Information message about destructive earthquake in Chechnya on October 11, 2008.

     On October 11, 2008 at 09:06 a.m. GMT (13:06 Moscow time) the earthquake with М=5.6 has happened in Chechen Republic, which caused victims and destructions.
     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 6 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 43 stations, accurate processing - with data 60 stations.
     Fig. 1 presents fragments of records from digital stations Botakoyurt (∆ 1.3º), Kislovodsk (∆ 2.7º), Garni (∆ 3.5º), Dombai (∆ 3.5º), Sochi (∆ 4.8º). Fig. 2 presents fragments of records from digital stations Obninsk (∆ 13.4º), Arti (∆ 15.2º), Borovoe (∆ 18.6º), Ala Archa (∆ 20.6º), Kurchatov (∆ 23.1º).

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 09-06-08.0 43.37 46.35  10  60  5.6/165.7/297.5-8 54 IPC GS RAS (Accurate)
2 09-06-09.0 43.46 46.32  10  43  5.6/145.8/107.5-8 54 IPC GS RAS (Preliminary)
3 09-06-09.0 43.47 46.34  15  279  5.9Mw   84 CSEM
4 09-06-10.0 43.29 46.3  10  224  5.9Mw 5.7/196 36 NEIC (Accurate)
5 09-06-08.3 43.59 46.33  1  47  5.9Mw 5.8/16  NEIC (Preliminary)
  • 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
         Epicenter of this earthquake (on fig. 3 depicted with yellow arrow) was located on the territory of Chechen Republic in the border area with Dagestan, 21 km N of Gudermes, 40 km NW of Dylym, 55 km E of Grozny, 61 km SW of Kizliar.

    Figure 3
    Aftershock
         Within the first day after the main shock GS RAS registered 11 aftershocks with magnitudes from 3.6 to 5.4.
    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
    200833282008-10-11 09:22:00.043.4246.2210364.8/ 75.4/ 136.5-7 Eastern Caucasus
    200833302008-10-11 09:44:24.043.446.361010-4.3/ 33.5-4 Eastern Caucasus
    200833312008-10-11 10:28:32.043.546.173311-4.0/ 3-Eastern Caucasus
    200833322008-10-11 10:43:24.043.446.243311-4.1/ 3-Eastern Caucasus
    200833342008-10-11 11:21:27.042.5645.933312-4.2/ 5-Eastern Caucasus
    200833352008-10-11 12:28:19.043.3346.31029-4.7/ 104.5-5 Eastern Caucasus
    200833392008-10-11 21:12:34.043.2346.153311-4.4/ 32-2.5 Eastern Caucasus
    200833402008-10-11 23:51:04.043.3246.193317-4.3/ 8-Eastern Caucasus
    200833462008-10-12 06:39:48.043.3646.26108-3.8/ 12.5-3 Eastern Caucasus
    200833472008-10-12 06:51:06.043.3346.33107-3.6/ 12-2.5 Eastern Caucasus
    200833452008-10-12 09:01:21.043.5346.191017-4.2/ 53.5 Eastern Caucasus
    Macroseismic manifestations
         This earthquake involved 5 territorial regions of Russian Federation (Chechen Republic, Dagestan, Ingush Republic, Osetiya and Stavropol Region), as well as Georgia and Armenia. This earthquake was felt in Grozny, Kizliar, Novolaksk – with intensity 6, in Khasaviyur - with intensity 5, in Kumukh, Dilim - with intensity 4-5, in Piatigorsk, Makhachkala, Gofitskoe, Mozdok, Svetlograd - with intensity 3-4, in Vladikavkaz, Mekhelt, Derbent, Armavir - with intensity 2-3 (fig. 4). The most destructive effects of this earthquake were registered in Kurchaloevsk region and in Gudermes. Partial destructions also were observed in Shalinsk and Gudermes regions and in Grozny and Argun cities. Seven private houses were hit in Avturi settlement of Shalinsk region and also the central regional hospital, in which therapeutic, gynecological and child’s premises were partially destroyed. After this earthquake 13 people were killed and more than 100 injured. Nearly 400 houses cannot be restored. In accordance with ITAR TASS the shocks from this earthquake were felt in Georgian capital Tbilisi - with intensity 3-4, in border areas of RF - with intensity 4-5. In Armenia this earthquake was felt in Vedi of Ararat region with intensity 4.

