Information message about the strong earthquakes in Northwestern Iran on August 11, 2012 |
| Two strong earthquakes with M=6.5 and M=6.4 has occurred in Northwestern Iran on August 11, 2012 at 12:23 and 12:34 GMT (16:23 and 16:34 Moscow time) respectively. |
| 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 18 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Location of the first earthquake has been done with data from 62 stations, location of the second earthquake - from 51. |
| Fig. 1 presents fragments of records obtained from digital stations Garni (∆ 2.3º), Nalchik (∆ 5.6º), Neitrino (∆ 5.7º), Kislovodsk (∆ 6.4º), Isparta (∆ 12.9º). Fig. 2 presents fragments of records obtained from digital stations Obninsk (∆ 18.1º), Borovoe (∆ 21.7º), Kurchatov (∆ 25.5º), Talaya (∆ 41.2º), Ulaanbaatar (∆ 43.8º). |
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: |
| Note: [1]- данные по первому землетрясению [2]- данные по второму землетрясению |
| 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 |
12-34-34.6 |
38.36 |
46.84 |
10 |
51 |
6.4/23 | 6.2/25 | 9-9.5 | 183 | IPC GS RAS ([2]) | | 2 |
12-23-17.0 |
38.46 |
46.91 |
10 |
62 |
6.5/28 | 6.1/22 | 9-9.5 | 145 | IPC GS RAS ([1]) | | 3 |
12-23-18.1 |
38.41 |
46.81 |
10 |
915 |
Mw 6.4 | | | 20 | CSEM ([1]) | | 4 |
12-34-36.1 |
38.48 |
46.75 |
10 |
886 |
Mw 6.3 | | | 20 | CSEM ([2]) | | 5 |
12-23-17.9 |
38.32 |
46.89 |
9.9 |
448 |
6.7/440 | 6.2/385 | | 36 | NEIC ([1]) | | 6 |
12-34-35.3 |
38.32 |
46.76 |
9.8 |
509 |
Mw 6.3 | 6.3/213 | | 22 | NEIC ([2]) | | 7 |
12-23-15.0 |
38.49 |
46.87 |
10 |
14 |
ML 6.2 | | | | IGUT ([1]) | | 8 |
12-34-34.0 |
38.45 |
46.73 |
10 |
9 |
ML 6.0 | | | | IGUT ([2]) | |
| 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 |
| IGUT - Institute of Geophysics, University of Tehran |
| Epicenter |
| Fig. 3 presents with red star epicenter of the first earthquake which was located in East Azerbaijan Province of Iran at the depth of 10 km, 69 km N-E of Tabriz, 283 km S-E of of Yerevan, the Armenian capital, 325 km S-W of Baku, the Azerbaijan capital. Yellow star presents epicenter of the second earthquake which was located in East Azerbaijan Province of Iran at the depth of 10 km, 12 km S-W of the first shock, 57 km N-E of Tabriz, 287 km S-E of of Yerevan, the Armenian capital, 336 km S-W of Baku, the Azerbaijan capital. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 14 aftershocks with M≥4.3 within 2 days 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 |
| 20123079 | 2012-08-11 12:49:17.0 | 38.4 | 46.97 | 10 | 23 | - | 4.9/ 11 | 5-5.5 | Armenia-Azerbaijan-Iran bord reg | | 20123080 | 2012-08-11 13:05:54.0 | 38.45 | 46.94 | 10 | 16 | - | 4.5/ 9 | 4-4.5 | Armenia-Azerbaijan-Iran bord reg | | 20123081 | 2012-08-11 13:14:06.0 | 38.62 | 46.82 | 10 | 27 | - | 4.8/ 12 | 4.5-5 | Armenia-Azerbaijan-Iran bord reg | | 20123082 | 2012-08-11 14:25:16.0 | 38.4 | 46.87 | 10 | 25 | - | 4.5/ 10 | 4-4.5 | Armenia-Azerbaijan-Iran bord reg | | 20123083 | 2012-08-11 15:21:14.0 | 38.47 | 46.92 | 10 | 37 | - | 4.7/ 24 | 4.5-5 | Armenia-Azerbaijan-Iran bord reg | | 20123084 | 2012-08-11 15:43:19.0 | 38.61 | 46.89 | 10 | 40 | - | 4.9/ 20 | 5-5.5 | Armenia-Azerbaijan-Iran bord reg | | 20123085 | 2012-08-11 16:21:54.0 | 38.26 | 46.77 | 10 | 14 | - | 4.5/ 7 | 4-4.5 | Armenia-Azerbaijan-Iran