Information message about the bunch of earthquakes in the south of Sakhalin island, september 1, 2001 |
| On September 1, 2001 the bunch of sensitive earthquakes has been registered in the south of Sakhalin island. The strongest of them has happened at 17:08 of Moscow time (13:08 GMT) with magnitude 5.0 and the jar intensity up to 6 MSK. |
| 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 ÷ 4 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 13 stations, accurate processing - with data 29 stations. |
| Figures 1-2 present fragments of records obtained by IPC from digital stations in a close to real time mode. |
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 |
13-08-13.30 |
47 |
142 |
33 |
13 |
4.90/7 | 5.30/6 | 5 | | IPC GS RAS (Preliminary) | | 2 |
13-08-11.1 |
47 |
142 |
10 |
29 |
5.0/13 | 5.4/15 | 5-7 | | IPC GS RAS (Accurate) | | 3 |
13-08-13.3 |
47 |
142 |
|
|
5.2 | | | | IPC GS RAS (Sakhalin center of RAS) | | 4 |
13-08-15.46 |
47 |
142 |
33 |
115 |
| 5.7/70 | | | NEIC (Preliminary) | | 5 |
13-08-11.98 |
47 |
142 |
10 |
129 |
4.8/62 | 5.7/80 | | | NEIC (Accurate) | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Epicenter |
| This earthquake has occurred in the south part of Sakhalin island in the zone of seismic activity, in 45 km to the North-West from South-Sakhalin town. Alert Service has processed 5 shocks from this swarm of the earthquakes in the period between 1 and 2 of September. Information on them is given in table 2.
|
| Aftershock |
| Revival of seismic activity in this region has begun since July 2001. The first weak shock has been registered on July 23, while in the period between 2 and 11 of August AS has registered six shocks with insignificant magnitude, but they were felt in regional settlements Dolinsk, Sosnovka, Bikov, Sinegorsk with intensity up to 5 MSK; in Holmsk up to 3 MSK and in South Sakhalin town up to 2-3 MSK. Between September 1 and 3 seismic station of South Shalin has registered more than 50 underground shocks. Information about most significant of them is published on www-ceme.gsras.ru and given in table 2. Also it can be accessed on the site of South Sakhalin seismic station http://yss.dtn.ru.
|
| 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 |
| 20011227 | 2001-09-01 12:04:47.0 | 47.13 | 143.05 | 33 | 9 | 3.6/ 6 | 3.9/ 5 | 3 | Sakhalin, Russia | | 20011228 | 2001-09-01 12:15:58.0 | 47.23 | 142.82 | 33 | 7 | 4.4/ 2 | 4.3/ 3 | 4-4.5 | Sakhalin, Russia | | 20011230 | 2001-09-01 13:08:11.0 | 47.22 | 142.62 | 10 | 29 | 5.0/ 13 | 5.4/ 15 | 7 | Sakhalin, Russia | | 20011231 | 2001-09-01 20:40:50.0 | 47.08 | 142.7 | 33 | 7 | 3.6/ 5 | 4.1/ 3 | 3 | Sakhalin, Russia | | 20011236 | 2001-09-02 04:39:03.0 | 47.3 | 142.5 | 33 | 1 | 4.0/ 1 | - | 3.5-4 | Sakhalin, Russia | |
| Macroseismic manifestations |
| The earthquake has been felt in towns Holmsk and Dolinsk with intensity 5 MSK, in Nevelsk, Ogonki, Korsakov – 4 MSK, in South Sakhalinsk – 3-4 MSK.
According to the data of South Sakhalinsk seismic station – on September the 1-st since 11pm of Sakhalin local time seismic activity has increased in the Dolinsk region taking the form of another swarm of earthquakes in the area between settlements Sinegorsk, Bikov and Sokol. Within 2 hours seismic station "South Sakhalinsk" registered two dozens of earthquakes, 12 of them have been felt by residents of Dolinsk region, while six of them have been felt by citizens of regional center. Preliminary data of processing showed that maximal intensity in the adjacent settlements did not exceed 6 MSK (Uglezavodsk, Pokrovka, Bikov, Sokol – 6 MSK, South-Sakhalinsk – 3-4 MSK). According to the information from Civil Defense Ministry local office in Sakhalin there were no destructions in the adjacent places.
|
| Historical records |
| Origin zone of September 1, 2001 earthquake belongs to the south zone of extended seismic activity of Sakhalin region. In the last ten years residents of the island witnessed seismic activities in two other zones – in the north of island the strong and catastrophic earthquake has happed in Neftegorsk on May 27, 1995 with М=7.7 and thousands of victims, in the central part of this island more than a year ago (August 5, 2000) the strong Uglegorsk earthquake, has happened with significant destructions.
Southern part of this island was rather calm, at least no earthquakes were known here in the last century with magnitude 5.5 and only in 1916, 1923, 1928, 1938 and 1949 the earthquakes with magnitudes less than 4.8-5.2 (from data of "Specialized Catalogue" (red. N.V. Kondorskaya, V.I. Ulomov)) have been registered. Seismic activity increase in this region has begun since July 2001. The first weak shock has been registered on July 23, while in the period between 2 and 11 of August AS has registered six shocks with insignificant magnitude, but they were felt in regional settlements Dolinsk, Sosnovka, Bikov, Sinegorsk with intensity up to 5 MSK; in Holmsk up to 3 MSK and in South Sakhalin town up to 2-3 MSK.
Historical events of Sakhalin Island from the last century (data of "Specialized Catalogue" and seismic bulletin of CEME GS RAS) and up to now (for July and August the data from operative catalogue of Sakhalin Seismic Party Alert Service have been taken) are shown on the map (fig. 3).
|
Figure 3 |
|
| Focal mechanism and seismic moment of the earthquake |
| Table 3 and figure 4 present solution of focal mechanism obtained in Harvard (USA) from CMT method. The value of seismic moment from data of this center made Mo=8.5 10*23dn*cm, moment magnitude Mw=5.3.
|
| 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 |
| 83 | 7 | 6 | 220 |
4 | 129 | 314 | 39 | 96 | 126 |
51 | 85 | HARVARD | |
| HARVARD - Harvard Geophysical Center (USA) |
Figure 4 |
|
