Multifold ground-penetrating radar and resistivity to study the stratigraphy of shallow unconsolidated sediments (original) (raw)

The leading edge, 2003

Abstract

Reconstruction of shallow stratigraphy of unconsolidated sediments is a topic of primary interest in several environmental, hydrological, geotechnical, and engineering applications. The identification of porous layers and the assessment of their saturation, the characterization of sediments, the identification of bedrock and the analysis of shallow layering are some examples of topics of primary interest in near-surface applications. Recent ground-penetrating radar (GPR) research demonstrates the excellent results that can be attained in the study of shallow stratigraphy. Complex stratigraphic structures, involving cross-stratification, conflicting dips, and rapid lateral and vertical particle-size variations pose a challenge to the application of single-fold (constant offset) GPR methods. The objectives of the present work are imaging and resolution enhancement of GPR multifold records from shallow, unconsolidated sediments. The study is based, in particular, on prestack processing and imaging of data from alluvial plain sites in northern Italy, which are characterized by different stratigraphic and sedimentological conditions. Figure 1 shows the location map of the survey. We show the results obtained on a fluvial terrace of the Isonzo River that are characterized by a complete alluvial sequence including a range of sediments (gravel to clayey loam) and range of stratigraphic structures (depositional and erosional). The water table and vadose zone are in the GPR and resistivity depth range and affect the response of the geophysical techniques, particularly the lateral and vertical resistivity and GPR velocity variations. Figure 1. Map and aerial picture of the study area. The red rectangle shows the location of the 20 × 12 m study area. The site is close to the riverbank, where the different stratigraphic units identified by the geophysical survey were identified and sampled. A Mala Geoscience GPR system was equipped with shielded 250-MHz antennae for the study. Single-fold methods were used in reconnaissance surveys at all test sites. We successively performed …

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