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Seismic Detection and Delineation of a Low Q Structure
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 78th EAGE Conference and Exhibition 2016, May 2016, Volume 2016, p.1 - 5
Abstract
A highly localized and extremely low Q is detected through multiple measurements from seismic datasets acquired for mineral exploration in the Athabasca Basin, Canada. Q estimation methods used are time-domain amplitude decay, frequency-domain spectrum ratio, and velocity dispersion. The results confirm that locally Q can be smaller than 10, which is lower than all the values reported for marine and land seismic exploration datasets associated with either gas anomalies or volcanic studies. The very strong attenuation of seismic waves in the Athabasca Basin was previously assumed to occur because of the overburden. However, low Q observed over the entire borehole extent indicates it reflects deep rock anelastic properties. We have also discovered an azimuth-dependent nature of both the velocity and Q through the analyses of the manually picked first break traveltimes and waveforms from the surface data. Variations of velocity appear to be primarily affected by the local topography while behaviours of Q reflect deeper features such as fault zones and fault associated alterations. Such environments are challenging for seismic imaging as the signal-to-noise ratio is strongly reduced. However, low-Q zones may be footprint indicator.