Information message about the strong earthquake in Tuva Republic on December 27, 2011. | | The strong earthquake with M=6.7 has occurred on December 27, 2011 at 15:21 GMT (19:21 Moscow time) in Tuva Republic. | | 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 14 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). | | Preliminary processing has been done with data from 65 stations, accurate processing - with data 72 stations. | | Fig. 1 presents fragments of records obtained from digital stations Talaya (∆ 4.9º), Dzhasator (∆ 5.7º), Ulaanbaatar (∆ 8.3º), Kurchatov (∆ 10.9º), Borovoe (∆ 15.6º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 22.1º), Tiksi (∆ 24.7º), Obninsk (∆ 34.5º), Kislovodsk (∆ 35.8º), Bilibino (∆ 36.5º). |
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 |
15-21-55.3 |
51.83 |
95.83 |
10 |
72 |
6.7/33 | 6.5/32 | 7-8 | 49 | IPC GS RAS (Accurate) | | 2 |
15-21-55.4 |
51.83 |
95.85 |
10 |
65 |
6.7/31 | 6.5/31 | 7-8 | 49 | IPC GS RAS (Preliminary) | | 3 |
15-21-57.1 |
51.84 |
95.85 |
10 |
258 |
| 6.5 | | 39 | CSEM | | 4 |
15-21-56.5 |
51.86 |
95.83 |
6.9 |
227 |
Mw 6.6 | 6.2/133 | | 36 | NEIC | | 5 |
15-21-59.0 |
51.92 |
95.7 |
10 |
|
6.5 | | | | ASRIPC | | 6 |
15-21-55.0 |
51.79 |
95.89 |
10 |
|
6.3 | | | | BB SD GS RAS | | 7 |
15-21-55.0 |
51.74 |
95.82 |
10 |
|
6.1 | | | | KNIIGiMS | | | 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 | | ASRIPC - Regional Informational Processing Center of Altai-Saiyany Experimental-Methodical Seismological Expedition Geophysical Survey Siberian Branch Russian Academy of Sciences | | BB SD GS RAS - Baikal Branch of Siberian Division of GS RAS | | KNIIGiMS - KNIIGiMS | | Epicenter | | Fig.3 presents with red star epicenter of this earthquake which origin was located in Tuva Republic at the depth of 10 km, in 38 km N-E of Sarig-Sep, in 80 km S-W of Toora-Khem, in 101 km E of Kizil, in 177 km N-W of Kungurtug and in 365 km S-E of Abakan. | 
Figure 3 |
| | Aftershock | | GS RAS registered 9 aftershocks with M>4 in 14 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 |
| 20115197 | 2011-12-27 15:53:06.0 | 51.79 | 95.97 | 10 | 26 | - | 4.6/ 8 | 4.5 | Southwestern Siberia, Russia | | 20115198 | 2011-12-27 16:12:32.0 | 51.94 | 95.76 | 10 | 22 | - | 4.3/ 8 | 3.5-4 | Southwestern Siberia, Russia | | 20115199 | 2011-12-27 20:19:11.0 | 51.73 | 96.12 | 15 | 21 | - | 4.9/ 12 | 4.5-5 | Southwestern Siberia, Russia | | 20115206 | 2011-12-27 20:29:41.0 | 51.53 | 96.33 | 10 | 15 | - | 4.1/ 6 | 3-3.5 | Southwestern Siberia, Russia | | 20115203 | 2011-12-27 23:43:51.0 | 52.09 | 95.63 | 15 | 11 | - | 4.4/ 6 | 3-3.5 | Southwestern Siberia, Russia | | 20115204 | 2011-12-28 00:40:32.0 | 52.08 | 95.65 | 10 | 21 | - | 5.0/ 9 | 5-5.5 | Southwestern Siberia, Russia | | 20115208 | 2011-12-28 04:11:44.0 | 51.78 | 96.17 | 10 | 10 | - | 4.3/ 5 | 3.5-4 | Southwestern Siberia, Russia | | 20115207 | 2011-12-28 04:23:39.0 | 51.82 | 95.69 | 10 | 35 | - | 5.0/ 12 | 5-5.5 | Southwestern Siberia, Russia | | 20115209 | 2011-12-28 04:45:53.0 | 51.72 | 96.03 | 10 | 15 | - | 4.4/ 3 | 4 | Southwestern Siberia, Russia | | | Macroseismic manifestations | | In accordance with RIA-Novosti authorities of Tuva Republic announced the state of emergency of regional level for the whole territory of republic after this earthquake. It was also felt in Krasnodar Region, Altai Region, Hakasia and Tomsk Regions.
