Information message about the strong earthquake near the eastern coast of Honshu Island, Japan, March 9, 2011. |
| The strong earthquake with M=7.7 occurred near the eastern coast of Honshu Island, Japan on March 9, 2011 at 02:45 GMT (05:45 Moscow time). |
| 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 43 stations, accurate processing - with data 53 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Erimo (∆ 3.4º), Kurilsk (∆ 7.6º), Severo-Kurilsk (∆ 15.3º), Ulaanbaatar (∆ 27.5º), Talaya (∆ 30.2º). Fig. 2 presents fragments of records obtained from digital stations Bilibino (∆ 32.2º), Borovoe (∆ 50.4º), Arti (∆ 55.9º), Lovozero (∆ 61.1º), Obninsk (∆ 67.5º). |
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 |
02-45-19.7 |
38.65 |
142.86 |
33 |
53 |
7.7/24 | 6.8/38 | 9-9.5 | 84 | IPC GS RAS (Accurate) | | 2 |
02-45-19.5 |
38.64 |
142.88 |
33 |
43 |
7.4/9 | 6.8/31 | 8.5-9 | 84 | IPC GS RAS (Preliminary) | | 3 |
02-45-17.3 |
38.517 |
142.808 |
9.1 |
428 |
Mw 7.2 | | | 35 | CSEM | | 4 |
02-45-18.2 |
38.509 |
142.792 |
14.1 |
464 |
Mw 7.2 | 6.5/287 | | 29 | 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 was located at the eastern coast of Honshu Island, Japan, at the depth of 33 kilometers, 175 km N-N-E off Sendai, 300 km S-E off Aomori and 424 km N-E off Tokyo. |
Figure 3 |
|
| Aftershock |
| This earthquake was accompanied with aftershocks. The presented table contains 12 of most significant aftershocks with M>5, which were registered by GS RAS within 6 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 |
| 20110858 | 2011-03-09 02:57:14.0 | 38.45 | 143.25 | 33 | 38 | - | 6.0/ 21 | 6 | Off east coast of Honshu, Japan | | 20110859 | 2011-03-09 03:08:34.0 | 38.25 | 143.27 | 33 | 44 | - | 5.5/ 21 | 4.5-5 | Off east coast of Honshu, Japan | | 20110857 | 2011-03-09 03:18:58.0 | 38.7 | 143.2 | 33 | 47 | - | 5.2/ 23 | 4-4.5 | Off east coast of Honshu, Japan | | 20110861 | 2011-03-09 04:05:52.0 | 38.66 | 142.98 | 33 | 25 | - | 5.3/ 19 | 4-4.5 | Near east coast of Honshu, Japan | | 20110862 | 2011-03-09 04:32:06.0 | 38.76 | 143.2 | 33 | 51 | - | 5.5/ 18 | 4.5-5 | Off east coast of Honshu, Japan | | 20110863 | 2011-03-09 04:37:03.0 | 38.87 | 142.99 | 33 | 54 | - | 5.8/ 25 | 5.5 | Near east coast of Honshu, Japan | | 20110864 | 2011-03-09 04:45:53.0 | 38.87 | 142.7 | 33 | 53 | - | 5.7/ 25 | 5-5.5 | Near east coast of Honshu, Japan | | 20110865 | 2011-03-09 05:27:20.0 | 38.59 | 143.25 | 33 | 30 | - | 5.1/ 18 | 3.5-4 | Off east coast of Honshu, Japan | | 20110867 | 2011-03-09 06:25:12.0 | 38.29 | 143.19 | 33 | 49 | - | 5.6/ 26 | 5 | Off east coast of Honshu, Japan | | 20110868 | 2011-03-09 07:13:49.0 | 38.32 | 143.23 | 33 | 43 | - | 5.3/ 24 | 4-4.5 | Off east coast of Honshu, Japan | | 20110869 | 2011-03-09 07:56:27.0 | 38.79 | 143.15 | 33 | 45 | - | 5.4/ 28 | 4.5 | Off east coast of Honshu, Japan | | 20110870 | 2011-03-09 08:02:36.0 | 38.71 | 143.16 | 33 | 47 | - | 5.5/ 17 | 4.5-5 | Off east coast of Honshu, Japan | |
| Macroseismic manifestations |
| In accordance with Channel 1 the strong shocks were felt in a half of all Japanese prefectures including Tokyo. From the latest news there are neither victims nor destructions. It is known that in one town the school house was partially destroyed. Speed rail traffic was stopped for a few hours for safety reasons. It is reported that this earthquake influenced the operation of two nuclear power plants in Miyagi Prefecture, which is very close to the epicenter. Experts warned about the risk of tsunami, but the waves originated from this earthquake had only 60 centimeters in height. In Russia this earthquake was felt only in Yuzhno-Kurilsk with intensity of 2 MSK. |
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution for this earthquake which occurred on March 9, 2011 at 02:45 GMT was calculated with CMT method in NEIC USA, USGS and Global CMT Catalog, USA.
Focal mechanism solution in stereographic projection at lower hemisphere is presented in figures 4, 5, elements of this mechanism are presented in table 2.
All focal solutions are identical. This earthquake occurred under the action of prevailing both expansion and compression forces oriented in N-W-S-E direction. Both nodal planes have N-E direction of propagation, one of them is steeply falling, almost vertically (DP=76º–83º), another is flat (DP=7º-14º). The type of motion along steeply falling plane – uplift, and along the flat plane – overthrust with small left side slip component along the flat plane.
Seismic moment of this earthquake which occurred on March 9, 2011 was calculated in GS RAS from Р-wave spectra obtained at four stations: «Talaya» (∆ 30.17º), «Arti» (∆ 55.93º), «Obninsk» (∆ 67.51º), «Kislovodsk» (∆ 70.73º), it makes Мо=1.4*10**20 n*m. Averaged value of Mw was calculated with Kanamori formula and makes Mw=7.4.
In accordance with USGS the value of seismic moment for this earthquake makes Мо=9.9*10**19 n*m and the value of moment magnitude makes Mw=7.3. In accordance with Global CMT Catalog the value of seismic moment for this earthquake makes Мо=2.1*10**20 n*m and the value of moment magnitude makes Mw=7.5.
|
| 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 |
| 59 | 294 | 30 | 109 |
2 | 200 | 192 | 14 | 81 | 21 |
76 | 92 | NEIC | | 52 | 294 | 38 | 111 |
2 | 202 | 190 | 7 | 78 | 23 |
83 | 92 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 4 | 
Figure 5 |
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