High-resolution 3-D multi-component seismics for an improved structural, facial, and process-related characterisation of glacially overdeepened valleys and basins in the Alps

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The integration of high-resolution three-dimensional (3-D) and multi-component seismics for an improved structural, facial, and process-related characterization of overdeepened valleys and basins defines the principal aim and scientific-technical approach of this project. Overdeepened structures are known from formerly glaciated areas worldwide. They have important impact on both applied and basic aspects of human life and research. Highly topical issues are groundwater exploration, geohazard potential (site effects, mass movements), and geo-engineering (nuclear waste repositories, tunnelling). The sediments in overdeepened structures also provide important information about timing and extent of past glaciations. These aspects require a profound knowledge of the sediment fill and valley genesis, tackled by the ICDP initiative Drilling Overdeepened Alpine Valleys (DOVE) with boreholes to be cored at key locations in the European Alps. To create an exemplary and transferable seismic workflow for geological depth model building, a systematic reflection seismic research study will be performed in the Tannwald (Germany) and Lienz Basins (Austria) which will be representative of overdeepened structures in the Alpine foreland and the inner-Alpine area. The methodological work will especially contribute to an improved mapping of the valley shapes, a more detailed and facies-based interpretation of the sedimentary infill, the interpretation of glaciotectonic features, and the spatial and temporal process understanding of overdeepened valley development and its recent consequences. Advanced survey designs allow to derive comprehensive petrophysical parameter sets to support geological interpretation, and most importantly, not restricted to 1-D information in a borehole but with spatial extent. The limitations of classical P-wave seismics will be overcome by an innovative and combined field-acquisition and processing scheme that makes use of the development of new seismic sources designed for the exploration of near-surface structures, consolidated experience with S-wave reflection seismics, and new opportunities provided by multi-component seismics. Here, we suggest consecutive seismic surveys that use P- and S-wave sources on the one hand, combined with 3-component (3-C) receivers on the other hand. Thereby, so-called 9-C surveying is finally possible, concerted on 2-D profiles and in 3-D. This will satisfy, for the first time, the challenging demands of imaging overdeepened structures in terms of (near-surface) complexity, small rock physical contrasts, and anisotropy. Accompanying seismic modelling will contribute a deeper understanding of the nature of reflections gained and will provide insight into the wavefields characteristics to better understand the geophysical properties of overdeepened structures. A local, target-oriented multi-component 3-D survey focusing on wave-propagation effects in shallow structures will complete this systematic study.