Coda Q estimates in the Mount Cameroon volcanic region, West Africa

Coda Q , Qc , has been determined in the Mount Cameroon volcanic region, West Africa, from the decay of the amplitudes of coda waves on narrow band-pass-filtered seismograms of local microearthquakes in the frequency range 1.5 to 24 Hz. Qc averages about 121 and 1745 at 1.5 Hz and 24 Hz, respectively, and has a frequency dependence of the form Qc = 65f. For each frequency band, the coda Q values, averaged over all the earthquakes, show an insensitivity to the compoment of the ground motion. Considering a model incorporating both scattering and intrinsic attenuation, and assuming that the attenuation is entirely due to the scattering loss, a frequency-independent minimum mean free path of about 38 km was found.