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Recording Longer for Higher-Resolution Near-Surface Imaging - Shear-Wave Reflections from Vertical Sources and Receivers
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 25th European Meeting of Environmental and Engineering Geophysics, Sep 2019, Volume 2019, p.1 - 5
Abstract
Mode-converted reflections have long been recognized in field seismic data and have been used for improved imaging and targeting. However, their use for near-surface imaging and characterization have only been limited to dedicated SH-SH data acquisition setups. In a quick-clay landslide prone area in southwest Sweden, collocated SH-SH using 1 m source and receiver spacing, and a conventional P-wave line using 2 m source and receiver spacing were separately acquired using different instruments and setups. Both datasets have so far been the subject of several studies, however, only recently after recovering longer records of the P-wave data, clear hyperbolic events with slow moveouts were observed at 0.5 second and later times. Thanks to the long record and available SH-SH dataset, these reflections are interpreted to have pure shear-wave origin. Confirmed by downhole logging data and core observations and to some extent other independent geophysical datasets, the shear-wave reflection imaging of the perceived vertical component data, allowed two sets of coarse-grained layer materials and extremely undulating bedrock to be resolved. The P-wave reflection imaging of the dataset did not provide such a high-resolution image as obtained by the shear-wave reflection imaging given the strong source-generated noise at the very early arrivals.