Tomographic Inversion of Crosshole Radar Data: Confidence in Results

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. AUTHOR(S) ON REPRINT PERFORMING ORGANIZATION NAMES(S) AND ADDRESS(ES)Boise State University ABSTRACT Crosshole radar tomography is increasingly being used to characterize the shallow subsurface and to monitor hydrologic processes. Although tomographic inversion provides a subsurface model, confidently interpreting the resulting image can be challenging. We conducted a simple modeling study to better understand the capabilities and limitations of tomographic inversion. We start with a known earth model, simulate a tomography experiment, and invert the synthetic data. We investigate the effects of straight and curved ray approximations to wave propagation, regularization,grid size, and starting model. We also investigate the effects of limited ray coverage through the earth model and noise in the data. Understanding the effects of these different methods and parameterizations will help us place confidence limits on modeled features to more accurately reflect our knowledge of the subsurface.

The Use of Radar Methods to Determine Moisture Content in the Vadose Zone

“…Surface or borehole radar data can be used to obtain a model of the variation in the dielectric constant of the subsurface. Obtaining this dielectric model from surface and/or borehole data is a topic currently being addressed by other research groups (e.g., Cai and McMechan, 1999;Clement and Knoll, 2000;Tronicke et al, 2001;Holliger and Maurer, 2002), and was not an objective of our research. Our focus was on determining the optimal way to transform the 3-D map of dielectric constant κ into a 3-D map of water content θ.…”