oa Super-Virtual Refraction Interferometric Redatuming: Enhancing the Refracted Energy

Complex near surface is one of the main challenges for onshore seismic data processing. Refraction tomography is becoming a common way to estimate an accurate near surface velocity model. One of the problems with refraction tomography is the low signal to noise ration in far offset data.

To improve, we propose using super-virtual refraction interferometry to enhance the weak energy at far offsets.

We use Interferometric Green’s functions to redatum sources by cross-correlating two traces recorded at receiver stations, A and B, from a source at location W. The result is a redatumed trace with a virtual source at A and a receiver at B, which can also be obtained by correlating two traces recorded at A and B from different shots. Stacking them would enhance the signal-to-noise ratio of this “virtual” trace.

We next augment redatuming with convolution and stacking. The trace recorded at B from a virtual source at A is convolved with the original trace recorded at A from a source at W. The result is a “super-virtual” trace at B in the far-offset from a source at W. Stacking N traces gives a √N-improvement.

We applied our method to noisy synthetic and field data recorded over a complex near-surface and we could pick more traces at far offsets. It was possible to accommodate more picks resulting in a better subsurface coverage.