Fiama, S.B., Mavonga, G.T., Subira, J.M., Kervyn, F. & Delvaux, D. 2017. ‘Temporal variation of Seismic coda wave attenuation in the Virunga volcanic region before the eruption of Nyamulagira of 06 November 2011, Democratic Republic of Congo’. D. Delvaux, C. Michellier, O. Dewitte (eds), Geo-Eco-Trop 41/2, special issue : Geohazards in the Great Lakes Region of Central Africa : 205-218. Tervuren : Africa Museum. URL: http://www.geoecotrop.be/ (PR).
Article in a scientific Journal / Article in a Journal
Five periods characterize the temporal variation of the quality factor of seismic coda waves attenuation Q_C^(-1)(Q_0^(-1)) at 9 Hz and lapsed time of 30 seconds, before the Nyamulagira eruption of 6 November 2011 in the Virunga volcanic region of eastern Democratic Republic of Congo. The period I (January – March 2011) was characterized by low attenuation. It grows during period II (April – August 2011) to reach a maximum on the period III (September – October 2011) and decreases during period IV (01 – 06 November 2011). A significant decrease in attenuation characterizes the period V (7 November 2011 – January 2012). An average attenuation growth preceded the magmatic eruption for about 7 months, with a transitional period (III) of maximum attenuation less than 2 months (46 days) before. This period corresponds to the emplacement of the magma in a confined storage area or into a shallow magma chamber and the creation of new fractures/cracks. A drop of attenuation is observed two days before the eruption after a total saturation of the fluid in fractures/cracks (period IV). Periods (I – III and IV – V) correspond respectively to the magmatic intrusion and eruption. The variation of the frequency parameter of Coda wave n indicates a change in the degree and dimension of fracturing over time. The significant differences between periods illustrate the change in volcanic activity in the Virunga region.