The Experts below are selected from a list of 630 Experts worldwide ranked by ideXlab platform

Staal X.r. - One of the best experts on this subject based on the ideXlab platform.

  • Combined imaging and velocity estimation by Joint Migration Inversion
    2015
    Co-Authors: Staal X.r.
    Abstract:

    Seismic imaging projects aim to reveal the structure of the Earths Crust from seismic data. These projects typically include three separate processing steps, being: • attenuation of multiple reflections in the seismic data. • estimating seismic wave propagation velocities from the seismic data. • mapping the measured reflection data to the proper subsurface location by migration. In this thesis, we present a novel approach termed Joint Migration Inversion (JMI) that combines the estimation of seismic wave propagation velocities with the migration of seismic data. Additionally, JMI is capable of using multiple reflections to improve its velocity estimates and migration results, effectively removing the need to suppress multiple reflections in the seismic data. Joint Migration Inversion is posed as an inverse problem that solves for the subsurface parameters of reflectivity and velocity. This means that we use a forward model, termed Full Wavefield Modelling, that synthesizes seismic data based on a reflectivity model and a velocity model. We then we update the reflectivity model and velocity model until the synthesized data accurately matches the measured seismic data. Because Full Wavefield Modeling accounts for the nonlinear relationship between wavefields and reflectivity, leading to transmission effects and multiple scattering, the inversion scheme will automatically use these nonlinearities to optimise its reflectivity estimates as well as its velocity estimates. To update the reflectivity and velocity models JMI uses a gradient descent scheme, which is an iterative local optimisation algorithm. This thesis demonstrates the feasibility of Joint Migration Inversion by applying it to several numerically generated datasets, showcasing its ability to estimate kinematically accurate velocity models and to image the subsurface accurately in the presence of strong internal multiples and complex subsurface structures. We discuss the robustness of JMI, showing why we feel that the method will not suffer from cycle-skipping and that it will give accurate results given a wide variety of starting models. Finally, we present a case study where JMI is applied to a 2D section of a field dataset, showing the pre-processing steps required for a successful inversion and showing that JMI performs well on field data

  • Combined imaging and velocity estimation by Joint Migration Inversion
    2015
    Co-Authors: Staal X.r.
    Abstract:

    Seismic imaging projects aim to reveal the structure of the Earths Crust from seismic data. These projects typically include three separate processing steps, being: \u95 attenuation of multiple reflections in the seismic data. \u95 estimating seismic wave propagation velocities from the seismic data. \u95 mapping the measured reflection data to the proper subsurface location by migration. In this thesis, we present a novel approach termed Joint Migration Inversion (JMI) that combines the estimation of seismic wave propagation velocities with the migration of seismic data. Additionally, JMI is capable of using multiple reflections to improve its velocity estimates and migration results, effectively removing the need to suppress multiple reflections in the seismic data. Joint Migration Inversion is posed as an inverse problem that solves for the subsurface parameters of reflectivity and velocity. This means that we use a forward model, termed Full Wavefield Modelling, that synthesizes seismic data based on a reflectivity model and a velocity model. We then we update the reflectivity model and velocity model until the synthesized data accurately matches the measured seismic data. Because Full Wavefield Modeling accounts for the nonlinear relationship between wavefields and reflectivity, leading to transmission effects and multiple scattering, the inversion scheme will automatically use these nonlinearities to optimise its reflectivity estimates as well as its velocity estimates. To update the reflectivity and velocity models JMI uses a gradient descent scheme, which is an iterative local optimisation algorithm. This thesis demonstrates the feasibility of Joint Migration Inversion by applying it to several numerically generated datasets, showcasing its ability to estimate kinematically accurate velocity models and to image the subsurface accurately in the presence of strong internal multiples and complex subsurface structures. We discuss the robustness of JMI, showing why we feel that the method will not suffer from cycle-skipping and that it will give accurate results given a wide variety of starting models. Finally, we present a case study where JMI is applied to a 2D section of a field dataset, showing the pre-processing steps required for a successful inversion and showing that JMI performs well on field data.Imaging PhysicsApplied Science

Nenovski P. - One of the best experts on this subject based on the ideXlab platform.

  • Multi-point ground-based ULF magnetic field observations in Europe during seismic active periods in 2004 and 2005
    Copernicus Publications on behalf of the European Geosciences Union, 2008
    Co-Authors: Prattes G., Schwingenschuh K., Eichelberger H. U., Magnes W., Boudjada M., Stachel M., Vellante M., Nenovski P.
    Abstract:

    International audienceWe present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths Crust considering an average electrical conductivity of =10?3 S/m and a certain distance of the observatory to the earthquake epicenter

P. Nenovski - One of the best experts on this subject based on the ideXlab platform.

  • Multi-point ground-based ULF magnetic field observations in Europe during seismic active periods in 2004 and 2005
    Natural Hazards and Earth System Sciences, 2008
    Co-Authors: G. Prattes, Konrad Schwingenschuh, H. U. Eichelberger, Werner Magnes, M. Boudjada, M. Stachel, Massimo Vellante, Viktor Wesztergom, P. Nenovski
    Abstract:

    Abstract. We present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths Crust considering an average electrical conductivity of <σ>=10−3 S/m and a certain distance of the observatory to the earthquake epicenter.

Prattes G. - One of the best experts on this subject based on the ideXlab platform.

  • Multi-point ground-based ULF magnetic field observations in Europe during seismic active periods in 2004 and 2005
    Copernicus Publications on behalf of the European Geosciences Union, 2008
    Co-Authors: Prattes G., Schwingenschuh K., Eichelberger H. U., Magnes W., Boudjada M., Stachel M., Vellante M., Nenovski P.
    Abstract:

    International audienceWe present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths Crust considering an average electrical conductivity of =10?3 S/m and a certain distance of the observatory to the earthquake epicenter

G. Prattes - One of the best experts on this subject based on the ideXlab platform.

  • Multi-point ground-based ULF magnetic field observations in Europe during seismic active periods in 2004 and 2005
    Natural Hazards and Earth System Sciences, 2008
    Co-Authors: G. Prattes, Konrad Schwingenschuh, H. U. Eichelberger, Werner Magnes, M. Boudjada, M. Stachel, Massimo Vellante, Viktor Wesztergom, P. Nenovski
    Abstract:

    Abstract. We present the results of ground-based Ultra Low Frequency (ULF) magnetic field measurements observed from June to August 2004 during the Bovec earthquake on 12 July 2004. Further we give information about the seismic activity in the local observatory region for an extended time span 2004 and 2005. ULF magnetic field data are provided by the South European Geomagnetic Array (SEGMA) where the experience and heritage from the CHInese MAGnetometer (CHIMAG) fluxgate magnetometer comes to application. The intensities of the horizontal H and vertical Z magnetic field and the polarization ratio R of the vertical and horizontal magnetic field intensity are analyzed taking into consideration three SEGMA observatories located at different close distances and directions from the earthquake epicenter. We observed a significant increase of high polarization ratios during strong seismic activity at the observatory nearest to the Bovec earthquake epicenter. Apart from indirect ionospheric effects electromagnetic noise could be emitted in the lithosphere due to tectonic effects in the earthquake focus region causing anomalies of the vertical magnetic field intensity. Assuming that the measured vertical magnetic field intensities are of lithospheric origin, we roughly estimate the amplitude of electromagnetic noise in the Earths Crust considering an average electrical conductivity of <σ>=10−3 S/m and a certain distance of the observatory to the earthquake epicenter.