Information message about the strong earthquake near the western coast of South Sumatra, Indonesia, October 25, 2010. |
| The strong earthquake with М=7.4 has occurred on October 25, 2010 at 14:42 GMT (18:42 Moscow time) in Indonesia near the western coast of South Sumatra island. |
| 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 18 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 55 stations, accurate processing - with data 66 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Tennant Creek (∆ 37.2º), Port Moresby (∆ 47.1º), Ala Archa (∆ 51.5º), Matsushiro (∆ 53.4º), Mys Shultsa (∆ 53.8º). Fig. 2 presents fragments of records obtained from digital stations Erimo (∆ 59.8º), Yuzhno-Kurilsk (∆ 62.6º), Garni (∆ 66.7º), Kislovodsk (∆ 69.8º), Obninsk (∆ 78.1º). |
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 |
14-42-19.6 |
-3.49 |
100.13 |
20 |
66 |
7.4/32 | 6.4/32 | 9.5 | 79 | IPC GS RAS (Accurate) | | 2 |
14-42-18.0 |
-3.51 |
100.14 |
10 |
55 |
7.3/24 | 6.4/22 | 10.5 | 79 | IPC GS RAS (Preliminary) | | 3 |
14-42-21.4 |
-3.47 |
100.12 |
10 |
450 |
Mw 7.6 | | | 23 | CSEM | | 4 |
14-42-22.7 |
-3.48 |
100.11 |
20 |
297 |
Mw 7.7 | 6.5/109 | | 22 | NEIC (Accurate) | | 5 |
14-42-22.2 |
-3.46 |
100.08 |
14 |
258 |
7.0/15 | 6.6/100 | | | NEIC (Preliminary) | |
| 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 with red star epicenter of this earthquake, which origin place was located in sea near the coast of North Sumatra, at the depth of 20 km, 280 km S-S-W of Padang, Indonesia, and 520 km W-S-W of Palembang, Indonesia. |
Figure 3 |
|
| Aftershock |
| This earthquake was accompanied with aftershocks. GS RAS registered 14 aftershocks with М>=4.9 within 18 hours after the main shock. |
| 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 |
| 20103483 | 2010-10-25 15:21:07.0 | -3.41 | 99.86 | 10 | 21 | - | 5.2/ 14 | 5.5-6 | Southwest of Sumatera, Indonesia | | 20103484 | 2010-10-25 15:31:07.0 | -3.18 | 100.02 | 10 | 20 | - | 5.1/ 4 | 5.5-6 | Southern Sumatera, Indonesia | | 20103485 | 2010-10-25 15:55:55.0 | -3.59 | 99.66 | 20 | 20 | - | 4.9/ 10 | 4-4.5 | Southwest of Sumatera, Indonesia | | 20103486 | 2010-10-25 17:36:37.0 | -3.07 | 99.37 | 20 | 19 | - | 4.9/ 17 | 4-4.5 | Southwest of Sumatera, Indonesia | | 20103487 | 2010-10-25 18:40:29.0 | -3.38 | 100.18 | 33 | 22 | - | 5.1/ 11 | 3.5-4 | Southern Sumatera, Indonesia | | 20103488 | 2010-10-25 19:37:28.0 | -2.83 | 100.41 | 20 | 63 | 6.1/ 22 | 6.3/ 24 | 7.5-8 | Southern Sumatera, Indonesia | | 20103489 | 2010-10-25 19:33:27.0 | -3.54 | 99.65 | 33 | 23 | - | 5.0/ 10 | 3.5-4 | Southwest of Sumatera, Indonesia | | 20103491 | 2010-10-25 19:57:54.0 | -3.22 | 100.57 | 33 | 17 | - | 5.0/ 7 | 3.5-4 | Southern Sumatera, Indonesia | | 20103492 | 2010-10-25 22:59:50.0 | -3.3 | 100.5 | 20 | 42 | 6.0/ 17 | 6.0/ 23 | 7-7.5 | Southern Sumatera, Indonesia | | 20103493 | 2010-10-25 20:22:15.0 | -2.9 | 99.87 | 20 | 16 | - | 5.0/ 9 | 4-4.5 | Southern Sumatera, Indonesia | | 20103494 | 2010-10-25 22:10:01.0 | -2.73 | 100.04 | 20 | 37 | - | 5.1/ 15 | 4.5-5 | Southern Sumatera, Indonesia | | 20103496 | 2010-10-26 03:28:29.0 | -3.13 | 100.42 | 20 | 23 | - | 5.1/ 12 | 4.5-5 | Southern Sumatera, Indonesia | | 20103497 | 2010-10-26 03:50:11.0 | -3.02 | 100.1 | 10 | 13 | - | 5.0/ 6 | 5-5.5 | Southern Sumatera, Indonesia | | 20103500 | 2010-10-26 08:53:14.0 | -3.63 | 99.66 | 33 | 23 | - | 5.1/ 16 | 3.5-4 | Southwest of Sumatera, Indonesia | |
| Macroseismic manifestations |
| Fig. 4 obtained from WEB site of NEIC USA , presents the map of intensities composed after phone calls to 15 respondents living in 6 places.
