Information message about the strong earthquake in Africa near the Lake Tanganyika on December 5, 2005

     On December 5, 2005 the strong earthquake has happened in Africa at 12:19 GMT (15:19 Moscow time) with magnitude М=6.9. Epicenter of this earthquake was located near the Lake Tanganyika – at the border between Congo and Tanzania. The earthquake was felt in six countries, including Democratic Republic of Congo and Tanzania. Victims and destructions are available.
     Parameters of the earthquake have been determined in the Alert Service (AS) of Information Processing Center (IPC) of Geophysical Survey of RAS in Obninsk with station data obtained from digital and analog seismic stations of Russia, countries of CIS and from abroad. Alert message on this earthquake has been delivered in 48 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 26 stations, accurate processing - with data 39 stations.
     Fig. 1 presents fragments of records obtained from digital stations: Kislovodsk (51.3 degrees), Obninsk (61.3 degrees), Ala-Archa (63.3 degrees), Vasula (64.5 degrees), Arti (66.7 degrees), Konberg (67.6 degrees). Fig. 2 presents fragments of records obtained from digital stations: Borovoe (68.2 degrees), Sanae (68.5 degrees), Kurchatov (70.5 degrees), Lovozero (74 degrees), Ulan-Bator (86.2 degrees), Hailar (94.6 degrees).

Figure 1
 

Figure 2
 
     IPC GS RAS also has obtained information with parameters of this event from some seismological centers, these data are given in table 1:
Table 1
NN Time in origin h-min-s (GMT) Lat degr. Lon degr. Depth km N s/st Ms/ N mb/ N I0 calc GAP Center
1 12-19-52.30 -6.18 29.8  10  39  6.90/106.50/129.5-10156 IPC GS RAS (Accurate)
2 12-19-54.5 -5.9 30.03  10  26  6.9/86.4/69.5-10290 IPC GS RAS (Preliminary)
3 12-19-53.4 -6.15 29.69  10  383  6.9   41 CSEM
4 12-19-55.47 -6.21 29.6  10  107  6.9/26.4/38 40 NEIC
  • IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences
  • CSEM - European - Mediterranean seismological center
  • NEIC - National Earthquakes Information Center of US Geological Service
    • Epicenter
         From tectonic point of view this earthquake has happened on December 5, 2005 in continental rift zone near the Tanganyika (mark 5 on figure 3, from V.E.Hain -"Tectonics of continents and oceans", 2001). From NEIC data no such earthquakes have happened here in this region neither in last nor in current centuries. Strong earthquakes happened at 200-300 kilometers to the west and to the south-east from the place of the reported earthquake (fig.4).

    Figure 3
    Figure 4
    Aftershock
         The main shock was accompanied with 2 weak aftershocks on December 5 (at 13:02 and 15:42 GMT) with magnitude 4. On December 6 more strong aftershock has been registered by GS RAS.
    N Date   &   Time (GMT)
    yy-mm-dd hh:mm:sec    		 Lat
    degr.    		 Lon
    degr.    		 Depth
    km    		 N
    station    		 Ms/ N mb/ N Io
    calc.    		 Region
    200531902005-12-06 05:53:07.0-5.9929.4710144.7/ 65.7/ 66.5 Lake Tanganyika region
    Macroseismic manifestations
         In accordance with Associated Press information (fig. 5) “dozens of houses have fallen and a few children have been buried under the debris of their houses” in Kalemie city at the east of Democratic Republic of Congo. At least two men died in hospital after injuries. Besides that the death of one kid has been registered in Kalemie, where two houses and church have fallen down. Three men were injured in that moment. Camps with refugees are located in this area, many houses are broken. Ground vibrations have been felt at the distance of 1000 kilometers from epicenter in the capital of Kenya. Hundreds of people have been evacuated from high buildings in the center of Nairobi. Underground shocks have been registered even at the Kenyan coast of Indian Ocean.

    Figure 5
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solutions obtained from data of National Earthquakes Information Center of Geophysical Service (NEIC USA) and Harvard Center (HARVARD USA) are shown on fig. 6 - 7 in stereographical projection (lower hemisphere, areas with waves of compression in dark color) and in table 2. These solutions are close to each other. The motion in origin place of the earthquake on December 5, 2005 has happened under the action of expansion strengths oriented in latitudinal direction. Both nodal planes have almost identical directions of propagation (nearly along meridian) with steep falling angles - (DP=40-56 degrees). Type of motion along both planes – trap drown. The value of seismic moment Мо in accordance with NEIC makes 1.2* 10** 19 n*m, the value of moment magnitude - Mw = 6.7. The value of seismic moment Мо in accordance with Harvard makes 1.8* 10** 19 n*m, the value of moment magnitude - Mw = 6.8. The value of seismic moment Мо obtained by IPC GS RAS from Р-wave spectra at 2 stations OBN and ARU makes 2.6* 10** 19 n*m, the value of moment magnitude - Mw = 6.9.
    Table 2
    Axes of main strengths Nodal planes Center
    T P N NP1 NP2
    Pl Azm Pl Azm Pl Azm Stk Dp Slip Stk Dp Slip
    26785319 515715244-97342 47-83NEIC
    88569332 1917815340-12111 56-66HARVARD
  • NEIC - National Earthquakes Information Center of US Geological Service
  • HARVARD - Harvard Geophysical Center (USA)

    • Figure 6
    Figure 7


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