oa Seismic imaging at a mineral-deposit scale using high-frequency surface waves (0.5–24 Hz) in ambient noise wavefield

Ambient noise, surface-wave tomography (ANSWT) is now a routine technique for imaging crustal and upper mantle structure at a regional scale. Its cost efficiency and environmental friendliness also make ANSWT an attractive method for mineral exploration. However, the application of the technique in mineral exploration requires the retrieval of wide-band, high-frequency surface waves from seismic noise, so as to obtain high-resolution images of shallow structures. We present a new workflow optimized to extend the bandwidth of high-frequency surface waves retrieved. It comprises short time-window stacking, cross-coherence and an improved phase velocity measurement method. We tested the workflow on data from a large-N array over a Cu-PGE deposit in Ontario, Canada, and successfully measured phase velocities for numerous inter-station pairs in a broad frequency ranges from 0.55 Hz to 23.8 Hz. Analysis of the phase velocity maps reveals a west-dipping high-velocity anomaly that matches the west-dipping, multi-staged gabbro intrusions associated with the deposit.