Improved structural characterization of the Earth's crust at the German Continental Deep Drilling Site using advanced seismic imaging techniques

F Hloušek, O Hellwig, S Buske - Journal of Geophysical …, 2015 - Wiley Online Library
F Hloušek, O Hellwig, S Buske
Journal of Geophysical Research: Solid Earth, 2015Wiley Online Library
This paper describes the principles of three novel seismic imaging techniques and their
application to two deep seismic reflection data sets from the vicinity of the German
Continental Deep Drilling Site (KTB). These imaging techniques are based on Kirchhoff
prestack depth migration and use an inherent restriction of the migration operator to focus
the wavefield to its actual reflection point. For Fresnel volume migration, the emergent angle
at the receivers is estimated and then used to propagate the wavefield back into the …
Abstract
This paper describes the principles of three novel seismic imaging techniques and their application to two deep seismic reflection data sets from the vicinity of the German Continental Deep Drilling Site (KTB). These imaging techniques are based on Kirchhoff prestack depth migration and use an inherent restriction of the migration operator to focus the wavefield to its actual reflection point. For Fresnel volume migration, the emergent angle at the receivers is estimated and then used to propagate the wavefield back into the subsurface along which the Fresnel volume is determined. The migration operator is restricted to this volume, thereby focusing the image to the part of the isochrone which physically contributes to the reflection. For coherency migration, the coherency of the wavefield at neighboring traces is calculated and used as a weighting factor within the migration integral, leading to a comparable focusing to the reflection point. For coherency‐based Fresnel volume migration, both approaches are combined, resulting in an even more focused seismic image with significantly increased image quality. We applied these methods to two seismic data sets from the area around the KTB: a survey with standard split‐spread geometry (KTB8502) and a sparse data set with a small number of source points in combination with short receiver lines (INSTRUCT93). The focusing approaches yield major improvements in the final images for both data sets. Incoherent noise and migration artifacts are reduced and the visibility of crustal structures is strongly enhanced, allowing for an improved geologic and tectonic characterization.
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