Information message about sensitive earthquake near the eastern coast of Kamchatka on February 20, 2011 |
| The sensitive earthquake with M=6.2 20 has occurred near the eastern coast of Kamchatka on February 2011 at 21:43 GMT (21 February 2011 at 00:43 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 13 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 55 stations, accurate processing - with data 61 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Petropavlovsk (∆ 3.5º), Bilibino (∆ 12.5º), Kurilsk (∆ 14º), Yakutsk (∆ 15.8º), Erimo (∆ 18.6º). Fig. 2 presents fragments of records obtained from digital stations Borovoe (∆ 49.9º), Arti (∆ 52.4º), Obninsk (∆ 61º), Kislovodsk (∆ 68.4º), Garni (∆ 70.9º). |
Figure 1
| 
Figure 2
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|
| 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 |
21-43-20.6 |
55.75 |
162.47 |
33 |
61 |
6.2/29 | 6.2/32 | 6.5-7 | 74 | IPC GS RAS (Accurate) | | 2 |
21-43-20.8 |
55.77 |
162.47 |
33 |
55 |
6.2/28 | 6.2/27 | 6.5-7 | 74 | IPC GS RAS (Preliminary) | | 3 |
21-43-21.2 |
55.97 |
162.22 |
10 |
423 |
| 6 | | 45 | CSEM | | 4 |
21-43-20.7 |
55.92 |
162.14 |
9.8 |
535 |
5.9/461 | 6.1/426 | | 22 | NEIC | | 5 |
21-43-22.8 |
55.75 |
162.48 |
30 |
|
К 13.8 | | | | KRIPC | |
| 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 |
| KRIPC - Regional Informational Processing Center of Kamchatka |
| Epicenter |
| Fig.3 presents with red star epicenter of this earthquake, it's origin was located near the eastern coast of Kamchatka at the depth of 33 km, 55 km to the south of Ust-Kamchatsk and 390 N-E of Petropavlovsk-Kamchatskiy. |
Figure 3 |
|
| Macroseismic manifestations |
| This earthquake was felt in Ust-Kamchatsk and Klyuchi with intensities 3-4 MSK, in Petropavlovsk-Kamchatskiy with intensities 2-3 MSK. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of this earthquake which occurred on February 20, 2011 at 21:43 GMT was calculated in IPC GS RAS with the signs of initial arrivals of P-waves at 153 stations, including 43 stations which registered the waves of compression (plus signs), and 110 stations which registered the waves of expansion (minus signs). These stations are located in the interval of epicenter distances of 7º-95º between them with rather uniform distribution along the azimuths. Focal mechanism of the origin is presented in figure 4 in stereographic projection at lower hemisphere, elements of this mechanism are presented in table 2. Table 2 and figures 5, 6 also present focal mechanism solution, which was obtained with CMT method in NEIC, USGS and Global CMT Catalog, USA.
All solutions are almost identical. This earthquake has occurred under the action of expansion and compression forces oriented nearly along latitudinal direction of propagation. Both nodal planes have nearly along meridian direction of propagation, one of them is steeply falling, almost vertically (DP=72º–87º), the other is flat (DP=3º-24º). The type of motion along both planes – fault (with small component of left side shift along the flat plane).
Seismic moment of this earthquake which occurred on February 20, 2011 was calculated by IPC GS RS with Р-wave spectra obtained at four stations: «Talaya» (∆ 34.12º), «Arti» (∆ 52.38º), «Obninsk» (∆ 61.01º), «Kislovodsk» (∆ 68.42º), it makes Мо=1.6* 10** 18 n*m. Averaged value of moment magnitude Mw was calculated with Kanamori formula and makes Mw=6.1.
The value of seismic moment Мо of this earthquake which occurred on February 20, 2011 in accordance with USGS makes 2.0* 10** 18 n*m, the value of moment magnitude makes Mw = 6.1. The value of seismic moment Мо in accordance with Global CMT Catalog makes 2.15* 10** 18 n*m, the value of moment magnitude makes Mw = 6.2.
|
| 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 |
| 25 | 277 | 60 | 61 |
15 | 180 | 37 | 24 | -50 | 175 |
71 | -106 | IPC GS RAS | | 52 | 264 | 38 | 83 |
0 | 173 | 1 | 7 | -83 | 174 |
83 | -90 | NEIC | | 42 | 282 | 48 | 102 |
0 | 192 | 22 | 3 | -80 | 192 |
87 | -90 | 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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