In accordance with GS RAS this earthquake was felt in Sarig-Sep with intensity 6-7 MSK, in Kizil with intensity 6 MSK, in Orlik with intensity 3-4 MSK, in Ust-kamenogorsk, Novokuznetsk and Krasnoyarsk with intensity 3 MSK, in Irkutsk and Angarsk with intensity 2-3 MSK, in Barnaul and Novosibirsk with intensity 2 MSK. | | Historical records | | This earthquake has occurred on December 27, 2011 in seismic active region and in accordance with the map of general seismic regioning OCP-97-A this region belongs to 8-MSK zone of intensities [Dr. V.Ulomov, Dr. L.Shumilina, 1999]. Historically it is known as the area of strong earthquakes, most significant of them include the following earthquakes:
Earthquake on May 27, 1991 with M=4.9 – on the territory of Mongolia which was felt in some remote settlements of Tuva Republic with intensities 3-4 MSK.
Busingolsk earthquake on December 27, 1991 with M=6.5 – this is one of the strongest events for the whole instrumental period of observations, it occurred in eastern part of Busingol Region near Mongolian border. It was felt on significant territory including Tuva Republic, some part of Irkutsk Region, Krasnoyarsk Region and Mongolia. This earthquake was accompanied with powerful series of aftershocks. [See «The earthquakes of USSR in 1991», Moscow, 1997].
Aginsk earthquake of October 27, 2000 – it occurred at the riverhead of Kann River, approximately 200 km S-E of Krasnoyarsk, it was felt at the whole southern part of the region with intensities from 2 up to 6-7 MSK [See «The earthquakes of Northern Eurasia in 2000», Obninsk, 2006]. The earthquake of August 16, 2008 with M=5.4 – at the border between Russia and Mongolia, it was felt on the territory of Irkutsk Region with intensities 5-6 MSK (Irkutsk 3-4 MSK, Orlik 5-6 MSK) [Alert Service of GS RAS, Obninsk, 2008], .
The previous strong earthquake has occurred in this region of August 4, 2009 with M=5.4 in 50 km W-N-W of Kungurtuga and it was felt in Tuva Republic with intensities 2 - 4 MSK.
| | Focal mechanism and seismic moment of the earthquake | | Fault plane solution of the earthquake which occurred on December 27, 2011 at 15:21 (GMT) was calculated in IPC GS RAS with signs of P-wave first arrivals at 133 stations, including 65 of them which registered compression waves (“plus” signs) and 68 stations which registered tension waves (“minus” signs). These stations are located in the interval of epicentral distances of 4º-92º, they are distributed non-uniformly by azimuth – mainly in quadrants 1, 2 and 4. Focal mechanism in stereographical projection on the lower hemisphere is presented at figure 4, it’s elements are given in table 2. Table 2 and figures 5, 6 also contain focal mechanism solutions calculated with CMT technique in NEIC USGS and in Global CMT Catalog, USA. All solutions are almost identical. The earthquake occurred under the action of compressional and tensional stresses of similar value. Tensional stress is directed northwest (Quick CMT) or southeast (IPC GS RAS, NEIC USGS), and compressional stress is oriented to the southwest.
Nodal plane NP1 has sub-latitudinal strike and steep dipping (DP = 67º - 88º), nodal plane NP2 also dips steeply (DP = 79º-87º), but has near-longitudinal strike.
Type of movement for both planes is strike-slip (left-lateral for NP1 and right-lateral for NP2).
Seismic moment of this earthquake which occurred on December 27, 2011 was calculated in IPC GS RAS with Р-wave spectra obtained at two stations: «Kislovodsk» (∆ 35.80º), «Obninsk» (∆ 34.52º), it makes Мо=7.0*10**18 N*m. Averaged value of moment magnitude Mw was calculated with Kanamori formula and makes Mw=6.6.
In accordance with USGS Мо=8.7*10**18 N*m, Mw=6.6. In accordance with Global CMT Catalog Мо=1.31*10*19 N*m, Mw=6.7. | | 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 |
| 5 | 115 | 10 | 206 |
78 | 360 | 250 | 79 | -4 | 341 |
86 | -169 | IPC GS RAS | | 1 | 121 | 4 | 211 |
86 | 23 | 256 | 87 | -2 | 347 |
88 | -177 | NEIC | | 18 | 303 | 14 | 208 |
67 | 82 | 76 | 88 | 23 | 345 |
67 | 177 | 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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