[S07-3] Hazard and risk assessment II

[S07-3-06] SEISMIC RISK FOR CITIES AROUND THE LAKE KIVU BASIN, WESTERN BRANCH OF THE EAST-AFRICAN RIFTS SYSTEM

^○Wafula Mifundu¹, Kongbo Tambala² (1.KINSHASA, D.R. CONGO, THE UNIVERISITY OF KINSHASA, KINSHASA, D.R. CONGO, 2.CRSN/ LWIRO, D.S. BUKAVU, D.R. CONGO)

The tectonic conditions of the dome uplift, faulting, volcanism and shallow seismicity around the Lake Kivu (the highest 1462 m) are believed to be the indications of actual rifting and may represent a nascent stage in the development of plate boundary. Since 1997, it was observed in the Lake Kivu Basin the recrudescence of seismic activity. This seismic activity is mostly concentrated in the South-Western part of the Basin where earthquakes are regularly felt. Three large earthquakes associated with foreshocks and long duration aftershocks mostly confined around the epicenter areas were already recorded in the Basin: The October 24th event with magnitude mb (6.1), the February event with magnitude mb (6,0) and the August 7, 2015 event with magnitude mb (5,8). Three events occurred at shallow depth around 10 km. It was observed small Tsunamis during these earthquakes reaching 5 m high and landslides on the shorelines near the epicenters. Many damages are regularly recorded in the villages and towns mostly near the epicenters area. Most of damages are correlated with the secondary faults which move when large earthquake occurred. More than 50 persons are already killed since 2002, by the earthquakes. The maximum intensity observed near the epicenter area is usually more than 8. According to the actual development of seismic activity, more large event is expected. The occurrence of such large earthquake may be catastrophe for the dense cities around the Lake Kivu basin in D.R. Congo and Rwanda side. The situation may be more catastrophe if it occurs inside the lake containing dissolved gas; carbon dioxide (CO2) and methane (CH4) in the deep water, with the possibility of gas explosion. This assertion is supported by the existence of active faults in this lake.
Keywords: Lake Kivu Basin, seismic, risk, faults, catastrophe.