thumbnail of Regularization of P-P and P-S converted waves data through the FO-CRS traveltime approximation

Proceedings of the VIII Simpósio Brasileiro e Geofísica, 2018

We present a new method of regularization of seismic data using the finite offset common reflecti... more We present a new method of regularization of seismic data using the finite offset common reflection source (FO-CRS) traveltime approximation. This method fits curves of common reflection source to the reflection events and stacks all the amplitudes in a given aperture. The stacked amplitude, afterwards, is allocated to the time coordinate in the trace to be interpolated. We applied this method to three synthetic velocity models and the results showed the capability for regularizing converted seismic waves in stratified medium.

Research paper thumbnail of Automatic picking using coherence measurement and global optimization

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

Contents of this paper were reviewed by the Technical Committee of the 16 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Time-depth conversion using image ray and normal ray in the tau-p domain: application in synthetic data

14th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 3-6 August 2015, 2015

The time-depth seismic conversion is an important tool in seismic processing in order to obtain f... more The time-depth seismic conversion is an important tool in seismic processing in order to obtain friendly results to the interpreter. The achievement of these sections, in depth, can be accomplished by pre- and post-stacking migration and by ray tracing methods. The tracing of normal and image rays were the methodologies used in this work for such conversion. The image ray converts a post-stacked time-migrated section to depth domain using only an initial direction of propagation. The normal ray converts time-stacked sections into depth sections requiring a set of a priori initial directions, this initial set of directions is obtained by slant stack technique. The sections obtained by image ray tracing showed good accuracy in recovering the depth of reflectors. The sections obtained by normal ray tracing recovered, with great accuracy, the depth of reflectors as well as the good lateral continuity of the same.

Research paper thumbnail of Interpretação gravimétrica da Bacia do Recôncavo utilizando inversão não linear

12th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 15–18 August 2011, 2011

Research paper thumbnail of Application of PP and PS-waves separation: A case study of N4WS Carajás mineral ore, Pará, Brazil

Journal of Applied Geophysics, 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.

Research paper thumbnail of Interpretação gravimétrica do relevo do embasamento da Bacia de Taubaté através da inversão não linear com vínculo de suavidade

Proceedings of the 4 Simpósio Brasileiro de Geofísica, 2010

Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a ... more Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a opinião da SBGf ou de seus associados. É proibida a reprodução total ou parcial deste material para propósitos comerciais sem prévia autorização da SBGf.

Research paper thumbnail of Seismic velocity inversion using the FO-CRS stack in layered medium

14th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 3-6 August 2015, 2015

Research paper thumbnail of Efficient gravity inversion of discontinuous basement relief

GEOPHYSICS, 2015

We have developed a gravity inversion method to estimate a discontinuous basement relief based on... more We have developed a gravity inversion method to estimate a discontinuous basement relief based on an extended version of Bott's method that allows variable density contrasts between sediments and basement, optimizes the modulus of the solution correction at each iteration, and provides for solution stabilization. Initially, we obtain a linear approximation stabilized by the total variation functional that correctly maps the horizontal positions of the existing high-angle faults but produced poor estimates of the basin depths. Subsequent iterations update the depth estimates toward the correct values, at the same time preserving the correct fault horizontal positions. Additionally, we stabilize each solution correction by the smoothness constraint without inverting any matrix. The method was substantially more efficient than the nonlinear method, which solves a system of linear equations by the conjugate gradient method at each iteration. For 3000 parameters, it is almost four times faster than the conjugate gradient, and this ratio increased with the number of parameters.

