HR: 0800h
AN: T21A-0447    [Abstracts]
TI: Application of Fresnel-Volume-Migration to the SAFOD2003 Data set
AU: * Buske, S
EM: buske@geophysik.fu-berlin.de
AF: Free University of Berlin, Institute of Geological Sciences, Malteserstr. 74-100, Berlin, 12249 Germany
AB: We present the application of 3D Fresnel-Volume-Migration (FVM) to a shot gather of the SAFOD2003 active seismic reflection survey. FVM is an extension of Kirchhoff prestack depth migration (KPSDM). The basic idea is to restrict the imaging procedure to the physical relevant part of the subsurface within the final step of transforming the seismic data from time to depth. Conventional KPSDM distributes the recorded wavefield along the corresponding two-way traveltime isochrons. An image is generated by constructive interference of these isochrons along the actual reflector elements. This method is considered as a state-of-the-art technique in obtaining high-quality images of the subsurface. However in the case of sparse sampling or limited aperture the resulting image is mostly affected by significant migration noise due to the less constructive interference of the backpropagated wavefield. Here we use the concept of Fresnel-Volumes to restrict the migration operator in a physically frequency-dependent way. The emergence angle at the receiver is determined from a local slowness analysis. Using this emergence angle as the starting direction a ray is propagated into the subsurface and the backpropagation of the wavefield is restricted to the vicinity of this ray according to its approximated Fresnel-Volume. This procedure resolves the spatial ambiguity and results in strongly reduced migration artefacts. Furthermore, steeply dipping events as well as flat reflectors are treated in the same way and no a-priori knowledge or processing is required to enhance either of them. Along with an introduction to the principles and the implementation of FVM this talk presents mainly the results of applying FVM to a single shot gather of the SAFOD2003 survey. Compared to the image obtained by KPSDM the FVM clearly shows a bunch of steeply dipping reflectors, which probably correspond to the San-Andreas-Fault system. In addition horizontally oriented structures are also visible at intermediate depths. The obtained image may serve as a basis for a more detailed future geological interpretation.
DE: 0935 Seismic methods (3025, 7294)
DE: 3285 Wave propagation (0689, 2487, 4275, 4455, 6934)
DE: 7260 Theory
DE: 8010 Fractures and faults
DE: 8150 Plate boundary: general (3040)
SC: Tectonophysics [T]
MN: Fall Meeting 2005