Information message about destructive earthquake in India on September 18, 2011. |
| The significant earthquake with M=6.6 which caused victims and destructions has occurred on September 18, 2011 at 12:40 GMT (16:40 Moscow time) in India.
|
| 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 15 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 63 stations, accurate processing - with data 66 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Ala Archa (∆ 18.6º), Kurchatov (∆ 24.1), Talaya (∆ 26.6º), Borovoe (∆ 28.6º), Arti (∆ 35.6º). Fig. 2 presents fragments of records obtained from digital stations Obninsk (∆ 46º), Erimo (∆ 46.5º), Tiksi (∆ 49.3º), Lovozero (∆ 51.1º), Petropavlovsk (∆ 56.8º).
|
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 |
12-40-46.5 |
27.74 |
88.21 |
20 |
66 |
6.6/41 | 6.6/41 | 8-8.5 | 69 | IPC GS RAS (Accurate) | | 2 |
12-40-48.4 |
27.74 |
88.21 |
33 |
63 |
6.6/32 | 6.6/33 | 8-8.5 | 69 | IPC GS RAS (Preliminary) | | 3 |
12-40-47.3 |
27.83 |
88.18 |
10 |
736 |
Mw 6.9 | | | 22 | CSEM | | 4 |
12-40-48.0 |
27.72 |
88.06 |
19.7 |
344 |
6.7/452 | 6.6/232 | | 22 | 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 |
| Fig.3 presents with red star epicenter of this earthquake, which origin was located in North-Eastern State Sikkim, India, at the depth of 20 km, 62 km N-W of Gangtok, India, 96 km E-N-E of Ilam, Nepal, 150 km W-N-W of Thimphu, Butane.
|
Figure 3 |
|
| Aftershock |
| GS RS registered 2 aftershocks with М>=4.5 within 1 hour 15 minutes 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 |
| 20114049 | 2011-09-18 13:11:59.0 | 27.52 | 88.78 | 33 | 20 | - | 4.5/ 16 | 2-2.5 | Sikkim, India | | 20114048 | 2011-09-18 13:54:18.0 | 27.39 | 88.36 | 33 | 21 | - | 4.7/ 16 | 2.5-3 | Sikkim, India | |
| Macroseismic manifestations |
| In accordance with data from RIA-Novosti more than 42 people were killed.
Information at the sight of Economic Times paper reports about 19 killed in the North-Eastern state of Sikkim, another five persons were killed in in the state Western Bengali and two persons in Bihar state.
Moreover, nine persons were killed in neighboring Nepal, which also suffered from this earthquake, as reports IANS information agency. Mass media reports about seven victims registered in Chinese Tibet.
Fig. 4 downloaded from US Geological Service NEIC , presents the map of intensities composed with messages from 1198 respondents living in 187 places. |
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of the origin for this earthquake which occurred on September 18, 2011 at 12:40 GMT was calculated moment centroid technique in NEIC USA, and with CMT technique in USGS and Global CMT Catalog, USA.
All solutions are almost identical. Focal mechanism solution of the origin in stereographic projection at the lower hemisphere is presented in figures 5–6, elements if this mechanism are presented in table 2. This earthquake has occurred under the action of both expansion strengths oriented W-E, and compression forces oriented to the south. Both nodal planes are rather steeply falling, NP1 has N-E direction of propagation, NP2 – has N-W direction of propagation, the type of motion along both planes – drift (left side for NP1 and right side for NP2). The value of seismic moment in accordance with USGS makes Мо=2.7*10**19 n*m, the value of moment magnitude makes Mw=6.9, in accordance with Global CMT – Мо=2.78*10**19 n*m, Mw=6.9 |
| 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 |
| 8 | 84 | 8 | 174 |
78 | 309 | 220 | 78 | 0 | 130 |
90 | 168 | NEIC | | 0 | 265 | 24 | 175 |
66 | 356 | 217 | 74 | -18 | 313 |
73 | -163 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
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