Research paper thumbnail of Análise da modelagem 2D de dados gravimétricos da Província Alcalina de Goiás utilizando os interpoladores de mínima curvatura e IDW

Revista Sítio Novo

Obter a delineação de corpos alcalinos é de extrema importância para o mapeamento geológico, pois... more Obter a delineação de corpos alcalinos é de extrema importância para o mapeamento geológico, pois auxilia futuros estudos de prospecção. Apresentamos neste trabalho uma interpretação da anomalia gravimétrica Registro do Araguaia, pertencente à Província Alcalina de Goiás, que é caracterizada por uma série de pequenas intrusões magmáticas alcalinas de características ultramáficas a félsicas. A gravimetria é um método geofísico que consegue delinear esses corpos devido aos altos contrastes de densidade entre as intrusões e as rochas encaixantes. Apliquei a modelagem direta em um perfil de cada mapa gravimétrico interpolado, um através da mínima curvatura e outro através do inverso da distância ponderada (IDW, da sigla em inglês). A interpretação gravimétrica do perfil interpolado pela mínima curvatura mostra dois corpos sendo um aflorante, enquanto que o perfil interpolado pelo IDW mostra um corpo com profundidade em relação à superfície de 16 m. O resultado referente ao IDW é o mai...

Research paper thumbnail of Separation of PP-and PS-wave reflected seismic data using two-dimensional finite offset common-reflection-surface traveltime approximation

Geophysical Prospecting, 2020

Recently, the interest in PS-converted waves has increased for several applications, such as sub-... more Recently, the interest in PS-converted waves has increased for several applications, such as sub-basalt layer imaging, impedance estimates and amplitude-versus-offset analysis. In this study, we consider the problem of separation of PP-and PS-waves from pre-stacked multicomponent seismic data in two-dimensional isotropic medium. We aim to demonstrate that the finite-offset common-reflection-surface traveltime approximation is a good alternative for separating PP-and PS-converted waves in common-offset and common shot configurations by considering a two-dimensional isotropic medium. The five parameters of the finite-offset common-reflection-surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle , one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP-and PS-converted waves were separated, the sections are stacked to increase the signal-to-noise ratio using the special curves derived from finite-offset common-reflection-surface approximation. We applied this methodology to a synthetic dataset from simple-layered to complex-structured media. The numerical results showed that the inverted parameters of the finite offset common-reflection-surface and the separation function yield good results for separating PP-and PS-converted waves in noisy common-offset and common shot gathers.

Research paper thumbnail of Application of PP and PS-waves separation: A case study of N4WS Carajás mineral ore, Pará, Brazil.

The seismic methods are starting to be an essential tool in mining industry when the ore deposit ... more The seismic methods are starting to be an essential tool in mining industry when the ore deposit is located under a thick altered layer. The applicability of reflection and refraction seismic holds an importance in exploration surveys due to a great necessity to investigate higher depths, mainly if compressional and shear waves data are associated, then the separation of the two types of wave became necessary. We apply a new methodology of PP and PS separation based on the estimatives of the Finite Offset Common Reflection Surface (FO-CRS) attributes. The attributes estimates are performed using the Very Fast Simulated Annealing search-for inversion algorithm. Once the attributes are estimated we use them to build a separation filter, which is function of the polarization angle of the wave and the angle of the ray at the receiver. After the separation the sections were stacked in order to increase the signal-to-noise ratio. The method was applied in the so-called N4WS iron orebody, pertaining to the Mineral Province of Carajás, northern Brazil. We applied the separation in a modelled reflection dataset of the geophysical model of the target created from electrorresistivity and refraction seismic methods. The separation was performed in a common shot section and common offset sections in order to demonstrate the geometry independency of the methodology. The conclusions show that the filter could separate successfully PP and PS amplitudes from seismic sections.

Research paper thumbnail of Regularization of P-P and P-S converted waves data through the FO-CRS traveltime approximation

Anais do VII Simpósio Brasileiro de Geofísica, 2018

We present a new method of regularization of seismic data using the finite offset common... more We present a new method of regularization of seismic
data using the finite offset common reflection source (FOCRS) traveltime approximation. This method fits curves
of common reflection source to the reflection events and
stacks all the amplitudes in a given aperture. The stacked
amplitude, afterwards, is allocated to the time coordinate
in the trace to be interpolated. We applied this method to
three synthetic velocity models and the results showed
the capability for regularizing converted seismic waves in
stratified medium.

