Information message about the earthquake at Aleut (Rat) Islands on June 23, 2003 |
| On June 23, 2003 the strong earthquake has happened in Aleut (Rat) Islands . It occured at 16:12 Moscow time (12:12 GMT) with magnitude 7.2 |
| 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 48 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 37 stations, accurate processing - with data 45 stations. |
| Fig. 1 represents fragments of records from digital stations Petropavlovsk-Kamchatsky (delta 11,2 degrees), Magadan (delta 16,7 degrees), College Outpost, Alaska, USA (delta 22,7 degrees), Bilibino (delta 17,4 degrees), South-Sahalinsk (delta 22,5 degrees), Tiksi (delta 29,2 degrees).
Fig. 2 represents fragments of records from digital stations Talaya ( delta 44 degrees), Borovoe (delta 59 degrees), degrees), Arti (delta 61 degrees), Obninsk (delta 69 degrees), Kislovodsk (delta 77 degrees), Garni (delta 80 degrees).
|
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 |
12-12-35.60 |
51 |
176 |
33 |
45 |
7.20/21 | 6.50/20 | 8-8.5 | 83 | IPC GS RAS (accurate) | | 2 |
12-12-35.50 |
51 |
176 |
33 |
37 |
7.3/13 | 6.8/10 | 8.5-9 | 145 | IPC GS RAS (preliminary) | | 3 |
12-12-32.6 |
51 |
176 |
10 |
364 |
7.3 | 5.9-6.5 | | 29 | CSEM | | 4 |
12-12-35.79 |
51 |
176 |
30 |
166 |
6.9/73 | 6.1/97 | | | NEIC (accurate) | | 5 |
12-12-38.41 |
51 |
176 |
33 |
115 |
| 5.9/11 | | | NEIC (preliminary) | |
| 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 |
| The earthquake 23.06.2003 has happened in seismic active region, 85 km to the North-West from Kiska volcano. More detailed info may be found on the site of National Earthqakes Information Center of the US Geological Service http://wwwneic.cr.usgs.gov/neis/bulletin/neic_vjan.html |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions for the earthquake 23.06.2003 have been calculated with TMC method by different centers - National Earthqakes Information Center of the US Geological Service (NEIC), HARVARD (USA), they are presented in table 2 and shown on fig. 3-4.
Solutions obtained in different centers are similar. Motion in origin was under the action of prevailing compression strengths oriented in South-East direction. One nodal plane(NP1) is oriented to the North-East direction steep falling angle(Dp=77 and 75 degr.), the other plane(NP2) slightly sloping(Dp=19 and 25 degr.), but has near to latitudinal direction(HARVARD), or oriented almost along meridian(NEIC).
Seismic moment Мо determined in IPC GS RAS from Р-wave spectra at "Talaya" station (delta=44 degr.), Arti(delta=61 degr.), Obninsk(delta=69 degr.), Kislovodsk(delta=77 degr.) made the value Mo=5.6*10**19 n*m. The value of moment magnitude from these data - Mw=7.1.
The value of seismic moment Mo determined in NEIC made Mo=1.1*10**19 n*m, the value of moment magnitude Mw=6.4.
The value of seismic moment Mo obtained in HRV made Mo=2.6*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 |
| 56 | 346 | 31 | 137 |
14 | 235 | 59 | 77 | 104 | 191 |
19 | 44 | NEIC | | 56 | 307 | 27 | 168 |
19 | 68 | 62 | 75 | 70 | 296 |
25 | 141 | HARVARD | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| HARVARD - Harvard Geophysical Center (USA) |
Figure 3 | 
Figure 4 |
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