SOME SISMIC ASPECTS PRIOR THE NOVEMBER 06, 2011 NYAMULAGIRA ERUPTION, DEMOCRATIC REPUBLIC OF CONGO

Résumé fourni par la source

The Nyamulagira volcano enters in eruption approximately each 2 years and the last eruption of November 06, 2011 was started 22 months after that of January 02, 2010. The aim of this work is the characterization of some aspects of seismicity prior the Nyamulagira eruption on 2011by temporal analysis of the hypocenters (epicenters and depths), earthquake number and spectral frequency. A temporal evolution showed that the seismicity rate, the hypocenters, the corner frequency and energies release vary and give a comprehension of the behavior of the volcanic activity. 10 months before the eruption, earthquakes were deep (10 - 30 km) and scattered with weak corner frequencies (< 2.6 Hz) in the field of Nyamulagira. That confirms a partial melt or deep magmatic intrusion with weak displacement. The magmatic migration starts between April and October 2011 with shallow earthquakes (0 - 5 km) and high corner frequency and high energy. This period prepares a pathway of magma to the surface. The frequency and energy were then higher in the last swarms of 04 and 05 November 2011, 2 days prior the eruption. This last seismicity denote at the same time a magmatic intrusion, a fracturing of the weakness zones and an extrusion of the lava at the surface. A deep investigation of these parameters on several eruptive cycles would facilitate the knowledge of the magmatic dynamics of Nyamulagira volcano and also the predictive approach of its eruptions.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.