HR: 11:20h
AN: S12A-05    [Abstracts]
TI: Dip Corrections for Seismic Reflection Velocity Analysis
AU: * Gunther, R
EM: rgunther@stanford.edu
AF: Stanford University, Department of Geophysics, 397 Panama Mall, Mitchell Building 360, Stanford, CA 94309, United States
AU: Reshef, M
EM: moshe@luna.tau.ac.il
AF: Tel Aviv University, Department of Geophysics and Planetary Sciences, Tel Aviv, 69978, Israel
AB: We use structural dip information to mitigate noise in time processing of active-source seismic reflection data, especially in land or low-fold marine datasets characterized by low signal-to-noise ratios (SNR). We estimate dip fields in stacked sections using robust iterative semblance scans. In two-dimensional data, the dip fields consist of single time-dip components defined at each image point; in three-dimensional data, the fields consist of simultaneously constrained in-line and cross-line dip components. The dip fields are used as input for a Common Reflection Surface (CRS) stack that sums along move-out curves in both the midpoint and offset dimensions to create sections with improved SNR. We show that this process is equivalent to a post-stack local slant stack that trades along-dip resolution for noise suppression. Dip fields are also used for velocity analysis in super-gathers, groupings of adjacent common midpoint (CMP) gathers commonly used for velocity analysis. We use the CRS travel-time formulae to correct for differences in zero-offset travel-times for traces with different midpoints within the super-gather. The corrections supplement dip move-out (DMO), which corrects for multiple conflicting dips in traces within a single CMP gather. While DMO collapses semblance maxima from conflicting dips into a single maximum, our dip corrections increase the sharpness of the peaks and make the semblance panels easier to interpret. As a result, larger super-gathers with more traces can be used to increase SNR without blurring the semblance maxima. We then apply the same technique to residual move-out (RMO) analysis using dip fields computed on migrated sections. Super-gathers are also commonly used for computing for RMO semblance panels, so the dip corrections similarly lead to sharper maxima and facilitate the use of larger gathers. Examples are shown for both 2D and 3D datasets.
DE: 0902 Computational methods: seismic
DE: 0910 Data processing
DE: 0935 Seismic methods (3025, 7294)
DE: 3025 Marine seismics (0935, 7294)
SC: Seismology [S]
MN: 2007 Fall Meeting