Research paper thumbnail of Interpretação Gravimétrica do Relevo do Embasamento da Bacia do Marajó

Research paper thumbnail of Interpretação gravimétrica do relevo do embasamento da Bacia de Taubaté através da inversão não linear com vínculo de suavidade

Este texto foi preparado para a apresentação no IV Simpósio Brasileiro de Geofísica, Brasília, 14... more Este texto foi preparado para a apresentação no IV Simpósio Brasileiro de Geofísica, Brasília, 14 a 17 de novembro de 2010. Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a opinião da SBGf ou de seus associados. É proibida a reprodução total ou parcial deste material para propósitos comerciais sem prévia autorização da SBGf. ____________________________________________________________________ Abstract We present a gravity interpretation of the Taubaté basin basement relief. The residual Bouguer anomaly produced by the basin was estimated through a robust polynomial fitting method. We interpreted three gravity profiles across the basin strike using the smoothness constraint. We obtained average estimated basement depths between 370 m and 940 m, indicating a very shallow basement.

Research paper thumbnail of Automatic velocity estimative through Finite Offset Common Reflection Source (FO- CRS)

The development of seismic exploration is essentially based on the understanding of subsurface ve... more The development of seismic exploration is essentially based on the understanding of subsurface velocity field, so the estimated velocities and depths in a geological environment is an important stage in processing and interpretation of seismic data. The methodology used in this work is based on the use of the inversion of consistency, which is to maximize the semblance function, calculated from pre-stack seismic data, in order to obtain information about the velocities in the subsurface. We present a study about the sensitivity of the semblance function with respect to variation of the FO-CRS parameters (finite-offfset common-reflection-surface) on reflection events from CMP gathers (common mid-point). The results obtained with synthetic data, with and without noise, show values very close to those adopted in the model, indicating the reliability of the FO-CRS approach in the inversion process.

Research paper thumbnail of Ferramentas da Web 2.0 como meio de difusão das geociências: o caso do blog e página Estudando Geofísica

13th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 26–29 August 2013, 2013

Contents of this paper were reviewed by the Technical Committee of the 13 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 13 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Inversão gravimétrica rápida do relevo do embasamento aplicando o funcional da variação total

We present a new 2D linear inversion gravity method to estimate the discontinuous basement relief... more We present a new 2D linear inversion gravity method to estimate the discontinuous basement relief of a sedimentary basin. The method uses an interpretation model consisting of a set of 2D juxtaposed horizontal ribbons whose thicknesses are the parameters to be estimated. The density contrast between the basement and the sediments is assumed constant and known. The estimates of the thicknesses were stabilized with the Total Variation functional (TV) which permits solutions presenting local discontinuities in the basement relief. The estimates of the basement relief are produced by solving a single linear system of equations in the L1 norm. Because linear inversion methods underestimate the depth of the basement relief for sedimentary basins thicker than 500 m, we amplify the depth estimates through by modifying the matrix associated with the interpretation model. This procedure in general leads to overestimated depths which are corrected through the expression of the anomaly of a Bou...

Research paper thumbnail of Separation of PP and PS converted waves applied in mining exploration

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

This paper was prepared for presentation during the 16 th International Congress of the Brazilian... more This paper was prepared for presentation during the 16 th International Congress of the Brazilian Geophysical Society held in Rio de Janeiro, Brazil, 19-22 August 2019. Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Separation of PP‐ and PS‐wave reflected seismic data using two‐dimensional finite offset common‐reflection‐surface traveltime approximation

