Fiama, S.B., Mavonga, G.T., Rusangiza, K., Kervyn, F. & Delvaux, D. 2017. ‘Seismic attenuation of Coda waves in the volcanic area of Virunga, Occidental Branch of the East African Rifts System: Preliminary Results’. D. Delvaux, C. Michellier, O. Dewitte (eds), Geo-Eco-Trop 41/2, special issue : Geohazards in the Great Lakes Region of Central Africa : 187-203. Tervuren : Africa Museum. URL: http://www.geoecotrop.be/ (PR).
Article in a scientific Journal / Article in a Journal
333 volcano – tectonic earthquakes allowed to analyze the attenuation of the coda waves by the Single Scattering model in the Virunga region at the east of Democratic Republic of Congo. A high attenuation obtained by the quality factor Q_C or Q_0 of these waves illustrates a heterogeneous area dominated by scattering due to the presence of the magma in fractures. The weak values of Q_C are attributed to the loss of energy on the heterogeneities and the large ones at high frequencies (larger than 12 Hz) are due to the diffraction of the body waves through the deep lithosphere. The variation of attenuation parameters〖 Q〗_C, Q_0 and the frequency dependence n with the lapse time shows the differences between the heterogeneities or the magma properties with depth. The constancy of n between the lapse time of 30 – 60 s implies the conservation of heterogeneities dimensions with depth. The different values of Q_0 at each station could indicate site effects and a spatial temperature distribution due to the shallow magma intrusion. The high attenuation observed at BLG station suggests a fractured structure filled fluid (magma and/or water) at shallow depth.