Information message about sensitive earthquake in Black Sea December 23, 2012 |
| The sensitive earthquake with M=5.6 has occurred in the Black Sea, offshore Georgia, on December 23, 2012 at 13:31 GMT (17:31 Moscow time). |
| 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 9 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 45 stations, accurate processing - with data 56 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Neitrino (∆ 1.5º), Lazarevskoe (∆ 1.8º), Kislovodsk (∆ 1.9º), Tuapse (∆ 2.1º), Vozrozhdenie (∆ 2.9º). Fig. 2 presents fragments of records obtained from digital stations Kiev (∆ 11.5º), Obninsk (∆ 12.9º), Arti (∆ 17.9º), Vasula (∆ 18.3º), Borovoe (∆ 22.2º). |
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 |
13-31-38.4 |
42.51 |
40.97 |
10 |
56 |
5.6/19 | 5.8/20 | 7.5-8 | 45 | IPC GS RAS (Accurate) | | 2 |
13-31-38.6 |
42.54 |
40.95 |
10 |
45 |
5.6/17 | 5.8/17 | 7.5-8 | 51 | IPC GS RAS (Preliminary) | | 3 |
13-31-40.8 |
42.581 |
40.98 |
10 |
760 |
Mw 5.5 | | | 12 | CSEM | | 4 |
13-31-39.9 |
42.417 |
41.064 |
10 |
325 |
5.6/299 | 5.5/251 | | 25 | NEIC | | 5 |
13-31-37.5 |
42.44 |
41.02 |
5 |
59 |
ML 5.5 | | | | KOERI | | 6 |
13-31-38.2 |
42.458 |
41.108 |
1 |
8 |
ML 6 | | | | UNSSPG | |
| 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 |
| KOERI - Kandilli Observatory and Earthquake Research Institute, Turkey |
| UNSSPG - United National Survey for Seismic Protection , Georgia |
| Epicenter |
| Fig. 3 presents with red star epicenter of this earthquake, it's origin was located in the Black Sea, offshore Georgia, at the depth of 10 km, 56 km S of Sukhumi, 111 km N-N-W of Batumi and 160 km S-E of Sochi. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 9 aftershocks with M>3.7 within 10 hours after the main shock. |
| 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 |
| 20124667 | 2012-12-23 13:48:46.0 | 42.6 | 41.05 | 10 | 11 | - | 3.8/ 1 | 2.5-3 | Western Caucasus | | 20124668 | 2012-12-23 13:50:42.0 | 42.53 | 40.99 | 10 | 14 | - | 3.8/ 2 | 2.5-3 | Black Sea | | 20124670 | 2012-12-23 13:54:04.0 | 42.6 | 40.99 | 10 | 14 | - | 3.7/ 1 | 2-2.5 | Black Sea | | 20124671 | 2012-12-23 14:18:46.0 | 42.65 | 40.91 | 10 | 12 | - | 3.9/ 3 | 2.5-3 | Black Sea | | 20124672 | 2012-12-23 15:09:17.0 | 42.51 | 41.02 | 10 | 15 | - | 3.7/ 2 | 2-2.5 | Western Caucasus | | 20124673 | 2012-12-23 15:18:37.0 | 42.49 | 41.02 | 10 | 24 | - | 4.0/ 5 | 3 | Western Caucasus | | 20124674 | 2012-12-23 18:22:03.0 | 42.68 | 40.99 | 10 | 10 | - | 3.8/ 2 | 2.5-3 | Black Sea | | 20124675 | 2012-12-23 19:33:01.0 | 42.59 | 41.15 | 10 | 18 | - | 4.0/ 4 | 3 | Western Caucasus | | 20124677 | 2012-12-23 22:05:15.0 | 42.48 | 41.01 | 10 | 22 | - | 3.9/ 3 | 2.5-3 | Western Caucasus | |
| Macroseismic manifestations |
| In accordance with GS RAS this earthquake was felt: in Sochi, Adler, Khosta and Dagomys with intensities 5-6 MSK, in Cherkessk, Karachaevsk, Zelenchuk with intensity 3 MSK.
In accordance with NEIC and CSEM this earthquake in Georgia was felt in Tbilisi, Batumi with intensity 5, in Gori, Ozurgeti with intensity 4. |
| Historical records |
| Historical earthquakes with M≤5.5 are known for the area within a radius of 50-70 km from the epicenter of this earthquake (fig. 4). In accordance with data from «New catalogue» (Dr. Kondorskaya, Dr. Shebalin, 1977) three most significant of them are: 1) the earthquake of the year 50 with M=5.5 which destroyed Dioskuria town and caused land slides and maybe tsunami 2) the earthquake of the year 400 with М=5.5 (nearly in the same origin area) which seriously destroyed Sebastopolis town (Sukhumi Bay) – it damaged and declined fortress walls 3) Tsaishsk earthquake of 1615 with M=4.9.
Besides that it is known Achigvarsk earthquake of July 5, 1958 with М=4.6. Another significant earthquakes were regisred in this area on 27.08.1904, 19.01.1935, 20.10.1953 with М=4.2-4.7, they all happened at the shelf part of Black Sea.
|
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of this earthquake was calculated at the IPC GS RAS with signs of initial arrivals of P waves at 85-stations, including 36 stations which registered compression waves (plus signs) and 49 stations which registered extension waves (minus signs). The stations are located in the range of epicentral distances of 0.8º-98º uniformly by azimuths. Focal mechanism solution in stereographic projection at the lower hemisphere is presented at figure 5, elements of the mechanism are presented in table 2. Table 2 and figures 6-7 also present focal mechanism solutions calculated with method of body waves for the moment tensor method at the National Earthquake Information Center of U.S. Geological Survey, USGS NEIC, and the method of centroid moment tensor in the Global CMT Catalog, USA.
All solutions obtained at IPC GS RAS, USGS NEIC and Quick CMT are identical.
This earthquake has occurred under the action of close in value tensile and compressive stresses oriented North and East respectively in case of IPC GS RAS and USGS solutions and West and South in case of Global CMT solution. Both nodal planes are steeply dipping(DP=74-88º). One of the nodal planes has the north-east - south-west orientation, the other - the north-west - south-east one. Type of motion is represented by shifts in the focus on both nodal planes for NP1 - supplied right to NP2 - left hand. Type of motion is a strike-slip on both nodal planes. Right-lateral strike-slip has occured on NP1 plane and left-lateral one - on NP2 plane.
Seismic moment of this earthquake obtained at the IPC GS RAS with spectra of S-wave at «Krasnaya Poliana» station (∆ 1.26º) makes Мо=8.0*10**17 N*m. Seismic moment Мо=3.4*10**17 N*m, moment magnitude Mw=5.6 in accordance with USGS, and Мо=6.14*10**17 N*m, Mw=5.8 in accordance with Global CMT Catalog.
|
| 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 |
| 10 | 352 | 13 | 85 |
74 | 225 | 128 | 74 | -2 | 219 |
88 | -164 | IPC GS RAS | | 12 | 344 | 1 | 75 |
78 | 171 | 29 | 83 | 171 | 120 |
81 | 7 | NEIC | | 9 | 168 | 11 | 259 |
76 | 40 | 34 | 89 | -166 | 303 |
76 | -2 | Quick CMT | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
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