HR: 0830h
AN: NS41B-01    [Abstracts]
TI: Improved Characterization of the Shallow Subsurface by Nonlinear AVA Analysis of High-Resolution Seismic Data
AU: * Slob, E
EM: e.c.slob@citg.tudelft.nl
AF: Delft University of Technology, Department of Geotechnology, Mijnbouwstraat 120, Delft, 2628 RX Netherlands
AB: The focus of high-resolution shallow seismic has so far been on obtaining the geometrical or the structural information of the subsurface. Estimation of soil properties from surface seismic data has remained restricted to some spatially average values. However, it is the local properties, and not the average properties, that are more meaningful to the geotechnical, civil and environmental engineers. Laboratory estimation of soil properties, especially shear modulus and density, usually suffers from sample disturbance, and in-situ estimates are hard to obtain in loose, soft soils. The recent developments in data acquisition and processing technology provide the opportunity to extract soil information using the amplitude of shallow seismic reflections. Our research to extract the detailed soil information combines a reliable macro velocity model derived from seismic reflection data with the local interfacial velocity information obtained from angle-versus-amplitude (AVA) inversion. The approach first decomposes the multi-component data into P- and S- waves, which are then processed separately. Local density fluctuations are also estimated. The final model contains fine details that cannot be revealed by conventional velocity analysis. Our research shows that for large incidence angles and sharp velocity and density contrasts, which typify transitions in the shallow subsoil, a full nonlinear AVA inversion is essential for reliable local property estimation. The new approach has been tested on both synthetic and real data. The detailed information obtained can be translated to soil properties relevant to the engineers.
DE: 5102 Acoustic properties
DE: 5114 Permeability and porosity
SC: Near-Surface Geophysics [NS]
MN: 2005 Joint Assembly