Information message about the strong earthquake in central part of Kurils Ridge on April 7, 2009 |
| The strong earthquake with M=7 has occurred on April 7, 2009 at 04:23 a.m. GMT (08:23 Moscow time) in central part of Kurils Region. |
| 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 26 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 72 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Erimo (∆ 7.3º), Petropavlovsk (∆ 8.1º), Matsushiro (∆ 13.8º), Seimchan (∆ 16.9º), Bilibino (∆ 23.4º), Talaya (∆ 31.6º). Fig. 2 presents fragments of records obtained from digital stations Kurchatov (∆ 46.9º), Borovoe (∆ 50.5º), Ala Archa (∆ 53.2º), Arti (∆ 54.8º), Obninsk (∆ 65.3º), Kislovodsk (∆ 70.5º). |
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 |
04-23-33.3 |
46.06 |
151.62 |
50 |
72 |
7/19 | 6.4/26 | 7.5 | 49 | IPC GS RAS (Accurate) | | 2 |
04-23-33.4 |
46.08 |
151.62 |
50 |
56 |
7/18 | 6.4/25 | 7.5 | 49 | IPC GS RAS (Preliminary) | | 3 |
04-23-32.6 |
46.11 |
151.59 |
40 |
313 |
7 Mw | | | 49 | CSEM | | 4 |
04-23-34.5 |
46.14 |
151.42 |
39 |
186 |
7 Mw | 6.5/173 | | 50 | NEIC | |
| 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 |
| Epicenter |
| Fig.3 depicts with yellow star epicenter of this earthquake, which was located in central part of Kurils Ridge in Pacific Ocean at the depth of 50 km, in 72 km E-N-E of Cherny Bratia Island, in 307 km E-S-E of Kurilsk town, in 610 km N-W of Severo-Kurilsk town. |
Figure 3 |
|
| Aftershock |
| GS RAS has registered: 1 foreshock with М=5.1 (3 before the main shock) and 1 aftershock with М=4.7 (1 hour 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 |
| 20091181 | 2009-04-07 01:38:58.0 | 45.94 | 151.23 | 70 | 31 | - | 5.1/ 13 | 2.5-3 | Kuril Islands | | 20091183 | 2009-04-07 05:29:45.0 | 46.21 | 151.76 | 50 | 15 | - | 4.7/ 4 | 2-2.5 | Kuril Islands | |
| Macroseismic manifestations |
| This earthquake was felt in Kurilsk town with intensity 3-4 MSK, in Severo-Kurilsk and Yuzhno-Kurilsk with intensity 2 MSK.
|
| Historical records |
| Epicenter of the reported here earthquake was located in origin zone of two strongest earthquakes, which occurred in Kuril Islands on November 15, 2006 and on January 13, 2007 with М=8.2. Another two earthquakes have occurred in that area on March 3, 2008 with М=6.8 and on January 15, 2009 with М=7.2. Fig. 4 presents the strongest earthquakes of this region for 2006-2009 in accordance with GS RAS data. |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanisl solutions for the origin of this earthquake, which happened on April 7, 2009 at 04:23 a.m. (GMT), were obtained with TMC technique in NEIC USA and USGS, they are presented in table 2 and shown on fig. 3.
The earthquke has ocurred under the action of compression forces oriented N–E. Both nodal planes had N-E direction of propagation. One plane steeply falls (falling angle of this plane DP=68º), the other plane lays flat (DP=22º). The type of motion along steeply falling plane – «pure» uplift, and along the flat plane – the thrust with left side components of drift).
The value of seismic moment Мо of this earthquake in accordance with USGS makes 2.9* 10** 19 n*m, the value of moment magnitude Mw = 6.9.
|
| 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 |
| 67 | 315 | 22 | 129 |
2 | 219 | 214 | 22 | 84 | 40 |
67 | 92 | NEIC | |
| NEIC - National Earthquakes Information Center of US Geological Service |
Figure 5 |
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