Reconstruction of shallow subsurface structure from geophysical data is a central problem for many environmental and engineering applications. We observe that for shallow soil distributions, seismic data alone or electrical data alone may provide a good reconstruction of the subsurface. We show that using joint seismic and electrical data will improve the reconstruction of shallow structure. Our results emphasize that the availability of techniques for making laboratory measurements of ultrasonic velocities at low pressures in unconsolidated materials and the ability to measure complex impedance in similar samples are key elements of this approach.

Lead Principal Investigator: Patricia A. Berge (LLNL, PO Box 808, MS L-221, Livermore, CA 94551; 925-423-4829; berge1@llnl.gov) Co-Investigators: Brian P. Bonner (LLNL, PO Box 808, MS L-201, Livermore, CA 94551; 925-422-7080; bonner1@llnl.gov) Jeffery J. Roberts (LLNL, PO Box 808, MS L-201, Livermore, CA 94551; 925-422-7108; roberts17@llnl.gov) Contributors (LLNL unless otherwise indicated): Research ObjectiveOur goal is to improve geophysical imaging of the vadose zone. We are achieving this goal by providing new methods to improve interpretation of field data. The purpose of this EMSP project is to develop relationships between laboratory measured geophysical properties and porosity, saturation, and fluid distribution, for partially saturated soils. Algorithms for relationships between soil composition, saturation, and geophysical measurements will provide new methods to interpret geophysical field data collected in the vadose zone at sites such as Hanford, WA.