Information message about the strong earthquake in Tuva Republic on February 26, 2012 |
| The strong earthquake with M=6.8 has occurred in Tuva Republic on February 26, 2012 at 06:17 GMT (10:17 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 11 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 63 stations, accurate processing - with data 72 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Talaya (∆ 4.8º), Ulaanbaatar (∆ 8.1º), Kurchatov (∆ 10.9º), Borovoe (∆ 15.7º), Ala-Archa (∆ 17.2º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 22.3º), Tiksi (∆ 24.8º), Lovozero (∆ 33.1º), Obninsk (∆ 34.6º), Kislovodsk (∆ 35.9º). |
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 |
06-17-17.3 |
51.72 |
95.97 |
10 |
72 |
6.8/31 | 6.7/34 | 9 | 45 | IPC GS RAS (Accurate) | | 2 |
06-17-17.4 |
51.73 |
95.98 |
10 |
63 |
6.8/31 | 6.7/31 | 9 | 49 | IPC GS RAS (Preliminary) | | 3 |
06-17-19.5 |
51.75 |
96.04 |
10 |
772 |
Mw 6.8 | | | 16 | CSEM | | 4 |
06-17-19.8 |
51.73 |
95.92 |
11.7 |
578 |
Mw 6.7 | 6.4/301 | | 18 | NEIC | | 5 |
06-17-20.6 |
51.71 |
95.93 |
10 |
|
6.5 | К 15.7 | | | ASRIPC | | 6 |
06-17-18.3 |
51.9 |
96 |
10 |
|
6.5 | К 16.3 | | | BB SD GS RAS | | 7 |
06-17-16.0 |
51.88 |
95.59 |
10 |
|
6.4 | К 15.6 | 8.5 | | 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 on the territory of Tuva Republic at the depth of 10 km, 38 km N-N-E of Sarig-Sep, 107 km east of Kyzyl, 165 km N-W of Kungurtug and 376 km S-E of Abakan.
|
Figure 3 |
|
| Aftershock |
| GS RAS registered 16 aftershocks with М>4 within one day 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 |
| 20120760 | 2012-02-26 06:52:37.0 | 51.76 | 96.16 | 10 | 20 | - | 5.1/ 8 | 5.5-6 | Southwestern Siberia, Russia | | 20120761 | 2012-02-26 07:49:01.0 | 51.72 | 96.09 | 10 | 10 | - | 4.4/ 4 | 4 | Southwestern Siberia, Russia | | 20120762 | 2012-02-26 08:16:58.0 | 51.73 | 96.12 | 10 | 16 | - | 4.6/ 6 | 4.5 | Southwestern Siberia, Russia | | 20120763 | 2012-02-26 11:07:38.0 | 51.65 | 96.18 | 10 | 32 | - | 5.3/ 18 | 6-6.5 | Southwestern Siberia, Russia | | 20120768 | 2012-02-26 11:50:48.0 | 51.59 | 96.05 | 10 | 15 | - | 4.5/ 7 | 4-4.5 | Southwestern Siberia, Russia | | 20120765 | 2012-02-26 11:59:04.0 | 51.77 | 95.84 | 10 | 34 | - | 5.4/ 17 | 6-6.5 | Southwestern Siberia, Russia | | 20120769 | 2012-02-26 12:50:21.0 | 51.73 | 96.14 | 10 | 19 | - | 4.7/ 10 | 4.5-5 | Southwestern Siberia, Russia | | 20120766 | 2012-02-26 13:06:37.0 | 51.85 | 95.59 | 10 | 23 | - | 5.1/ 13 | 5.5-6 | Southwestern Siberia, Russia | | 20120773 | 2012-02-26 13:17:33.0 | 51.53 | 95.6 | 10 | 15 | - | 4.5/ 3 | 4-4.5 | Southwestern Siberia, Russia | | 20120774 | 2012-02-26 13:44:51.0 | 51.53 | 96.01 | 10 | 16 | - | 4.6/ 8 | 4.5 | Southwestern Siberia, Russia | | 20120775 | 2012-02-26 15:23:27.0 | 51.61 | 96.11 | 10 | 9 | - | 4.3/ 3 | 3.5-4 | Southwestern Siberia, Russia | | 20120776 | 2012-02-26 17:21:39.0 | 51.84 | 96.13 | 10 | 13 | - | 4.2/ 4 | 3.5 | Southwestern Siberia, Russia | | 20120777 | 2012-02-26 18:10:33.0 | 51.75 | 96.07 | 10 | 9 | - | 4.1/ 5 | 3-3.5 | Southwestern Siberia, Russia | | 20120778 | 2012-02-26 19:59:28.0 | 51.61 | 95.96 | 10 | 25 | - | 5.0/ 8 | 5-5.5 | Southwestern Siberia, Russia | | 20120786 | 2012-02-26 23:23:47.0 | 51.4 | 96.39 | 10 | 14 | - | 4.3/ 5 | 3.5-4 | Southwestern Siberia, Russia | | 20120782 | 2012-02-27 02:54:55.0 | 51.65 | 95.87 | 10 | 33 | - | 4.7/ 17 | 4.5-5 | Southwestern Siberia, Russia | |
| Macroseismic manifestations |
| Information Agency RIA-Novosti reported that the Authorities of Tuva Republic announced the regional state of emergency in accordance with this earthquake. Echo of this earthquake was felt in Krasnoyarsk Region, Altai, Khakasia and Tomsk Regions.
