Improvements in crosshole GPR full-waveform inversion and application on data measured at the Boise Hydrogeophysics Research Site

Abstract Crosshole ground penetrating radar (GPR) tomography has been widely used and has the potential to improve the obtained subsurface models due to its high spatial resolution compared to other methods. Recent advances in full-waveform inversion of crosshole GPR data show that higher resolution images can be obtained compared to conventional ray-based GPR inversion because it can exploit all information present in the observed data. Since the first application of full-waveform inversion on synthetic and experimental GPR data, the algorithm has been significantly improved by extending the scalar to a vectorial approach, and changing the stepped permittivity and conductivity update into a simultaneous update. Here, we introduce new normalized gradients that do not depend on the number of sources and receivers which enable a comparison of the gradients and step lengths for different crosshole survey layouts. An experimental data set acquired at the Boise Hydrogeophysics Research Site is inverted using different source–receiver setups and the obtained permittivity and conductivity images, remaining gradients and final misfits are compared for the different versions of the full-waveform inversion. Moreover, different versions of the full-waveform inversion are applied to obtain an overview of all improvements. Most improvements result in a reducing final misfit between the measured and synthetic data and a reducing remaining gradient at the final iteration. Regions with relatively high remaining gradient amplitudes indicate less reliable inversion results. Comparison of the final full-waveform inversion results with Neutron–Neutron porosity log data and capacitive resistivity log data show considerably higher spatial frequencies for the logging data compared to the full-waveform inversion results. To enable a better comparison, we estimated a simple wavenumber filter and the full-waveform inversion results show an improved fit with the logging data. This work shows the potential of full-waveform inversion as an advanced method that can provide high resolution images to improve hydrological models.

[1]  W. Barrash,et al.  Hierarchical geostatistics and multifacies systems: Boise Hydrogeophysical Research Site, Boise, Idaho , 2002 .

[2]  Tom Clemo,et al.  Boise Hydrogeophysical Research Site (Bhrs): Objectives, Design, Initial Geostatistical Results , 1999 .

[3]  Baptiste Dafflon,et al.  Three‐dimensional stochastic estimation of porosity distribution: Benefits of using ground‐penetrating radar velocity tomograms in simulated‐annealing‐based or Bayesian sequential simulation approaches , 2012 .

[4]  W. Barrash,et al.  Significance of porosity for stratigraphy and textural composition in subsurface, coarse fluvial deposits: Boise Hydrogeophysical Research Site , 2004 .

[5]  Jean Virieux,et al.  An overview of full-waveform inversion in exploration geophysics , 2009 .

[6]  Michael D. Knoll,et al.  Capacitive conductivity logging and electrical stratigraphy in a high-resistivity aquifer, Boise Hydrogeophysical Research Site , 2009 .

[7]  P. Dietrich,et al.  Integrating surface georadar and crosshole radar tomography: A validation experiment in braided stream deposits , 2002 .

[8]  Andrew Binley,et al.  Monitoring Unsaturated Flow and Transport Using Cross‐Borehole Geophysical Methods , 2008 .

[9]  W. P. Clement,et al.  Crosshole Radar Tomography in a Fluvial Aquifer Near Boise, Idaho , 2006 .

[10]  Niklas Linde,et al.  Full-waveform inversion of cross-hole ground-penetrating radar data to characterize a gravel aquifer close to the Thur River, Switzerland , 2010 .

[11]  Jacques R. Ernst,et al.  Application of a new 2D time-domain full-waveform inversion scheme to crosshole radar data , 2007 .

[12]  A. Tarantola.  Inversion of seismic reflection data in the acoustic approximation , 1984 .

[13]  James Irving,et al.  Inversion of Multiple Intersecting High-Resolution Crosshole GPR Profiles for Hydrological Characterization at the Boise Hydrogeophysical Research Site , 2011 .

[14]  R. Pratt.  Frequency-domain elastic wave modeling by finite differences : a tool for crosshole seismic imaging , 1990 .

[15]  Hansruedi Maurer,et al.  Taming the non-linearity problem in GPR full-waveform inversion for high contrast media , 2011 .

