A review of the virtual refraction and application to active source crustal imaging

We present an overview of the spurious arrival in seismic interferometry called the virtual refraction. We find that this artifact is present in the crosscorrelated wavefields when refractions are present in the input data and can be used to characterize the subsurface velocity structure. In crustal seismic studies, refracted Pg and Pn phases are often used in a tomographic sense to create a subsurface velocity model that defines the geologic structure. We apply the virtual refraction analysis to the Continental Dynamics of the Rocky Mountains (CD-ROM) controlled source seismic data. In this analysis, we look at the effects of sparse data on the virtual refraction method and the super virtual refraction method, which incorporates an extra crosscorrelation of the wavefield, similar to source-receiver interferometry. We apply the virtual refraction technique with the intent to improve the signal-to-noise ratio of far offset recordings, as well as to better constrain the entire velocity model. The ultimate goal is to improve the current understanding of the geologic structure and evolution in the region.