GS RAS reported that in accordance with MSK-64 scale this earthquake was felt with the following intensities: in Sarig-Sep 6-7, in Kyzyl 6, in Orlik 4, in Krasnoyarsk and Irkutsk 3-4, in Angarsk, Usolie-Sibirskoye and Sayansk 2-3, in Barnaul 2. |
| Historical records |
| Another earthquake with М=6.8 was registered in the same region 2 months before this earthquake on December 27, 2011 with М=6.7. Epicenter of that earthquake was located 15 km N-W. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism of the earthquake occurred on February 26, 2012 at 6h17m was calculated in the IPC GS RAS with signs of P-wave first arrival at 254 stations, including 241 stations which have recorded compression waves (“plus” sign) and 13 stations with recorded tension waves (“minus” sign). The stations are located in the range of epicentral distances of 1.5º–93º uniformly in azimuth. The fault-plane solutions in stereographic projection on lower hemisphere are shown in Fig.4, their elements are presented in Table 2. Also the fault-plane solutions calculated at the the National Earthquake Information Center of the U.S. Geological Survey (USGS NEIC) with Body-Wave Moment Tensor Solution technique and at the United States Quick CMT Catalog with centroid moment tensor technique (Global CMT Project Moment Tensor Solution) are given in Table.2 and Fig.5, 6.
All solutions are similar. The earthquake has occurred under impact of compressive stress oriented northeast (IPC GS RAS and USGS NEIC solutions) or southwest (Quick CMT solution). Type of movement for both nodal planes - reverse fault with small strike-slip components (IPC GS RAS and Quick CMT) or strike-slip (left-lateral for NP1 plane with Stk=267º or right-lateral for NP2 plane with Stk=165º) with reverse dip-slip components (USGS NEIC). Both nodal planes are rather steeply dipping (DP = 36º-66º) in all solutions, and their strike vary in the range of 20 degrees: Stk = 147º, 165º, 145º for southeast direction and Stk = 290º, 267º, 288º for west and northwest one.
Seismic moment of the earthquake on February 26, 2012 determined in the IPC GS RAS from the P-wave spectra at two stations ("Kislovodsk» with Δ=35.89º and «Obninsk» with Δ=34.64º) is Mo=1.6*10**19 N*m. The average value of moment magnitude Mw calculated by the Kanamori formula is Mw=6.8. According to the USGS NEIC (Body-Wave Moment Tensor Solution), Mo=6.8*10**18 N*m, Mw=6.5; according to the Quick CMT Catalog, Mo=1.04*10**19 N*m, Mw=6.6.
|
| 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 |
| 68 | 159 | 12 | 35 |
18 | 301 | 290 | 60 | 69 | 147 |
36 | 121 | IPC GS RAS | | 36 | 126 | 1 | 36 |
54 | 305 | 267 | 66 | 28 | 165 |
65 | 153 | NEIC | | 70 | 118 | 4 | 218 |
19 | 309 | 288 | 45 | 62 | 145 |
52 | 115 | 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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