Rayleigh wave anelastic attenuation across the Bermuda Rise and the volcanic Caribbean Arch

• Published in: Geophysical Journal International
• Main Author: Canas, José A.
• Format: Text
• Language: English
• Published: Oxford University Press 1982
• Subjects: Articles; Pacific; North Atlantic
• Online Access: http://gji.oxfordjournals.org/cgi/content/short/71/3/703; https://doi.org/10.1111/j.1365-246X.1982.tb02793.x

Average fundamental mode group velocities and attenuation coefficients of Rayleigh waves have been obtained in a region of the Western North Atlantic comprising the Bermuda Rise, the volcanic Caribbean Arch, and normal seafloor greater than 65 Myr in age. The average Rayleigh wave attenuation coefficients decrease from a value of 7.78 × 10-4 km-1 at a period of 15s to a value of 0.21 × 10-4 km-1 at a period of 100 s. Attenuation values and Q R factors obtained are characteristic of a young oceanic region, and they do not correspond to a typical region greater than 65 Myr in age. It is apparent from the data that the high attenuation values reported are due to the effect that the back-arc basin behind the Caribbean Arch has on Rayleigh wave attenuation. Inversion theory applied to the attenuation data yields a Q -1 β model presenting the same features as those corresponding to extension zones such as the spreading centres of the Atlantic and Pacific Oceans. The low-Q region in the model is situated between depths of around 15 and 100 km, with the maximum Q -1 β value (∼17 × 10-3)occurring at about 50 km depth.