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Seismic Imaging of Shallow Groundwater Resources in Glacial Deposits, Sweden
- 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
We re-process high-resolution shallow seismic reflection data collected over glacial deposits in Heby, Southeastern Sweden, to accurately map the dipping bedrock topographies and enhance the quality of the seismic images of groundwater bearing structures. We apply Kirchhoff pre-stack depth migration (PSDM) on the pre-stack processed data and compare our results with post-stack time migrated (PSTM) depth converted results. The velocity models calculated from first arrivals of shot gathers are used as initial models for travel time tomography. The velocity model estimated from the first-arrival tomography is used as a starting point for the pre- and post-stack migration. We observe that PSDM improves the seismic image. Especially reflections from the water table and dipping structures became prominent and continuous, and the reflectors are located more accurately, when borehole information is considered. The seismic image shows a water table around 35m elevation. The uppermost, about 20m overburden represents clay and constitutes sub-horizontal reflectors. This layer is underlain by sand/gravel deposits overlying the undulated bedrock. Our work shows that PSDM can help to obtain reliable near-surface images, contributing to reliable and sustainable groundwater management.