Inforamation message about the strong earthquake near the western coast of Sakhalin island, Russia, August 02, 2007

     The strong earthquake with M-6.2 has happened in Tatar channel near the South-Western coast of Sakhalin Island, Russia, on August 02, 2007 at 02:37GMT (06:37 Moscow time, 13:37 local time). It caused victims and destructions.
     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 37 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 25 stations, accurate processing - with data 43 stations.
     Fig. 1 presents fragments of records obtained from digital stations Yuzhno-Sakhalinsk (∆ 0.7º), Petropavlovsk (∆ 12.5º), Magadan (∆ 13.9º), Yakutsk (∆ 16.8º), Seimchan (∆ 17.2º). Fig. 2 presents fragments of records obtained from digital stations Bilibino (∆ 24.8º), Talaya (∆ 25.2º), Tiksi (∆ 25.7º), Kurchatov (∆ 40.7º), Arti (∆ 49.5º).

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 02-37-39.6 46.68 141.77  10  43  6.2/175.4/187-8108 IPC GS RAS (Accurate)
2 02-37-40.0 46.75 141.72  10  25  6.1/135.4/147-8217 IPC GS RAS (Preliminary)
3 02-37-44.4 47.26 141.76  10    5.8Mw 5.3/107  NEIC (Preliminary)
4 02-37-43.5 47.26 141.75  5  138  6.2Mw 5.3/122 122 NEIC (Accurate)
  • IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences
  • NEIC - National Earthquakes Information Center of US Geological Service
    • Epicenter
         Epicenter of this earthquake (depicted with blue triangle on fig.3) was located in Tatar channel, approximately in 7 km to the West from Nevelsk town at 80 km to the South-West from Yuzhno-Sakhalinsk town. Settlements are shown with red and turquoise circles on fig.3.

    Figure 3
    Aftershock
         Fig.4. presents magnitude dispersion of aftershocks. GS RAS has registered 19 aftershocks with M>=4 by August 6, 2007 (four days and five hours after the main shock).