Geophysical Prospecting, 2020

Recently, the interest in PS‐converted waves has increased for several applications, such as sub‐... more Recently, the interest in PS‐converted waves has increased for several applications, such as sub‐basalt layer imaging, impedance estimates and amplitude‐versus‐offset analysis. In this study, we consider the problem of separation of PP‐ and PS‐waves from pre‐stacked multicomponent seismic data in two‐dimensional isotropic medium. We aim to demonstrate that the finite‐offset common‐reflection‐surface traveltime approximation is a good alternative for separating PP‐ and PS‐converted waves in common‐offset and common shot configurations by considering a two‐dimensional isotropic medium. The five parameters of the finite‐offset common‐reflection‐surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle, one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP‐ and PS‐converted waves were separated, the sections are stacked to increase the signal‐to‐noise ratio using the special curves derived from finite‐offset common‐reflection‐surface approximation. We applied this methodology to a synthetic dataset from simple‐layered to complex‐structured media. The numerical results showed that the inverted parameters of the finite offset common‐reflection‐surface and the separation function yield good results for separating PP‐ and PS‐converted waves in noisy common‐offset and common shot gathers.

Research paper thumbnail of Basement relief estimative of the Parnaíba basin´s west border through 2D gravity modelling

Proceedings of the 7 Simpósio Brasileiro de Geofísica, 2016

We present a gravity interpretation of the west border of the Parnaíba basin´s basement relief. T... more We present a gravity interpretation of the west border of the Parnaíba basin´s basement relief. The residual Bouguer anomaly produced by the basin was estimated through the information of the Moho depth and spectral analysis. We interpreted six profiles across the basin strike through 2D modelling. We obtained depths less than 2km indicating a shallow embasament compared to the main depocenter and the northeast border of the basin.

Research paper thumbnail of Regularization of P-P and P-S converted waves data through the FO-CRS traveltime approximation

Proceedings of the VIII Simpósio Brasileiro e Geofísica, 2018

We present a new method of regularization of seismic data using the finite offset common reflecti... more We present a new method of regularization of seismic data using the finite offset common reflection source (FO-CRS) traveltime approximation. This method fits curves of common reflection source to the reflection events and stacks all the amplitudes in a given aperture. The stacked amplitude, afterwards, is allocated to the time coordinate in the trace to be interpolated. We applied this method to three synthetic velocity models and the results showed the capability for regularizing converted seismic waves in stratified medium.

Research paper thumbnail of Automatic picking using coherence measurement and global optimization

Proceedings of the 16th International Congress of the Brazilian Geophysical Society&Expogef, 2019

Contents of this paper were reviewed by the Technical Committee of the 16 th International Congre... more Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.

Research paper thumbnail of Time-depth conversion using image ray and normal ray in the tau-p domain: application in synthetic data

14th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 3-6 August 2015, 2015

The time-depth seismic conversion is an important tool in seismic processing in order to obtain f... more The time-depth seismic conversion is an important tool in seismic processing in order to obtain friendly results to the interpreter. The achievement of these sections, in depth, can be accomplished by pre- and post-stacking migration and by ray tracing methods. The tracing of normal and image rays were the methodologies used in this work for such conversion. The image ray converts a post-stacked time-migrated section to depth domain using only an initial direction of propagation. The normal ray converts time-stacked sections into depth sections requiring a set of a priori initial directions, this initial set of directions is obtained by slant stack technique. The sections obtained by image ray tracing showed good accuracy in recovering the depth of reflectors. The sections obtained by normal ray tracing recovered, with great accuracy, the depth of reflectors as well as the good lateral continuity of the same.

Research paper thumbnail of Interpretação gravimétrica da Bacia do Recôncavo utilizando inversão não linear

12th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 15–18 August 2011, 2011

Research paper thumbnail of Application of PP and PS-waves separation: A case study of N4WS Carajás mineral ore, Pará, Brazil

Journal of Applied Geophysics, 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.

Research paper thumbnail of Interpretação gravimétrica do relevo do embasamento da Bacia de Taubaté através da inversão não linear com vínculo de suavidade

Proceedings of the 4 Simpósio Brasileiro de Geofísica, 2010

Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a ... more Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a opinião da SBGf ou de seus associados. É proibida a reprodução total ou parcial deste material para propósitos comerciais sem prévia autorização da SBGf.

