Information message about the strong earthquake near the eastern ciast of Honshu Island, Japan, April 7, 2011. |
| The strong earthquake with M=7.2 has occurred on April 7, 2011 at 14:32 GMT (18:32 Moscow time) near the eastern coast of Honshu Island, Japan. |
| Preliminary processing has been done with data from 60 stations, accurate processing - with data 74 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Erimo (∆ 3.8º), Kurilsk (∆ 8.3º), Kuldur (∆ 13.1º), Severo-Kurilsk (∆ 16º), Petropavlovsk (∆ 18.8º). Fig. 2 presents fragments of records obtained from digital stations Borovoe (∆ 50º), Arti (∆ 55.6º), Lovozero (∆ 61º), Obninsk (∆ 67.2º), Kislovodsk (∆ 70.3º). |
Figure 1
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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 |
14-32-40.8 |
38.34 |
141.79 |
33 |
74 |
7.2/40 | 7.2/46 | 8-8.5 | 52 | IPC GS RAS (Accurate) | | 2 |
14-32-40.6 |
38.35 |
141.8 |
33 |
60 |
7.2/35 | 7.2/38 | 8-8.5 | 52 | IPC GS RAS (Preliminary) | | 3 |
14-32-44.3 |
38.29 |
141.63 |
50 |
739 |
Mw 7.1 | | | 31 | CSEM | | 4 |
14-32-41.5 |
38.25 |
141.64 |
25.6 |
426 |
Mw 7.4 | 6.9/118 | | 32 | 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 at the eastern coast of Honshu Island, Japan, at the depth of 33 km., 80 km east off Sendai, 290 km S-S-E off Aomori and 342 km N-E off Tokyo. |
Figure 3 |
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| Macroseismic manifestations |
| In accordance with Channel 1 the strong earthquakes were felt in half of Japanese prefectures including Tokyo. The witnesses talked about oscillating skyscrapers. Miyagi, Ivate and Fukusima prefecture were influenced most of all. Waves of electricity power interrupts were noticed. More than 3,5 million of houses were left without light. In accordance with latest data two persons were killed and 130 suffered. Car and train motion was stopped at all highways and railroads. Some trains stopped in tunnels. TV channel NHK reported about fire in airport of Yamagata prefecture.
"Nuclear power plants Higisidari and Onagawa were shut down immediately after underground shocks; personnel fighting with radioactive leakage at Fukushima NPP was evacuated", - this was reported by official representative of Japanese Agency of Nuclear and Industrial Safety.
Leakage of radioactive water was registered at "Onagawa" NPP. This was the leakage from pools with used fuel located near the first and second reactor units. However representatives of operator company immediately confirmed that there is no risk of contamination.
In Russia this earthquake was felt in Yuzhno-Kurilsk with intensity 2 MSK.
Fig. 5, shared from NEIC USA site presents the map with intensities composed with phone calls to 96 respondents living in 50 places. |
Figure 4 |
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| Historical records |
| This earthquake is the strongest aftershock from destructive earthquake of March 11, 2011 ,which occurred in 80 km to the east with magnitude M=8.8. |
Figure 5 |
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| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions of the origin of this earthquake which occurred on April 7, 2011 at 14:32 GMT were obtained with CMT technique in NEIC USA, USGS and with Global CMT Catalog, USA.
Focal mechanism solutions are almost identical. Focal solution of the origin is presented at figures 5-5 in stereographic projection at lower hemisphere, elements of this solution are presented in table 2. This earthquake occurred under the action of both expansion and compression forces oriented N-W-S-E. Both nodal planes have N-E direction of propagation and are rather steeply falling (DP=37º-53º), the type of motion – uplifts with slide components (right side for NP1 and left side for NP2) . The value of seismic moment of this earthquake which occurred on April 7, 2011 in accordance with USGS makes Мо=6.1*10**19 n*m, The value of moment magnitude makes Mw=7.1, in accordance with Global CMT – Мо=5.91*10**19 n*m, Mw=7.1
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| 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 |
| 83 | 174 | 4 | 294 |
6 | 25 | 210 | 49 | 98 | 18 |
42 | 81 | NEIC | | 80 | 147 | 8 | 295 |
5 | 25 | 209 | 53 | 96 | 19 |
37 | 82 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 6 | 
Figure 7 |
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