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Information message about the earthquake on August 5, 2000 on Sakhalin island

On August 5, 2000 at 01:13 Moscow time (August 4 at 21:13 GMT) has occurred strong (M=7.1) earthquake on Sakhalin island with calculating intensity in the epicenter VIII-IX MSK. Earthquake has occurred in underpopulated region of island and was felt up to VI MSK in inhabit points.

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 60 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).

Improved processing has been done with data from 19 stations, in addition to listed above 11 digital stations it was used information from five analog stations of Russia (Northern Kurilsk, Irkutsk, Mahachkala, Piatigorsk, Anapa) and from three stations of CIS : Belorussia (Minsk), Kazahstan (Alma-Ata), Uzbekistan (Tashkent).

Preliminary summary processing of this earthquake has been done with data from eleven digital stations, nine of which are located in Russia (Yuzhno-Sakhalinsk, Petropavlovsk-Kamchatsky, Tiksi, Jakutsk, Magadan, Arti, Talaya, Obninsk, Kislovodsk), one in Mongolia (Ulan-Bator), one in the USA, in Alaska (College Outpost). Waveforms from these stations are coming to GS RAS (Obninsk) in near real time mode, where their station processing is done with special programs, which calculate the main parameters of the origin.In figures 1-2 one can find records from digital stations, which were obtained in IPC in near 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	21-13-05.80	48	142	33	19	7.10/12	6.00/1	8-8.5		IPC GS RAS (improved)
2	21-13-05.8	48	142	33	11	7.0/9		8-8.5		IPC GS RAS (initial)
3	21-13-02.1	48	142			6.3				IPC GS RAS (Sakhalin experimental methodical expedition GS RAS)
4	21-13-09.3	49	142	33	72		6.0-6.5			CSEM
5	21-13-03.0	48	142	10	135	7.0				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

The location of improved hypocenter determined by IPC GS RAS is shown on figure 3 in red.

Figure 3

Aftershock

This earthquake was accompanied with aftershocks.

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
20001023	2000-08-04 21:13:05.0	48.85	142.42	33	19	7.1/ 12	6.0/ 1	8-8.5	Sakhalin, Russia
20001024	2000-08-04 21:29:31.0	48.92	142.26	33	10	-	5.4/ 5	4.5	Sakhalin, Russia
20001026	2000-08-04 22:11:15.0	48.83	142.33	33	8	-	4.0/ 5	-	Sakhalin, Russia
20001027	2000-08-04 22:21:08.0	48.86	142.48	33	10	-	4.3/ 5	-	Sakhalin, Russia
20001028	2000-08-05 01:13:26.0	48.58	142.56	33	9	4.5/ 5	-	4-4.5	Sakhalin, Russia
20001029	2000-08-05 01:42:30.0	48.88	142.64	33	7	4.1/ 5	3.9/ 2	3.5-4	Sakhalin, Russia
20001031	2000-08-05 06:52:25.0	48.79	142.38	33	8	4.2/ 4	4.4/ 3	3.5-4	Sakhalin, Russia

Macroseismic manifestations

Epicenter of the earthquake was located in Sakhalin island at 200 km to the north from Yuzhno-Sakhalinsk. From data of ITAR TASS and Sakhalin experimental methodical expedition of GS RAS this earthquake was felt in the following places of Sakhalin island: quakes with intensity VI MSK are fixed on west coast near of Uglegorsk, in Makarov, Poronaisk - V MSK, Dolinsk, Ilintsky - IV MSK, Yuzhno-Sakhalinsk - III MSK. Some distractions took place in Nikolsk settlement of Uglegorsk region. Energy supply of living sites was terminated in three regions of central part of Sakhalin. In Uglegorsk region two high voltage lines have been cut. On the east coast of Sakhalin in Poronaisk region three lines of power supply are out of operation. However Sakhalin power plant is in operation and works in normal mode. This earthquake was accompanied with landslides. From data of Far East regional center of Ministry of Accidental Situations one of this landslides has crossed the road between Uglegorsk town and Krasnopolie settlement. Width of the landslide - nearly 200 m, height - 4 m. Another landslide with width 300 m hit the road in the region of Zaozernoe settlement. As a result of underground storm 1390 living houses, 22 industrial objects and 2 other objects have been distracted in the area. In addition 32 km of power supply lines, 5 km of communication lines, 3.3 km of water pipes, 3 km of roads, 1.5 km of heat transfer lines and 16 men have been hit. Three men were sent to hospital. From official information of Russia there are no victims.

Historical records

The earthquake has happened in the south border of seismic active zone, which spreads close to meridian direction in the area between seismic stations Uglegorsk and Timovskoe (fig.3). According to data from the «New catalogue of strong earthquakes on the territory of USSR from ancient times till 1975» and from «Seismological Bulletin of CEME GS RAS» a few strong earthquakes were registered in this zone in the previous hundred years: Lesogorsk-Uglegorsk earthquake on March 15, 1924 with М=6.8 Io=8-9, Uglegorsk earthquake on February 6, 1973 with М=4.7 Io=7 and some others. However no strong earthquakes (with M>4) were observed to the south from the hypocenter of this event at the distance of 100 km within the same period of time. It is necessary to note that hypocenter of this event is located in the seismological zone different from the disastrous Neftegorsk earthquake happened on May 27, 1995 with М=7.7.

Focal mechanism and seismic moment of the earthquake

Table 3 and figure 4 contain solutions of the origin mechanism obtained in Harvard (USA) from centroid moment tensor CMT. Both nodal planes have close to meridian strike (AZ=187 and 327 degrees), corresponding with the length of Sakhalin island from the north to the south and having quite steep slope depth (angels of slope to the horizon make 58 and 39 degrees respectively). Motion is done under the influence of nearly horizontal compressing strengths oriented sublatitudely. Type of motion – left lateral reverse.

Table 2

Axes of main strengths

Nodal planes

Center

NP1

NP2

Azm

Stk

Slip

Stk

Slip

144

260

354

327

187

114

HARVARD

HARVARD - Harvard Geophysical Center (USA)

Figure 4