Seismic activity prior to the May 8, 2004 eruption of volcano Nyamuragira, Western Rift Valley of Africa

The spatial–temporal variation in the seismicity in the Nyamuragira area related to different stages of magmatic activity was examined for the period August 18, 2002, to May 7, 2004, prior to the Nyamuragira eruption of May 8, 2004. It is found that swam-type seismicity composed mainly of long-period earthquakes foreran by 2–4 months the eruption of Nyamuragira and was enhanced by tectonic seismicity related to rifting. Ten months before eruption, a steady increase in seismicity at a constant rate from a deep magma feeder was observed. In the last stage (1 or 2 months) before the eruption, the hypocenters of long-period earthquakes became shallower.