Successive earthquakes felt after Nyiragongo eruption

After Nyiragongo Eruption on May 22, 2021, small earthquakes of magnitude up to 5.1 are occurring originating from Rubavu District.  The earthquakes originating mainly from Rubavu sector are felt in different parts of the country, some people in Eastern province claim to have felt them too.

Most of the earthquakes epicenters recorded are located in Cyanzarwe and Rubavu sectors.

Such earthquakes are called “Volcano tectonic earthquakes and are produced by vibrations generated by the movement of magma within the volcano. Pressure beneath the surface of earth increases and the surrounding rock fails, creating small successive earthquakes.” Says RMB’s seismologist Tite Niyitegeka

“Prior to the eruption, no seismic earthquakes (swarms) or other seismic anomalies were recorded. Seismic activities in range of magnitude 2.5 to 4 ML were only observed since the start of the eruption of the volcano and they grew in frequency an hour after eruption with epicenters located in Rubavu District, Cyanzarwe and Rubavu Sector.”

The lava reached and stopped flowing at 1km away from Goma Airport, which is 1km away from the border of Rwanda (Rubavu district).

Nyiragongo is one of the eight volcanoes of Virunga Massif. The seven remaining are:  Nyamuragira, Mikeno, Karisimbi, Bisoke, Sabyinyo, Gahinga and Muhabura.

This range of volcanoes is one of ranges that are lying inside the East African Rift System (EARS).

Only Nyamuragira and Nyiragongo are active. This is proven by a lava lake inside the crater of Nyiragongo and various volcanic activities (earthquake swarms) within the 2 volcanoes.

Nyiragongo past major eruption was in 2002 through its southern flank toward Goma city where the mapped volume of lavas was estimated 22 x 106 m3 and lava flow speed reached 100km/h.

It reopened the 1977 fracture system and killed 250 people and left 120,000 homeless.

After this eruption, about 100 earthquakes (M>3.5) were recorded in the volcano area during the 5 days following the eruption with main effects on Rubavu and Goma and clearly felt as far away as Bukavu and Kigali.

During the past eruption, in 2002, fractures were created in Rubavu District.