Research paper thumbnail of Seismic velocity inversion using the FO-CRS stack in layered medium

14th International Congress of the Brazilian Geophysical Society & EXPOGEF, Rio de Janeiro, Brazil, 3-6 August 2015, 2015

Research paper thumbnail of Efficient gravity inversion of discontinuous basement relief

GEOPHYSICS, 2015

We have developed a gravity inversion method to estimate a discontinuous basement relief based on... more We have developed a gravity inversion method to estimate a discontinuous basement relief based on an extended version of Bott's method that allows variable density contrasts between sediments and basement, optimizes the modulus of the solution correction at each iteration, and provides for solution stabilization. Initially, we obtain a linear approximation stabilized by the total variation functional that correctly maps the horizontal positions of the existing high-angle faults but produced poor estimates of the basin depths. Subsequent iterations update the depth estimates toward the correct values, at the same time preserving the correct fault horizontal positions. Additionally, we stabilize each solution correction by the smoothness constraint without inverting any matrix. The method was substantially more efficient than the nonlinear method, which solves a system of linear equations by the conjugate gradient method at each iteration. For 3000 parameters, it is almost four times faster than the conjugate gradient, and this ratio increased with the number of parameters.

Research paper thumbnail of Análise da modelagem 2D de dados gravimétricos da Província Alcalina de Goiás utilizando os interpoladores de mínima curvatura e IDW

Revista Sítio Novo

Obter a delineação de corpos alcalinos é de extrema importância para o mapeamento geológico, pois... more Obter a delineação de corpos alcalinos é de extrema importância para o mapeamento geológico, pois auxilia futuros estudos de prospecção. Apresentamos neste trabalho uma interpretação da anomalia gravimétrica Registro do Araguaia, pertencente à Província Alcalina de Goiás, que é caracterizada por uma série de pequenas intrusões magmáticas alcalinas de características ultramáficas a félsicas. A gravimetria é um método geofísico que consegue delinear esses corpos devido aos altos contrastes de densidade entre as intrusões e as rochas encaixantes. Apliquei a modelagem direta em um perfil de cada mapa gravimétrico interpolado, um através da mínima curvatura e outro através do inverso da distância ponderada (IDW, da sigla em inglês). A interpretação gravimétrica do perfil interpolado pela mínima curvatura mostra dois corpos sendo um aflorante, enquanto que o perfil interpolado pelo IDW mostra um corpo com profundidade em relação à superfície de 16 m. O resultado referente ao IDW é o mai...

Research paper thumbnail of Separation of PP-and PS-wave reflected seismic data using two-dimensional finite offset common-reflection-surface traveltime approximation

Geophysical Prospecting, 2020

Recently, the interest in PS-converted waves has increased for several applications, such as sub-... more Recently, the interest in PS-converted waves has increased for several applications, such as sub-basalt layer imaging, impedance estimates and amplitude-versus-offset analysis. In this study, we consider the problem of separation of PP-and PS-waves from pre-stacked multicomponent seismic data in two-dimensional isotropic medium. We aim to demonstrate that the finite-offset common-reflection-surface traveltime approximation is a good alternative for separating PP-and PS-converted waves in common-offset and common shot configurations by considering a two-dimensional isotropic medium. The five parameters of the finite-offset common-reflection-surface are firstly estimated through the inversion methodology called very fast simulated annealing, which estimates all parameters simultaneously. Next, the emergence angle , one of the inverted parameters, is used to build an analytical separation function of PP and PS reflection separation based on the wave polarization equations. Once the PP-and PS-converted waves were separated, the sections are stacked to increase the signal-to-noise ratio using the special curves derived from finite-offset common-reflection-surface approximation. We applied this methodology to a synthetic dataset from simple-layered to complex-structured media. The numerical results showed that the inverted parameters of the finite offset common-reflection-surface and the separation function yield good results for separating PP-and PS-converted waves in noisy common-offset and common shot gathers.

