Significant building damage was reported after a shallow M5.3 earthquake (RMB) hit Rubavu, Rwanda at 09:03 UTC (11:03 LT) on May 25, 2021. The USGS is reporting it as M4.7 at a depth of 10 km (6.2 miles).
This is the strongest of numerous earthquakes recorded in the region after the eruption of a nearby Nyiragongo volcano on May 22, including M3.3, M3.7, M4.0, M4.4, and M4.7.
Tremors are shaking the region every 10 to 15 minutes.
According to the Rwanda Mines, Petroleum and Gas Board (RMB; Rwanda Seismic Monitor) the earthquakes are located mainly in the Rubavu and Cyanzarwe sectors and are felt in different parts of the country.
"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," said RMB seismologist Tite Niyitegeka.
"Prior to the eruption, no seismic earthquakes (swarms) or other seismic anomalies were recorded. Seismic activities in the 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."
In addition to earthquakes, cracks are now appearing around the volcano, including in Goma and Rwanda's Rubavu District. The same phenomenon was occurring after previous eruptions of Nyiragongo in 1977 and 2002.
As of May 25, the death toll rose to 32 and is expected to continue growing. At least 9 of them died in traffic accidents while trying to flee and 7 from inhaling toxic gas while walking across a wide expanse of the cooling lava.