Information message about the strong earthquake in the region of Bonin Islands, Japan on December 21, 2010 |
| The strong earthquake with М=7.5 has occurred on December 21, 2010 at 17:19 GMT (20:19 Moscow time) in the region of Bonin Islands of Japan. |
| 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 13 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 50 stations, accurate processing - with data 58 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Matsushiro (∆ 10.6º), Erimo (∆ 14.9º), Mys Shultsa (∆ 18.6º), Vladivostok (∆ 18.7º), Petropavlovsk (∆ 28.2º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 65.3º), Lovozero (∆ 72º), Obninsk (∆ 77.4º), Kislovodsk (∆ 79.1º), Garni (∆ 79.5º). |
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 |
17-19-40.3 |
27.09 |
143.81 |
15 |
50 |
7.5/34 | 7.4/35 | 10-10.5 | 56 | IPC GS RAS (Preliminary) | | 2 |
17-19-40.4 |
27.1 |
143.78 |
15 |
58 |
7.5/37 | 7.4/41 | 10-10.5 | 56 | IPC GS RAS (Accurate) | | 3 |
17-19-41.8 |
26.93 |
143.71 |
20 |
644 |
Mw 7.4 | | | 21 | CSEM | | 4 |
17-19-40 .8 |
26.892 |
143.726 |
14 |
424 |
Mw 7.4 | 7/207 | | 11 | NEIC (Accurate) | | 5 |
17-19-41.0 |
26.866 |
143.739 |
14.9 |
311 |
Mw 7.4 | 7.1/123 | | | 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 was located in Pacific Ocean, near the coastline of Bonin Islands, Japan, at the depth of 10 km, in 155 km to the east of Bonin Islands and in 1020 km S-S-E of Tokyo, Japan. |
Figure 3 |
|
| Aftershock |
| This earthquake was accompanied with aftershocks. GS RAS registered 100 aftershocks with М>4.5 in two days after the main shock. The table presents most significant of them. |
| 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 |
| 20104178 | 2010-12-21 17:41:26.0 | 27.21 | 143.31 | 10 | 31 | - | 5.7/ 21 | 7-7.5 | Bonin Islands, Japan region | | 20104191 | 2010-12-21 20:18:42.0 | 27.14 | 143.15 | 10 | 35 | - | 5.6/ 23 | 6.5-7 | Bonin Islands, Japan region | | 20104202 | 2010-12-21 22:19:55.0 | 26.76 | 143.69 | 10 | 49 | - | 5.5/ 25 | 6.5-7 | Bonin Islands, Japan region | | 20104213 | 2010-12-22 01:31:17.0 | 26.72 | 143.34 | 10 | 49 | - | 5.8/ 36 | 7-7.5 | Bonin Islands, Japan region | | 20104214 | 2010-12-22 01:36:29.0 | 26.74 | 143.62 | 10 | 50 | - | 5.6/ 24 | 6.5-7 | Bonin Islands, Japan region | | 20104231 | 2010-12-22 07:51:43.0 | 26.9 | 143.62 | 10 | 33 | - | 5.6/ 15 | 6.5-7 | Bonin Islands, Japan region | | 20104246 | 2010-12-22 13:01:11.0 | 27.01 | 143.27 | 10 | 48 | - | 5.6/ 27 | 6.5-7 | Bonin Islands, Japan region | | 20104257 | 2010-12-22 21:49:36.0 | 26.75 | 143.65 | 10 | 63 | 6.3/ 21 | 6.5/ 26 | 8.5-9 | Bonin Islands, Japan region | |
| Macroseismic manifestations |
| There were messages neither about victims nor destructions as a result of this earthquake. In accordance with NEIC USA this earthquake was felt in Japanese cities with intensity of 4 MSK. Pacific Center issued warning message about the risk of potential tsunami for the nearest islands, however later this tsunami risk message was cancelled. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of this earthquake which occurred on December 21, 2010 at 17:19 GMT was obtained in IPC GS RAS with first signs of P-wave arrivals at 193 stations, including 13 stations which registered the waves of compression (plus signs), and 180 stations which registered the waves of expansion (minus signs). These stations are located in epicenter distances of 1º-98º between them with rather uniform dispersion along the azimuths. Focal mechanism solution of the origin is presented in figure 4 in stereographic projection at lower hemisphere, elements of this mechanism are presented in table 2. Table 2 and figures 5, 6 also present focal mechanism solutions of the origin, which were calculated with CMT method in NEIC USA, USGS and Global CMT Catalog, USA. All solutions obtained in these three centers with various techniques are almost similar. This earthquake has occurred under the action of N-E oriented expansion forces. The type of motion along both nodal planes – fault with shift components (right side components for NP1 and left side for NP2). NP1 plane in USGS and CMT solutions lay more flat (DP=34º-42º) with rather steeply falling NP2 (DP=58º-70º). Flat plane NP1 has S-E– latitudinal direction of propagation, while steeply falling NP2 plane is nearly along meridian direction of propagation.
Seismic moment of this earthquake which occurred on December 21, 2010 was calculated in IPC GS RAS with Р-wave spectra obtained at three stations: «Arti» (∆ 65.31º), «Obninsk» (∆ 77.36º) and «Kislovodsk» (∆ 79.10º), it makes Мо=1.9*10**20 n*m. Averaged value of moment magnitude Mw calculated with Kanamori formula makes Mw=7.5.
The value of seismic moment Мо for this earthquake which occurred on December 21, 2010 in accordance with USGS makes 1.9*10**20 n*m, the value of moment magnitude Mw=7.5, and in accordance with Global CMT Catalog – Мо=1.43*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 |
| 0 | 63 | 54 | 333 |
36 | 153 | 123 | 55 | -136 | 4 |
55 | -44 | IPC GS RAS | | 20 | 56 | 55 | 294 |
27 | 157 | 108 | 34 | -143 | 347 |
70 | -61 | NEIC | | 9 | 50 | 65 | 301 |
23 | 144 | 115 | 42 | -127 | 340 |
58 | -62 | 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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