Information message about the strong earthquake in the region of Nikobar Islands, June 12, 2010 |
| The strong earthquake with M=7.6 has occurred on June 12, 2010 at 19:26 GMT (23:26 Moscow time) in the region of Nikobar Islands, 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 18 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 44 stations, accurate processing - with data 57 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Kurchatov (∆ 44.2º), Talaya (∆ 44.8º), Borovoe (∆ 48.4º), Vladivostok (∆ 49.7º), Garni (∆ 52.9º). Fig. 2 presents fragments of records obtained from digital stations Yakutsk (∆ 60.8º), Obninsk (∆ 64.2º), Tiksi (∆ 67.8º), Pulkovo (∆ 69.2º), Petropavlovsk (∆ 69.9º).
|
Figure 1
| 
Figure 2
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|
| 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 |
19-26-47.6 |
7.8 |
91.85 |
33 |
57 |
7.6/33 | 7.4/34 | 9 | 66 | IPC GS RAS (Accurate) | | 2 |
19-26-46.7 |
7.67 |
91.86 |
33 |
44 |
7.6/27 | 7.5/28 | 9 | 109 | IPC GS RAS (Preliminary) | | 3 |
19-26-46.6 |
7.78 |
91.89 |
10 |
508 |
Mw 7.5 | | | 57 | CSEM | | 4 |
19-26-50.4 |
7.75 |
91.94 |
35 |
110 |
Mw 7.5 | 7/101 | | 58 | NEIC (Accurate) | | 5 |
19-26-50.6 |
7.7 |
91.97 |
35 |
52 |
Mw 7.7 | 7.1/38 | | | 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 depicts with red star epicenter of this earthquake, it's origin was located in Indian Ocean near the western coast of Nikobar Islands, at the depth of 33 km, 165 km W-S-W of Mokheana, India, 455 km S-S-W of Port-Bler, India and 450 km W-N-W of Banda-Achekha, Indonesia. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 8 aftershocks with М>=4.5 in 2 days 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 |
| 20102056 | 2010-06-12 20:12:21.0 | 6.76 | 92.02 | 10 | 10 | - | 4.5/ 9 | 4-4.5 | Nicobar Islands, India region | | 20102058 | 2010-06-12 22:44:40.0 | 7.65 | 91.99 | 33 | 22 | - | 5.4/ 13 | 4.5 | Nicobar Islands, India region | | 20102059 | 2010-06-12 22:58:08.0 | 8.06 | 91.77 | 33 | 18 | - | 5.0/ 14 | 3.5-4 | Nicobar Islands, India region | | 20102063 | 2010-06-13 02:50:35.0 | 7.75 | 92.02 | 33 | 23 | - | 5.0/ 14 | 3.5-4 | Nicobar Islands, India region | | 20102064 | 2010-06-13 04:01:04.0 | 7.8 | 92.08 | 33 | 27 | - | 5.0/ 18 | 3.5-4 | Nicobar Islands, India region | | 20102066 | 2010-06-13 06:26:02.0 | 7.69 | 92.06 | 33 | 18 | - | 5.1/ 14 | 3.5-4 | Nicobar Islands, India region | | 20102067 | 2010-06-13 07:05:34.0 | 7.78 | 91.97 | 33 | 29 | - | 5.3/ 19 | 4-4.5 | Nicobar Islands, India region | | 20102068 | 2010-06-13 07:36:59.0 | 7.57 | 91.99 | 33 | 11 | - | 4.8/ 6 | 3-3.5 | Nicobar Islands, India region | |
| Macroseismic manifestations |
| Fig. 4 obtained from Geological Service USA NEIC , presents the map with intensities base on phone calls to 463 respondents living in 68 places.
|
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of this event with occurred on June 12, 2010 at 19:26 (GMT) was obtained in GS RAS with initial signs of Р-waves arrivals at 164 stations, 100 of these stations registered the waves of compression (plus signs), 64 – the waves of expansion (minus signs). These stations are located in the epicentral distance of 8º-99º with rather uniform distribution along azimuths. Focal mechanism solution of the origin in stereographic projection of lower hemisphere is shown on figure 5, elements of this solution are presented in table. 2. Table 2 and figures 6, 7 also present focal mechanism solutions calculated with CMT technique in NEIC USA, USGS and with method of tensor moment of centroid in Global CMT Catalog, USA.
These solutions are identical. The earthquake has occurred under the action of almost equal expansion and compression forces oriented N-E and N-S respectively. Both nodal planes are rather steeply falling (DP=57º-72º), one of them NP1 propagates from N-E to S-W, another plane NP2 propagates N-W – S-E. The type of motion along both planes – shift with components of uplift, for NP1 – left shift, for NP2 – right shift.
The value of seismic moment Мо for the earthquake which occurred on June 12, 2010 was obtained in IPC GS RAS with spectra of Р-waves recorded at four stations: «Talaya» (∆ 44.94º), «Arti» (∆ 55.22º), «Kislovodsk» (∆ 55.97º), "Obninsk" (∆ 64.36º), it makes Мо=1.1* 10** 20 n*m. Averaged value of moment magnitude Mw calculated from Kanamori formula makes Mw=7.3.
The value of seismic moment Мо in accordance with USGS makes 1.8* 10** 20 n*m, the value of moment magnitude Mw=7.4; in accordance with Global CMT Catalog – Мо=1.86* 10** 20 n*m, Mw=7.4.
|
| 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 |
| 47 | 103 | 20 | 349 |
36 | 243 | 232 | 75 | 52 | 123 |
40 | 156 | IPC GS RAS | | 37 | 72 | 9 | 170 |
50 | 272 | 218 | 57 | 22 | 116 |
72 | 145 | NEIC | | 39 | 79 | 3 | 347 |
51 | 254 | 220 | 66 | 32 | 116 |
61 | 152 | 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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