Seismic raytracing method and apparatus

Abstract

A seismic ray-tracing model performs economic exploration of subsurface structures, which 1) allows amplitude, frequency, mode, and other 'synthetic filtering' of the model's calculations and 2) allows model interpolations, approximations, and other 'synthetic sensitivity' terminations of ray-tracing calculations. The model output can be directly matched to the filtration and sensitivity of actual seismic data. The model structure is capable of the extensive calculations similar to current extensive forward models, but ray-tracing calculations are accomplished in discrete pairs (allowing interpolation between divergent ray pairs and partially simulating detector sensitivity) and ray-tracing calculations are terminated if an amplitude under a threshold level signal strength is encountered. The amplitude threshold level can be set to match filtering used on actual seismic data. This sensitivity and filter matching achieves maximum reliability while still avoiding unnecessary calculations, e.g., avoids redundant single ray calculations and calculations which produce synthetic signals below the filtered sensitivity of the recording instrument. The present invention can also limit and control mode conversions (further speeding calculations), include a time-domain absorption operator dependant only on the wave path and wave mode, allow perturbation modeling, and can specifically identify each event in the synthetic signals via color coded graphics and/or a printed list referenced by apparent velocity (V.sub.RMS) and zero-offset intercept time.