Information message about the strong earthquake in the region of Fox Islands, Aleutian Islands, on June 24, 2011. |
| The strong earthquake with M=7.3 has occurred on June 24, 2011 at 03:09 GMT (07:09 Moscow time) in the region of Fox Islands, Aleutian Islands. |
| 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 15 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 35 stations, accurate processing - with data 61 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Petropavlovsk (∆ 18º), Bilibino (∆ 19.2º), Seimchan (∆ 21.8º), Kurilsk (∆ 27.3º), Yakutsk (∆ 29.1º). Fig. 2 presents fragments of records obtained from digital stations Lovozero (∆ 58.8º), Borovoe (∆ 63.1º), Obninsk (∆ 70.7º), Kislovodsk (∆ 79.9º), Garni (∆ 83º).
|
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 |
03-09-37.7 |
52.03 |
-171.74 |
50 |
61 |
7.3/31 | 7.1/28 | 8 | 46 | IPC GS RAS (Accurate) | | 2 |
03-09-32.6 |
52.04 |
-171.63 |
5 |
35 |
| 6.9/23 | 11-11.5 | 85 | IPC GS RAS (Preliminary) | | 3 |
03-09-40.1 |
52.11 |
-171.83 |
60 |
800 |
Mw 7.3 | | | 24 | CSEM | | 4 |
03-09-40.5 |
52.01 |
-171.86 |
62.6 |
784 |
Mw 7.2 | 6.9/516 | | 29 | 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 presents with red star epicenter of this earthquake which was located in the area of Fox Islands, Aleutian Islands, at the depth of 50 km., in 50 km. S-W off the nearest island. |
Figure 3 |
|
| Aftershock |
| GS RAS registered one aftershock with M=5.2 in 1 hour 11 minutes 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 |
| 20112964 | 2011-06-24 04:20:44.0 | 51.72 | -171.54 | 40 | 29 | - | 5.2/ 13 | 3.5-4 | Fox Islands, Aleutian Islands | |
| Macroseismic manifestations |
| Fig. 4 was downloaded from NEIC USA site, it presents the map of intensities obtained from phone calls to 11 respondents living in 5 places. |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution for the origin of the earthquake which occurred on June 24, 2011 at 05:46 GMT was calculated with moment of centroid technique in NEIC USA, USGS and with CMT technique in Global CMT Catalog, USA. Focal mechanism of the origin in stereographical projection at the lower hemisphere is presented in figures 5,6; elements of this solution are presented in table 2. All solutions are almost identical. The earthquake has occurred under both expansion and compression forces oriented along meridian direction of propagation. Nodal plane of N-E direction of propagation lays flat with right drift type of motion and uplift components along it, while the type of motion for the plane of latitudinal direction of propagation is the fault with left side drift components.
Seismic moment of this earthquake which occurred on June 24, 2011 was calculated in IPC GS RAS with spectra of Р-waves obtained at three stations: «Arti» (∆ 64.24º), "Obninsk" (∆ 70.67º), «Kislovodsk» (∆ 79.87º), it makes Mo=1.9* 10** 20 n*m. Average value of Mw was calculated with Kanamori formula and makes Mw=7.5.
Seismic moment of this earthquake which occurred on June 24, 2011 in accordance with USGS makes Mo=1.1*10**20 n*m and average value of moment magnitude makes Mw=7.3; in accordance with Global CMT – Mo=9.72*10**19 n*m, Mw=7.3.
|
| 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 |
| 42 | 344 | 48 | 177 |
6 | 80 | 16 | 7 | -154 | 260 |
87 | -84 | NEIC | | 41 | 346 | 48 | 180 |
7 | 82 | 19 | 8 | -153 | 263 |
86 | -83 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
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