Crust and upper mantle Q from seismic refraction data: Peace River region

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Zelt, C. A., Ellis, R. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1990
• Subjects: General Earth and Planetary Sciences; Canada; Peace River
• Online Access: http://dx.doi.org/10.1139/e90-108; http://www.nrcresearchpress.com/doi/pdf/10.1139/e90-108

Crustal refraction data from the Peace River region of Alberta, Canada, have been analyzed using the spectral ratio method to obtain Q. A total of 1205 first and later arrivals corresponding to turning and reflected P-waves within the crust and upper mantle were studied. Source spectra were estimated from near-offset traces assuming typical sedimentary Q values. The large scatter of measured spectral ratios restricted the resolution to a three-layer model of the crust and upper mantle with Q constant in each layer. This model was obtained using a linear inverse method since the measured spectral ratios and known traveltimes in each layer are linearly related through the attentuation (Q −1 ) in each layer. A weighted L 1 norm was minimized using linear programming, the weights being a measure of the certainty of each spectral ratio. The inversion was performed using the 25% most certain spectral ratios, regardless of magnitude or sign. Model bounds taking account of the scattered data were estimated. The results suggest that Q is between 200 and 500 in the upper crust and greater than 600 in the lower crust and upper mantle. This model is generally consistent with Q obtained from studies on nearby crust.