Information message about the strong earthquake in the region of Andreanof Islands, Aleutian Islands, on December 19, 2007 |
| On December 19, 2007 the strong earthquake with M=7 occurred in the region of Andreanof Islands, Aleutian Islands at 09:30 GMT (12:30 am 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 40 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 presents fragments of records obtained from digital stations Bilibino (∆ 18.1º), Seimchan (∆ 19º), Erimo (∆ 27º), Yakutsk (∆ 29º), Tiksi (∆ 30.4º). Fig. 2 presents fragments of records obtained from digital stations Ala Archa (∆ 66.5º), Obninsk (∆ 69.7º), Kislovodsk (∆ 78.3º), Kashpersky Gori (∆ 79.3º), Garni (∆ 81.1º). |
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 |
09-30-28.8 |
51.33 |
-179.56 |
60 |
45 |
7/20 | 6.5/22 | 7-7.5 | 79 | IPC GS RAS (Accurate) | | 2 |
09-30-28.9 |
51.41 |
-179.53 |
60 |
37 |
7/13 | 6.5/14 | 7-7.5 | 79 | IPC GS RAS (Preliminary) | | 3 |
09-30-29.5 |
51.39 |
-179.43 |
60 |
370 |
7.2Mw | | | 53 | CSEM | | 4 |
09-30-31.0 |
51.49 |
-179.47 |
56 |
130 |
7.2Mw | | | 54 | 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 the picture downloaded from the US Geological Service, NEIC , which presents epicenter of this earthquake, which was located in the Bering Sea (at the depth of 60 km) near Amatignak Island being part of Andreanof Islands.
|
Figure 3 |
|
| Aftershock |
| This earthquake has been accompanied with aftershocks, the strongest of them with с М>4.7 have been registered by Geophysical Survey of RAS and they are presented below for the date of December 20. |
| 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 |
| 20074397 | 2007-12-19 09:35:20.0 | 51.63 | -179.16 | 33 | 11 | - | 5.8/ 4 | 5.5 | Andreanof Islands, Aleutian Is. | | 20074398 | 2007-12-19 09:44:22.0 | 51.34 | -179.13 | 60 | 27 | - | 5.8/ 11 | 4.5-5 | Andreanof Islands, Aleutian Is. | | 20074399 | 2007-12-19 09:46:52.0 | 50.02 | -177.14 | 10 | 20 | - | 5.8/ 15 | 7-7.5 | Andreanof Islands, Aleutian Is. | | 20074400 | 2007-12-19 10:01:03.0 | 51.1 | -179.12 | 60 | 21 | - | 5.3/ 10 | 3-3.5 | Andreanof Islands, Aleutian Is. | | 20074401 | 2007-12-19 10:05:30.0 | 50.94 | -179.54 | 10 | 17 | - | 5.1/ 9 | 5.5-6 | Andreanof Islands, Aleutian Is. | | 20074402 | 2007-12-19 10:24:34.0 | 51.36 | -179.46 | 50 | 23 | - | 5.5/ 15 | 4-4.5 | Andreanof Islands, Aleutian Is. | | 20074403 | 2007-12-19 10:56:37.0 | 51.33 | -179.59 | 50 | 16 | - | 5.0/ 5 | 3 | Andreanof Islands, Aleutian Is. | | 20074404 | 2007-12-19 11:15:25.0 | 51.07 | -178.74 | 70 | 16 | - | 4.8/ 4 | 2 | Andreanof Islands, Aleutian Is. | | 20074406 | 2007-12-19 11:46:42.0 | 50.89 | -179.14 | 60 | 19 | - | 4.9/ 8 | 2-2.5 | Andreanof Islands, Aleutian Is. | | 20074407 | 2007-12-19 12:30:50.0 | 51.13 | -179.25 | 50 | 30 | - | 5.5/ 15 | 4-4.5 | Andreanof Islands, Aleutian Is. | | 20074408 | 2007-12-19 13:04:18.0 | 50.86 | -179.14 | 50 | 22 | - | 4.8/ 10 | 2.5 | Andreanof Islands, Aleutian Is. | | 20074409 | 2007-12-19 14:04:39.0 | 50.96 | -179.28 | 50 | 18 | - | 4.9/ 9 | 2.5-3 | Andreanof Islands, Aleutian Is. | | 20074410 | 2007-12-19 14:51:35.0 | 51.18 | -179.56 | 50 | 21 | - | 5.4/ 7 | 3.5-4 | Andreanof Islands, Aleutian Is. | | 20074412 | 2007-12-19 18:16:57.0 | 51.07 | -179.15 | 50 | 13 | - | 4.8/ 7 | 2.5 | Andreanof Islands, Aleutian Is. | | 20074413 | 2007-12-19 20:51:22.0 | 51.21 | -179.42 | 50 | 16 | - | 4.7/ 5 | 2-2.5 | Andreanof Islands, Aleutian Is. | | 20074416 | 2007-12-20 02:18:19.0 | 51.08 | -178.8 | 33 | 19 | - | 5.2/ 9 | 4-4.5 | Andreanof Islands, Aleutian Is. | | 20074419 | 2007-12-20 03:51:45.0 | 51.55 | -179.46 | 33 | 15 | - | 4.9/ 6 | 3-3.5 | Andreanof Islands, Aleutian Is. | |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions of the earthquake 19.12.2007 0=09-30 М=7.0 calculated with method of tensor moment centroid in the National Information Center of the US Geological Service (NEIC) and in the Harvard Center, USA (HARVARD) are presented in table 2 and shown on fig. 4,5. These solutions are almost the same. The earthquake has occurred under prevailing action of compression forces oriented to the south–south-east. The flat nodal plane (NP2) has close to latitudinal direction of propagation, the motion along it is presented by the thrust components of right sided drift.
Steeply falling plane (NP1) propagates to the north-east direction, the type of motion along it – uplift with left side drift components.
The value of seismic moment in accordance with NEIC makes Мо =6.7* 10** 19 n*m, the value of moment magnitude - Mw = 7.2, and in accordance with HARVARD – Мо=6.34* 10** 19 n*m, Mw = 7.1.
|
| 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 |
| 66 | 327 | 23 | 162 |
5 | 70 | 68 | 68 | 84 | 264 |
23 | 105 | NEIC | | 64 | 317 | 24 | 162 |
10 | 67 | 64 | 70 | 80 | 271 |
23 | 116 | HARVARD | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| HARVARD - Harvard Geophysical Center (USA) |
Figure 4 | 
Figure 5 |
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