2:45 PM - 3:00 PM
[J05-5-06] Seismicity and Geothermal activities in the Upemba Rift Basin (SE of the DR Congo)
The Upemba Rift Basin (URB) in the Southeastern area of the DR Congo is one of the nascent southwestern branch of the East African Rift System (EARS). Classically, the EARS had been subdivided in two developed branches : eastern and western branch. But, recent studies and observations led to the definition of two additionnal nascent branches, a Southeastern and a Southwestern.
The first develops in the Mozambic rift channel and the second includes the Okavango basin in Botswana, the Luano, Lukusashi, Lwangwa rift valleys in Zambia and the Mweru and Upemba rifts in DR Congo. Among them, the URB is the less knwon and poorly documented. It is oriented NE-SW and fill by the Karoo and recent glacio-fluvio-lacustrine sediments.
Gravity and structural evidence as long as seismicity and geothermal activities confirm the rifting ascent processus. The surface tracing, poorly controlled by gravity due to the reduced number of measurement points, is transverse to a sub-meridian gravity accident between 26 and 27 East meridians.
Last twenty years seismic events recorded are generally of magnitude Mb about 4.2 showing the seismicity axis parallel to the NE-SW trend of the structural look of the recent rift basins. Major earthquakes focal mechanism solutions are consistent with the NW-SE crustal extension.
Numerous thermal springs had been recognized around the URB and the first, now defunct, geothermal power plant in Africa built in 1953 in the Upemba valley. Its geothermal system is still active (recent exploitation indicates hot spring of about 85.0 ~ 87.2 celcius degree, 60 Tons/hour outflow). A recent Natural Source Audio Magnetotelluric profile below the thermal spring indicates the presence of an high resistivity dyke body (up to 10000 ohm-m2 resistivity). This particular area requires a more scientific investigation.
The first develops in the Mozambic rift channel and the second includes the Okavango basin in Botswana, the Luano, Lukusashi, Lwangwa rift valleys in Zambia and the Mweru and Upemba rifts in DR Congo. Among them, the URB is the less knwon and poorly documented. It is oriented NE-SW and fill by the Karoo and recent glacio-fluvio-lacustrine sediments.
Gravity and structural evidence as long as seismicity and geothermal activities confirm the rifting ascent processus. The surface tracing, poorly controlled by gravity due to the reduced number of measurement points, is transverse to a sub-meridian gravity accident between 26 and 27 East meridians.
Last twenty years seismic events recorded are generally of magnitude Mb about 4.2 showing the seismicity axis parallel to the NE-SW trend of the structural look of the recent rift basins. Major earthquakes focal mechanism solutions are consistent with the NW-SE crustal extension.
Numerous thermal springs had been recognized around the URB and the first, now defunct, geothermal power plant in Africa built in 1953 in the Upemba valley. Its geothermal system is still active (recent exploitation indicates hot spring of about 85.0 ~ 87.2 celcius degree, 60 Tons/hour outflow). A recent Natural Source Audio Magnetotelluric profile below the thermal spring indicates the presence of an high resistivity dyke body (up to 10000 ohm-m2 resistivity). This particular area requires a more scientific investigation.