From information of RIA Novosti this earthquake caused local tsunami, which has fallen on Mentavei Islands with waves having height from 3 to 7 meters. The Governor of Western Sumatra Mr. Irvan Praitno has reported to Antara National Information Agency that the number of victims reached 112 persons and the destiny of other 502 persons is unknown.
|
Figure 4 |
|
| Historical records |
| Epicenter of this earthquake was located in 295 km S-S-E of epicenter place belonging to destructive earthquake on September 30, 2009 with М=7.4 |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution for the origin of this earthquake which occurred on October 25, 2010 at 14:42 GMT was calculated in IPC GS RAS with first signs of initial arrivals of P waves at 124 stations, including 107 stations which registered the waves of compression (plus signs), and 17 stations – which registered the waves of expansion (minus signs). These stations are located in the interval of epicenter distances of 6º-99º with their rather uniform distribution along the azimuth. Focal mechanism of in stereographic projection of lower hemisphere is presented in figure 5, elements of this mechanism are presented in table 2. Table 2 and fig. 6, 7 also present focal mechanism solutions of the origin, witch were calculated with CMT method in NEIC USA, USGS and Global CMT Catalog, USA All solutions are almost identical. This earthquake has occurred under prevailing action of S-W oriented compression forces. Nodal plane NP1 was laying flat (DP=7º-12º) with N-W direction of propagation nearly along meridian. Nodal plane NP2 was steeply falling (declination angle DP=78º-84º) with N-W direction of propagation. The type of motion along the flat plane is characterized as thrust, and as uplift along the steeply falling plane.
Seismic moment of the earthquake October 25, 2010 was calculated in IPC GS RAS with spectra of Р-waves registered at three stations: «Talaya» (∆ 55.04º), «Kislovodsk» (∆ 69.76º), "Obninsk" (∆ 78.12º), it makes Мо=6.4* 10** 19 n*m. Averaged value of moment magnitude Mw was calculated with Kanamori formula and it makes Mw=7.2.
The value of seismic moment Мо in accordance with USGS makes 4.0* 10** 20 n*m, the value of moment magnitude makes Mw=7.7. The value of seismic moment Мо in accordance with Global CMT Catalog – Мо=6.66* 10** 20 n*m and Mw=7.8. |
| 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 |
| 50 | 27 | 38 | 226 |
9 | 20 | 4 | 11 | 146 | 128 |
84 | 81 | IPC GS RAS | | 57 | 41 | 33 | 226 |
2 | 135 | 326 | 12 | 101 | 134 |
78 | 87 | NEIC | | 52 | 40 | 38 | 222 |
1 | 132 | 319 | 7 | 98 | 131 |
83 | 89 | Quick CMT | |
| IPC GS RAS - Informational Processing Center, Geophysical Survey, Russian Academy of Sciences |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
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