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Two-dimensional shallow soil profiling using time-domain waveform inversion

Mohamed Amrouche and Hiroaki Yamanaka
Two-dimensional shallow soil profiling using time-domain waveform inversion
Geophysics (2015) 80 (1): EN27-EN41

Abstract

Near-surface characterization has now gained significance among exploration geophysicists, and many methods are being proposed to retrieve the 2D structures of shallow soils. Because most of these methods are based on the modal inversion of the surface waves, they can only be applied to laterally homogeneous or smoothly heterogeneous soil models. We have developed a time-domain waveform inversion method for 2D near-surface exploration that offers an alternative approach to existing surface-wave techniques for layered soils with a flat surface. Our method directly fits the input Rayleigh waveforms to retrieve the 2D soil structure without need of any modal identification, allowing the inversion of soil models that can be challenging with modal-inversion-based approaches. In our method, the forward problem formulated in the time domain is based on a 2.5D staggered-grid finite-difference scheme to simulate the P-SV wavefield; soil modeling was achieved by dividing soil layers into specific number of blocks with discontinuous interfaces. The inversion strategy depends on attributing suitable values for the interface depth and S-wave velocity for each block to reconstruct a numerical soil model that fit the input waveforms. Because we cannot know the source signature during data acquisition, source deconvolution by a reference station is applied to observed and calculated waveforms to make a waveform inversion free of the source signature. Numerical experiments revealed that our method was able to sufficiently reconstruct soil structures with strong lateral velocity gradient or soils with a blind layer in noisy environments, using a single source and reasonable number of receivers. We also applied this method to real waveform data, and we succeeded in obtaining good correlation between the inverted 2D soil model and the existing borehole data.


ISSN: 0016-8033
EISSN: 1942-2156
Coden: GPYSA7
Serial Title: Geophysics
Serial Volume: 80
Serial Issue: 1
Title: Two-dimensional shallow soil profiling using time-domain waveform inversion
Affiliation: Tokyo Institute of Technology, Department of Environmental Science and Technology, Yokohama, Japan
Pages: EN27-EN41
Published: 2015
Text Language: English
Publisher: Society of Exploration Geophysicists, Tulsa, OK, United States
References: 39
Accession Number: 2015-026546
Categories: Applied geophysicsSoils
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. 3 tables
N35°04'60" - N35°40'00", E138°55'00" - E139°45'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by Society of Exploration Geophysicists, Tulsa, OK, United States
Update Code: 201513
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