Information message about the earthquake on March 6, 2005 to the North from the North Lanf island |
| The strong earthquake with magnitude 6.0 has been registered in the Arctic basin to the North from Northern Land on March 6, 2005 at 05:21 (GMT). Epicenter of this event was located in Northern Ocean, 1570 km to the North from Tiksi settlement. |
| 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 1 ÷ 45 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Fig. 1 presents fragments of records obtained from digital stations Tiksi (delta 14,3 degrees), Lovozero (delta 20,5 degrees), Yakutsk (delta 23,9 degrees), Magadan (delta 27,7 degrees), Obninsk (delta 33 degrees). Fig. 2 presents fragments of records obtained from digital stations Talaya (delta 33,5 degrees), Petropavlovsk-Kamchatsky (delta 34,9 degrees), South-Sakhalinsk (delta 39,7 degrees), Ala-Archa (delta 43 degrees), Kislovodsk (delta 43,6 degrees). |
Figure 1
| 
Figure 2
|
|
| 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 |
05-21-41.20 |
84.97 |
98.73 |
10 |
38 |
6.00/21 | 6.10/20 | 8.5 | 86 | IPC GS RAS (Accurate) | | 2 |
05-21-44.60 |
84.94 |
98.94 |
33 |
29 |
5.9/12 | 6.1/12 | 6.5 | 86 | IPC GS RAS (Preliminary) | | 3 |
05-21-41.20 |
84.99 |
99.73 |
10 |
387 |
| 6.3 | | 34 | CSEM | | 4 |
05-21-43.73 |
84.94 |
99.14 |
10 |
187 |
| 6.1/125 | | | NEIC (Preliminary) | | 5 |
05-21-43.70 |
84.94 |
98.85 |
10 |
201 |
6.1/118 | 6.1/125 | | 35 | NEIC (Accurate) | | 6 |
05-21-51.20 |
84.84 |
95.66 |
30 |
46 |
| | | 308 | ORFEUS | |
| 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 |
| ORFEUS - Observatories and Research Facilities for EUropean Seismology |
| Aftershock |
| In the period since March 6 till Marh 10, 2005 eight events have happened in the area of Northern Land, the main strike has been registered on March 6 at 05:21 with magnitude Мs=6.0, previous shock – on March6 at 05:01 with mb=5.5 and 6 aftershocks with magnitudes mb from 4.5 up to 5.3. |
| 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 |
| 20050758 | 2005-03-06 05:01:16.0 | 84.84 | 98.13 | 33 | 23 | - | 5.5/ 10 | 4.5-5 | North of Severnaya Zemlya | | 20050794 | 2005-03-06 07:08:56.0 | 84.96 | 97.88 | 33 | 10 | - | 4.6/ 6 | 2.5-3 | North of Severnaya Zemlya | | 20050761 | 2005-03-06 07:12:13.0 | 84.88 | 98.55 | 33 | 17 | 4.3/ 7 | 4.9/ 8 | 4-4.5 | North of Severnaya Zemlya | | 20050762 | 2005-03-06 08:24:48.0 | 84.95 | 99.06 | 33 | 17 | 4.4/ 6 | 5.1/ 8 | 4-4.5 | North of Severnaya Zemlya | | 20050766 | 2005-03-07 03:44:30.0 | 81.43 | 120.5 | 33 | 23 | 4.6/ 9 | 5.3/ 9 | 4.5 | East of Severnaya Zemlya, Russia | | 20050795 | 2005-03-08 17:30:46.0 | 84.74 | 92.41 | 10 | 10 | - | 4.5/ 6 | 4-4.5 | North of Severnaya Zemlya | | 20050792 | 2005-03-10 00:28:24.0 | 85.22 | 91.85 | 10 | 21 | 4.7/ 11 | 5.2/ 11 | 6.5 | North of Severnaya Zemlya | |
| Historical records |
| Figure 3 presents the map of epicenters for the earthquakes registered in the Arctic Region in accordance with Obninsk seismological bulletin for the period 1955-2004. The main feature of this region is the existence of linear seismo active zone (Middle Arctic belt), which runs via deep water part of Arctic basin up to the shelf in Laptev Sea and being part of global seismic belt of middle oceanic ridges, which traces divergent margins of litosphere plates (Avetisov G.P., 1994). In Arctic Region This zone is located close to the underwater cam of Gakkel ridge (Treshnikov A.F., Balakshin A.A. and others. 1967), which itself is the longitudional axis of Eurasian sub basin of Arctic Ocean, it segregates Eurasian and North American plates.
It is necessary to note that in the origin place of this earthquake no other events of the same level of magnitudes (6 and more) have been registered in last 30 years – since October 14 and 18, 1973, which had magnitudes MPSP =6.3 and the earthquake on February 26, 1975 with MPSP =6.2 (in accordance with Obninsk seismological bulletin). From fig. 3 one can see that most significant earthquakes have been registered in South-East of Middle Arctic belt in water area of Laptev sea near Novosibirsk Islands. The earthquakes on April 10, 1909 and on August 25, 1964 with Ms=6.8-7.0 have happened in the same region.
|
Figure 3 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of the earthquake 06.03.2005 has been obtained in IPC GS RAS from the first signs of P-wave arrivals at 129 stations. Waves of compression have been detected at 58 of these stations and they are marked with "+" sign, waves of expansion have been detected at 71 stations (marked with "-"). Table 2 presents elements of focal mechanism from IPC GS RAS data, as well as data calculated with TMC method in NEIC (USA) and in Harvard (USA). Figures 4-6 present the focal mechanisms and graphical presentation in stereographical projection. Solutions obtained in different centers with various methods are close. The motion in origin occurred under expansion strengths oriented to the South-West. The type of motion along both planes - fault. In all solutions one of the nodal planes has North-Western-South-East spread direction and rather steep fall. In accordance with IPC and NEIC data the other nodal plane has latitudinal direction with shift component available in motion.
The value of seismic moment Мо from IPC data makes 3.6* 10** 18 n*m, the value of moment magnitude - Mw = 6.3. From NEIC data-Mo = 2.3* 10** 18 n*m, the value of moment magnitude - Mw = 6.2. The value of seismic moment Мо from Harvard data makes 2.26* 10** 18 n*m, the value of moment magnitude - 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 |
| 23 | 24 | 53 | 147 |
28 | 281 | 272 | 73 | -119 | 155 |
34 | -32 | IPC GS RAS | | 1 | 220 | 57 | 129 |
33 | 310 | 281 | 53 | -133 | 158 |
54 | -48 | NEIC | | 1 | 219 | 88 | 103 |
2 | 309 | 307 | 44 | -93 | 131 |
46 | -87 | HARVARD | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
| HARVARD - Harvard Geophysical Center (USA) |
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