Research paper thumbnail of Application of PP and PS-waves separation: A case study of N4WS Carajás mineral ore, Pará, Brazil.

The seismic methods are starting to be an essential tool in mining industry when the ore deposit ... more The seismic methods are starting to be an essential tool in mining industry when the ore deposit is located under a thick altered layer. The applicability of reflection and refraction seismic holds an importance in exploration surveys due to a great necessity to investigate higher depths, mainly if compressional and shear waves data are associated, then the separation of the two types of wave became necessary. We apply a new methodology of PP and PS separation based on the estimatives of the Finite Offset Common Reflection Surface (FO-CRS) attributes. The attributes estimates are performed using the Very Fast Simulated Annealing search-for inversion algorithm. Once the attributes are estimated we use them to build a separation filter, which is function of the polarization angle of the wave and the angle of the ray at the receiver. After the separation the sections were stacked in order to increase the signal-to-noise ratio. The method was applied in the so-called N4WS iron orebody, pertaining to the Mineral Province of Carajás, northern Brazil. We applied the separation in a modelled reflection dataset of the geophysical model of the target created from electrorresistivity and refraction seismic methods. The separation was performed in a common shot section and common offset sections in order to demonstrate the geometry independency of the methodology. The conclusions show that the filter could separate successfully PP and PS amplitudes from seismic sections.

Research paper thumbnail of Regularization of P-P and P-S converted waves data through the FO-CRS traveltime approximation

Anais do VII Simpósio Brasileiro de Geofísica, 2018

We present a new method of regularization of seismic data using the finite offset common... more We present a new method of regularization of seismic
data using the finite offset common reflection source (FOCRS) traveltime approximation. This method fits curves
of common reflection source to the reflection events and
stacks all the amplitudes in a given aperture. The stacked
amplitude, afterwards, is allocated to the time coordinate
in the trace to be interpolated. We applied this method to
three synthetic velocity models and the results showed
the capability for regularizing converted seismic waves in
stratified medium.

Research paper thumbnail of Interpretação Gravimétrica do Relevo do Embasamento da Bacia do Marajó

Research paper thumbnail of Interpretação gravimétrica do relevo do embasamento da Bacia de Taubaté através da inversão não linear com vínculo de suavidade

Este texto foi preparado para a apresentação no IV Simpósio Brasileiro de Geofísica, Brasília, 14... more Este texto foi preparado para a apresentação no IV Simpósio Brasileiro de Geofísica, Brasília, 14 a 17 de novembro de 2010. Seu conteúdo foi revisado pelo Comitê Técnico do IV SimBGf, mas não necessariamente representa a opinião da SBGf ou de seus associados. É proibida a reprodução total ou parcial deste material para propósitos comerciais sem prévia autorização da SBGf. ____________________________________________________________________ Abstract We present a gravity interpretation of the Taubaté basin basement relief. The residual Bouguer anomaly produced by the basin was estimated through a robust polynomial fitting method. We interpreted three gravity profiles across the basin strike using the smoothness constraint. We obtained average estimated basement depths between 370 m and 940 m, indicating a very shallow basement.

Research paper thumbnail of Automatic velocity estimative through Finite Offset Common Reflection Source (FO- CRS)

The development of seismic exploration is essentially based on the understanding of subsurface ve... more The development of seismic exploration is essentially based on the understanding of subsurface velocity field, so the estimated velocities and depths in a geological environment is an important stage in processing and interpretation of seismic data. The methodology used in this work is based on the use of the inversion of consistency, which is to maximize the semblance function, calculated from pre-stack seismic data, in order to obtain information about the velocities in the subsurface. We present a study about the sensitivity of the semblance function with respect to variation of the FO-CRS parameters (finite-offfset common-reflection-surface) on reflection events from CMP gathers (common mid-point). The results obtained with synthetic data, with and without noise, show values very close to those adopted in the model, indicating the reliability of the FO-CRS approach in the inversion process.