Computation of coherence cube with variable time window length

Abstract

The coherence cube technology extracts the discontinuity attribute of the seismic events by analyzing the similarities of adjacent seismic channels. It has become an important technology for seismic interpretation. The conventional coherence cube technologies use constant time window lengths. But the frequency band of the seismic signal usually varies with depth, so such constant time window lengths can not balance the shallow layers and deep layers. When analyzing the shallow layers (having wide frequency band), the time window will crossover quite a few events, which will lead to weak focusing ability and failure to delineate the details. While the time window will not be long enough for analyzing deep layers (having low frequency band), which will lead to quite low accuracy because the coherences near the zero points of the events are heavily influenced by noise, and it is harmful for fault detection. This paper gives a coherence cube computing method with self-adaptively varying window lengths, which determines the sample points' time window lengths in real time by computing the instantaneous frequency bands with Gabor Transformation. The experiments for actual seismic data show that it can give accurate coherence in both deep and shallow layers.