    Figure 4
    Historical records
         Epicenter of this earthquake belongs to the region of Tersk Ridge of Tersk-Caspian flexure. Seismic tectonic location of this earthquake’s origin is determined by it’s belong to one of the sub latitudinal regional deep ruptures of the Northern Caucasus - Medium rupture of "Caucasian" direction of propagation. Fig. 5 shows location of the main shock with seismo tectonic scheme in the background in accordance with [Bogachkin and others, 1990) together with epicenters of the week earthquakes of this zone in January-August of current year. Seismic activity of 2008 is characterized by rather low level at the peripheral parts of the reported here territory, this activity was registered in the zone of Benoisk-Eldarovsk junction zone, the north-west part in the beginning of the year and south-eastern part in March-April. The most significant earthquake has occurred here on March 31, 2008 at 20:17 with М=4.7, it was located in 40 km from the reported here earthquake. It was felt in Bachi-Yurt with intensity 4, in Gudermes - with intensity 3-4, in Makhachkala with intensity 3-4. Another earthquake with М=3.6 which was located even closer to the reported here event has happened on April 4, 2008. It has happened in highly seismic active region. In the close proximity to epicenter of the earthquake on October 11 (not far than 100 km) there was observed theinfluence of of the strongest earthquakes, which happened in the western part of Tersk-caspian fluxure, to the west and to the south from currently reported earthquake. Fig. 6 depicts the strongest earthquakes located close to the earthquake on October 11 with the seismic tectonic scheme as the background (Bogachkin and others., 1990). Blue lines- sub latitudinal deep ruptures, lilac lines- diagonal joints zones in the foundation, thin rose lines – ruptures, which restrict late Jurassic sub meridian flexure. Chernogorsk earthquake has happened in 1976 with intensity 8-9 in epicenter and М=6.4, since the end of XIX century till the beginning of XXI century more than 20 earthquakes with intensity 6 and more were registered here. The most significant of them are 8 MSK Tersk (Eldarovsk) earthquake of 1912 with М=5.7 and origin in mantle; 7-8 MSK Vedenovsk earthquake of 1933 with М=5.2 and a few 7 MSK earthqukes, which happened in 1785 (Dagestan –I), in 1868, in 1928 (Argunsk), in 1966 (Argunsk-II), in 1969 (Achkhoi-Martanovsk), in 1971 (Starogroznensk), in 1974 (Salataussk). Chernogorsk earthquake of 1976 was accompanied with numerous aftershocks; two earthquakes have happened in 1984 almost in the same epicentral zone with time difference of 9 hours and intensities 6-7 MSK and и М=5.2-5.3, which were accompanied with numerous secondary shocks. After that the most significant earthquakes with less energy level and located at the distance of approximately 100 km to the west and to the east from the earthquake on October 11 have happened on: August 3, 1989 with М=5.0, on January 31, 1999 with М=5.1, on October 12, 2006 with М=4.5 and origin in the upper mantle. The closest to current most significant and strongest earthquakes were registered on March 31 (Gudermess–I), М=4.2, Io=6-7, and on November 9, 1950 – Gudermess–II ), М=5.0, Io=6.

    Figure 5
    Figure 6
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solution of the origin for the earthquake October 11.10.2008 was calculated by IPC GS RAS from the fist signs of P wave arrivals at 63 stations, 51 of these stations registered compression waves (plus signs), 12 registered waves of expansion (minus signs). These stations are located in interval of epicentral distances of Δ=0.4-58º at rather uniform distribution along azimuths. Focal mechanism solution of the origin is presented on figure 7 in stereographic projection at lower half sphere. Fig. 8, 9 present focal mechanism solutions calculated with spatial waves from TMC technique in NEIC USA, USGS and from CMT technique in HRVD USA (Global CMT Catalog). Table 2 presents focal mechanism elements for all solutions. These solutions are close to each other, the type of motion along both planes in accordance with NEIC – "pure" uplift , in accordance with IPC GS RAS and HRVD - uplift with shift components (along NP1- right side, along NP2 – left side). This earthquake has occurred under the action of compression strengths oriented to the north. Both nodal planes in accordance with NEIC and one of them in accordance with IPC GS RAS and HRVD propagate from the north-west to the south-east, the other nodal plane in accordance with IPC GS RAS and HRVD propagates from N-E to S-W. Falling angle of these planes in all solution is rather steep. The value of seismic moment Мо obtained in IPC GS RAS from Р-wave spectra at Talaya station (Δ 38.7º) makes Мо=1.0* 10** 18 n*M, the value of moment magnitude calculated from Kanamori formula makes Mw=6.0. The value of seismic moment Мо of the earthquake 11.10.2008 in accordance with USGS makes Мо=3.2* 10** 17 n*m, the value of moment magnitude Mw=5.6; and in accordance with HRVD Мо=6.6* 10** 17 n*m, Mw=5.8.
    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
    622590349 28792845112754 5153IPC GS RAS
    781951114 01042855790104 3390NEIC
    7326535 17962915011279 4466HARVARD
  • IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences
  • NEIC - National Earthquakes Information Center of US Geological Service
  • HARVARD - Harvard Geophysical Center (USA)

    • Figure 7
    Figure 8

    Figure 9


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