[16]  Martin Musil,et al.  Effects and removal of systematic errors in crosshole georadar attenuation tomography , 2004 .

[17]  H. Maurer,et al.  Ray-based amplitude tomography for crosshole georadar data: a numerical assessment , 2001 .

[18]  D. Gomez,et al.  Flow and transport in the unsaturated Sherwood Sandstone: characterization using cross-borehole geophysical methods , 2006, Geological Society, London, Special Publications.

[19]  A. P. Annan,et al.  Electromagnetic Determination of Soil Water Content: Application of TDR to Field Measurements , 1980 .

[20]  John H. Bradford,et al.  Estimating porosity with ground‐penetrating radar reflection tomography: A controlled 3‐D experiment at the Boise Hydrogeophysical Research Site , 2009 .

[21]  Andrew Binley,et al.  High‐resolution characterization of vadose zone dynamics using cross‐borehole radar , 2001 .

[22]  James Irving,et al.  Evaluation of the reconstruction limits of a frequency-independent crosshole georadar waveform inversion scheme in the presence of dispersion , 2012 .

[23]  Susan S. Hubbard,et al.  Ground‐penetrating‐radar‐assisted saturation and permeability estimation in bimodal systems , 1997 .

[24]  Andrew Binley,et al.  Electrical imaging of saline tracer migration for the investigation of unsaturated zone transport mechanisms. , 1997 .

[25]  Alberto Villa,et al.  An experiment of non‐invasive characterization of the vadose zone via water injection and cross‐hole time‐lapse geophysical monitoring , 2007 .

[26]  A. Tarantola.  A strategy for nonlinear elastic inversion of seismic reflection data , 1986 .

[27]  Erwan Gloaguen,et al.  Estimation of hydraulic conductivity of an unconfined aquifer using cokriging of GPR and hydrostratigraphic data , 2001 .

[28]  R. Knight,et al.  Improving crosshole radar velocity tomograms: A new approach to incorporating high-angle traveltime data , 2007 .

[29]  James Irving,et al.  Analysis of an iterative deconvolution approach for estimating the source wavelet during waveform inversion of crosshole georadar data , 2012 .

[30]  R. Pratt.  Seismic waveform inversion in the frequency domain; Part 1, Theory and verification in a physical scale model , 1999 .

[31]  Jacques R. Ernst,et al.  Full-Waveform Inversion of Crosshole Radar Data Based on 2-D Finite-Difference Time-Domain Solutions of Maxwell's Equations , 2007, IEEE Transactions on Geoscience and Remote Sensing.

[32]  R. Knight,et al.  Effect of antennas on velocity estimates obtained from crosshole GPR data , 2005 .

[33]  S. Greenhalgh,et al.  Crosshole seismic inversion with normalized full‐waveform amplitude data , 2003 .

[34]  A. P. Annan,et al.  Electromagnetic determination of soil water content: Measurements in coaxial transmission lines , 1980 .

[35]  Harry Vereecken,et al.  Optimization of acquisition setup for cross-hole GPR full-waveform inversion using checkerboard analysis , 2013 .

[36]  A. Binley,et al.  Vadose zone flow model parameterisation using cross-borehole radar and resistivity imaging , 2001 .

[37]  Michael D. Knoll,et al.  Multivariate analysis of cross‐hole georadar velocity and attenuation tomograms for aquifer zonation , 2004 .

[38]  Jacques R. Ernst,et al.  A New Vector Waveform Inversion Algorithm for Simultaneous Updating of Conductivity and Permittivity Parameters From Combination Crosshole/Borehole-to-Surface GPR Data , 2010, IEEE Transactions on Geoscience and Remote Sensing.

[39]  A. Binley,et al.  Improved hydrogeophysical characterization using joint inversion of cross‐hole electrical resistance and ground‐penetrating radar traveltime data , 2006 .

[40]  M. Worthington,et al.  Resolution limits in ray tomography due to wave behavior: Numerical experiments , 1993 .

[41]  Harry Vereecken,et al.  Crosshole GPR full-waveform inversion of waveguides acting as preferential flow paths within aquifer systems , 2012 .