    Figure 4
    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
    200728112007-08-02 02:59:47.046.55141.811025-4.8/ 144.5-5 Sakhalin, Russia
    200728132007-08-02 03:45:42.046.96141.761024-4.8/ 124.5-5 Sakhalin, Russia
    200728162007-08-02 04:14:03.047.01141.61018-4.6/ 104.5 Sakhalin, Russia
    200728092007-08-02 05:01:44.046.52141.671026-5.3/ 126-6.5 Sakhalin, Russia
    200728102007-08-02 05:22:16.046.66141.7720345.7/ 195.8/ 136.5-7 Sakhalin, Russia
    200728172007-08-02 05:34:55.046.66141.641014-4.6/ 94.5 Sakhalin, Russia
    200728192007-08-02 05:39:13.046.92141.691012-4.6/ 64.5 Sakhalin, Russia
    200728142007-08-02 06:04:40.046.51141.811016-4.9/ 105-5.5 Sakhalin, Russia
    200728152007-08-02 08:06:26.046.68141.781027-5.6/ 116-7Sakhalin, Russia
    200728242007-08-02 10:03:36.047.07141.851011-4.5/ 54-4.5 Sakhalin, Russia
    200728212007-08-02 10:11:04.046.43141.891011-4.8/ 64.5-5 Sakhalin, Russia
    200728202007-08-02 10:37:29.046.58141.781029-5.6/ 116-7Sakhalin, Russia
    200728232007-08-02 11:33:40.046.5141.781011-4.8/ 64.5-5 Sakhalin, Russia
    200728322007-08-02 14:29:01.046.54141.71013-4.4/ 44 Sakhalin, Russia
    200728362007-08-03 00:42:22.047.15141.81012-4.2/ 43.5 Sakhalin, Russia
    200728432007-08-04 04:33:25.046.78141.772083.6/ 14.3/ 14Sakhalin, Russia
    200728462007-08-04 07:37:13.046.92141.773393.7/ 14.0/ 23-3.5 Sakhalin, Russia
    200728522007-08-04 22:21:52.046.72141.7610234.3/ 64.8/ 75Sakhalin, Russia
    200728692007-08-06 07:38:37.046.8142.17107-4.3/ 53.5-4 Sakhalin, Russia
    Macroseismic manifestations
         In accordance with data from seismic station "Yuzhno-Sakhalinsk" this earthquake was felt in Nevelsk town – with intensity 6 MSK, in Holmsk town – with intensity 5 MSK, in Yuzhno-Sakhalinsk town – with intensity 4 MSK. The earthquake has originated weak tsunami with 20 cm wave. One aftershock which happened at 05:22 GMT with М=5.7 has been felt in Yuzhno-Sakhalinsk with intensity 4 MSK, in Ogon’ki – with intensity 3 MSK. Another aftershock, which happened at 08:06 GMT with М=5.6 has been felt in Yuzhno-Sakhalinsk, Nevelsk, Holmsk with intensity 4 MSK. Aftershock, which happened at 10:37 GMT with М=5.6 has been felt in Gornozavodsk, Korsakov, Krillione with intensity 3 MSK. From preliminary data there are numerous destructions and two persons killed in Nevelsk town. As witnesses say, the saw cracks in the walls of the houses and broken foundations of the buildings, but no one living building was totally destroyed. Concrete fencing along the highway has fallen. One 23-years old girl has been killed, when she was in the cultural center during the earthquake, cap of the building has fallen on her in course of evacuation. Numerous injured persons are registered. People left their homes in fear of additional shocks and tsunami. As EMERCOM of Russia reports, the special rescue team has moved to the region of the earthquake
    Historical records
         Fig.5 presents seismic conditions and history of Sakhalin island since 1895 up now in accordance with data from "New catalogue of the strong earthquakes on the territory of USSR " and Operative Seismological bulletin of GS RAS. The reported earthquake has occurred in the southern part of Sakhalin Island (fig.5). Fig. 6 presents the scheme of seismic structures and regional zoning of Sakhalin Island (in accordance with Dr. Soloviev S.L.., 1968). From this scheme one can see that within the area of Sakhalin mountainous structure it is possible to distinguish the number of active deep junctions. Structural elements from this scheme are located in the area of this earthquake (fig.6-1-9). Epicenter of this earthquake is situated on the rupture zone (fig.5-1) near the structures (fig.6-5,4) and (fig.6-2,3). The system of longitudinal ruptures (fig.6-1) spreads along the island close to the western coast in the Middle and Southern parts of Sakhalin island. It segregates growing Western-Sakhalin anticlinorium from synclinorium of Tatar channel. Modern activity of this system of ruptures probably was the reason of Uglegorsk earthquake (1924, 1949, (1956, М-5.0), Lesogorsk earthquake (1928, М=5.5) Alexandrovsk earthquake (1935, М=5.5) and some other minor events. Investigation of the junction located at the bottom of Tatar channel is rather difficult task. The system of deep longitudinal ruptures, which constrain West-Sakhalin anticlinorium from the east (fig.6-2), was the subject of field investigations. This junction along with nearby located ruptures is the source of numerous earthquakes, such as Onorsk earthquakes (1909, 1912, 1959), Sinegorsk earthquakes (1923-1924), Ado-Timovsk earthquake (1949, М=5.2), Perevalsk earthquake (1949, М-5.2). It is supposed the existence of longitudinal deep rupture (fig.6-3) at the eastern side of central Sakhalin depressions. The origin place of Vladimir earthquake, which happened on August 9, 1960 with =4.7, is located in the contact zone between Susunaisk ridge and Susunaisk depression. Significant tectonic break, which is not longitudinal but latitudinal to the main structures of the island (fig.6-4), is observed along the line Aniva-Holmsk and further within the margins of th shelf till the island’s slope. From the south-west this supposed deep junction is joining the zone of newest and modern relative depressions, especially intensive near the coasts, this is in the area of Aniva settlement and to the north from Holmsk (fig.6-5). This zone is visible distinctively at the map with epicenters (fig. 5), this may confirm the existence of deep junction and flexures managed by this junction located near the bottom of Krilion peninsula, as well as rather intensive activity of modern motions in this zone. These structures determined Anivsk earthquake (1951, М=5.5). Taranaisk earthquake (1963, М=4.3) and the number of other minor events in the area of Holmsk town, including some shocks at the shelf of Tatar channel. The strongest Moneronsk earthquake, which happened on September 5, 1971 (46.47ºN, 141.72ºE М=7.5) («New Catalogue, 1977») also belongs to this area. Underwater ridges exist at the south-east near Moneron Island with adjusent deep water structures of Japanese See (fig.6-6,7,8,9).

    Figure 5
    Figure 6
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism solution of the earthquake 02.08.2007 has been calculated in NEIC, USA with TMC method. It is presented in table 2 and on fig. 7. The motion in origin has occurred under the action of prevailing compression forces, oriented in latitudinal direction. Both nodal planes have almost the same longitudinal direction of propagation. One of them NP1 lays flat, the type of motion along it is thrust; the other plane NP2 steeply falls , the type of motion along it - uplift. Averaged value of seismic moment Мо determined by IPC GS RAS from Р-wave spectra obtained at two seismic stations "Obninsk" (delta 61 degrees) and "Arti" (delta 50 degrees) is equal to 3.0* 10** 18 n*m. The value of moment magnitude from this data is equal to Mw = 6.3. The value of seismic moment Мо in accordance with NEIC is equal to 2.2* 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
    682772296 018618523896 6791NEIC
  • NEIC - National Earthquakes Information Center of US Geological Service

    • Figure 7


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