bord reg | | 20123087 | 2012-08-11 17:58:34.0 | 38.2 | 46.67 | 10 | 17 | - | 4.5/ 7 | 4-4.5 | Armenia-Azerbaijan-Iran bord reg | | 20123088 | 2012-08-11 19:52:47.0 | 38.67 | 47.05 | 10 | 18 | - | 4.7/ 11 | 4.5-5 | Northwestern Iran | | 20123090 | 2012-08-11 22:24:02.0 | 38.38 | 46.71 | 10 | 49 | - | 5.1/ 27 | 5.5-6 | Armenia-Azerbaijan-Iran bord reg | | 20123092 | 2012-08-12 04:25:22.0 | 38.28 | 46.91 | 10 | 19 | - | 4.4/ 7 | 4 | Armenia-Azerbaijan-Iran bord reg | | 20123094 | 2012-08-12 06:40:46.0 | 38.62 | 46.83 | 10 | 14 | - | 4.5/ 7 | 4-4.5 | Armenia-Azerbaijan-Iran bord reg | | 20123099 | 2012-08-13 01:56:10.0 | 38.31 | 46.62 | 10 | 14 | - | 4.8/ 7 | 4.5-5 | Armenia-Azerbaijan-Iran bord reg | | 20123102 | 2012-08-13 08:16:50.0 | 38.2 | 47.03 | 10 | 10 | - | 4.3/ 7 | 3.5-4 | Northwestern Iran | |
| Macroseismic manifestations |
| In accordance with ITAR-TASS brunt of the disaster was in the city of Ahar, Varazkan, Harith. The number of victims reached 300 persons, injuring more than two thousand.
|
Figure 4 |
|
| Historical records |
| Iran is located in a zone of high seismic activity. In the last century the victims of the 20 most powerful earthquakes were more than 170,000 Iranians. December 26, 2003 in the Southeast of Iran as a result of a magnitude 6.6 quake completely destroyed the ancient city of Bam in the southeast of the country. Killing more than 30,000 people. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism of the earthquake on August 11, 2012 was calculated with Centroid Moment Solution method in USGS NEIC and with CMT method in Quick CMT Catalog, USA. These solutions in stereographic projection at the lower hemisphere are presented in figures 5, 6, elements of mechanism are presented in table 2.
Both USGS NEIC and Quick CMT solutions are rather identical.
In accordance with USGS solution, this earthquake occurred under the action of close in value compression and extension stress oriented north-west for compression stress and north-east for extension stress. NP1 nodal plane is steeply dipping (DP=88º), its strike is longitudinal (Stk=357º). NP2 plane is more flat (DP=57º) and has latitudinal strike (Stk=89º). Type of motion along NP1 plane is left-lateral strike-slip with normal fault components or right-lateral strike-slip along NP2 plane.
In accordance with Quick CMT solution, the earthquake also occurred under the action of close in value compression and extension forces, but compression stress has south-east orientation, at similar for both solutions north-east extension stress. Both nodal planes are steeply dipping. NP1 plane has N-E strike (Stk=173º) with dipping angle DP=74º, NP2 plane has latitudinal strike (Stk=82º) and dips more steeply (DP=89º). Type of motion along NP1 plane is left-lateral strike-slip, or right-lateral strike-slip along NP2 plane.
Seismic moment of the earthquake in accordance with USGS NEIC makes Мо=5.8*10**18 N*m, Mw=6.4, in accordance with Quick CMT – Мо=6.28*10**18 N*m, Mw=6.5.
|
| 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 |
| 21 | 48 | 24 | 308 |
57 | 175 | 357 | 88 | -33 | 89 |
57 | -178 | NEIC | | 12 | 36 | 11 | 129 |
74 | 259 | 173 | 74 | 1 | 82 |
89 | 164 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
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