Announcement of the strong earthquake off the east coast of Honshu, Japan, July 10, 2011. |
| A strong earthquake with M = 7.3 occurred on July 10, 2011 at 00:57 UTC (4:57 Moscow time) near the eastern coast of Honshu Island, 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 15 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 35 stations, accurate processing - with data 64 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Erimo (∆ 3.9º), Matsushiro (∆ 4.5º), Mys Shultsa (∆ 10.4º), Kuldur (∆ 13.9º), Severo-Kurilsk (∆ 15.5º). Fig. 2 presents fragments of records obtained from digital stations Arti (∆ 56.6º), Lovozero (∆ 61.8º), Obninsk (∆ 68.2º), Kislovodsk (∆ 71.4º), Garni (∆72.4º). |
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 |
00-57-10.1 |
38.14 |
143.43 |
33 |
64 |
7.3/33 | 7.1/36 | 8.5-9 | 52 | IPC GS RAS (Accurate) | | 2 |
00-57-09.3 |
38.33 |
143.45 |
5 |
35 |
| 6.9/22 | 11-11.5 | 84 | IPC GS RAS (Preliminary) | | 3 |
00-57-13.2 |
38.05 |
143.29 |
40 |
646 |
Mw 7.1 | | | 20 | CSEM | | 4 |
00-57-12.7 |
38.04 |
143.29 |
18 |
310 |
Mw 7 | 6.8/126 | | 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 near the eastern coast of Honshu Island, Japan, at the depth of 33 km, 220 km E off Sendai and 420 km E-N-E off Tokyo, the Capital of Japan. |
Figure 3 |
|
| Aftershock |
| GS RAS registered 10 aftershocks with M>=4.7 within 28 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 |
| 20113169 | 2011-07-10 03:14:14.0 | 38.24 | 143.33 | 33 | 26 | - | 4.9/ 17 | 3-3.5 | Off east coast of Honshu, Japan | | 20113170 | 2011-07-10 03:43:33.0 | 38.06 | 143.39 | 33 | 34 | - | 5.1/ 13 | 3.5-4 | Off east coast of Honshu, Japan | | 20113171 | 2011-07-10 04:18:15.0 | 36.06 | 139.96 | 33 | 16 | - | 4.9/ 9 | 3-3.5 | Eastern Honshu, Japan | | 20113173 | 2011-07-10 05:14:33.0 | 38.13 | 143.22 | 33 | 38 | - | 5.0/ 20 | 3.5-4 | Off east coast of Honshu, Japan | | 20113174 | 2011-07-10 05:24:41.0 | 38.06 | 143.41 | 33 | 34 | - | 5.0/ 14 | 3.5-4 | Off east coast of Honshu, Japan | | 20113180 | 2011-07-10 19:16:38.0 | 37.07 | 142.18 | 33 | 13 | - | 5.0/ 4 | 3.5-4 | Off east coast of Honshu, Japan | | 20113181 | 2011-07-10 20:19:05.0 | 38.21 | 144.04 | 33 | 23 | - | 4.9/ 8 | 3-3.5 | Off east coast of Honshu, Japan | | 20113182 | 2011-07-11 00:09:12.0 | 37.12 | 140.96 | 33 | 21 | - | 4.7/ 11 | 2.5-3 | Eastern Honshu, Japan | | 20113184 | 2011-07-11 01:36:02.0 | 38.43 | 142.33 | 33 | 35 | - | 5.0/ 11 | 3.5-4 | Near east coast of Honshu, Japan | | 20113185 | 2011-07-11 04:29:24.0 | 39.31 | 142.04 | 33 | 44 | - | 5.4/ 19 | 4.5 | Near east coast of Honshu, Japan | |
| Macroseismic manifestations |
| According to RIA-Novosti after the earthquake the tsunami threat with a wave height of 0.5 meters has been declared, but tsunami wave with height of 10 centimeters was observed all along the northeastern coast of Japan. Two hours after the earthquake, the tsunami threat has been canceled.
"Fukushima" NPP personnel was instructed to evacuate from the station. Representatives of company-station operator TEPCO reported no damage in connection with the new earthquake. Information about the destruction and injuries was not obtained.
Fig. 4 was downloaded from Website USGS NEIC , presents the map of the intensity obtained with phone calls to 88 respondents living in 34 places. In Russia the earthquake was felt with intensity 3 at Malokurilsk. |
Figure 4 |
|
| Historical records |
| The earthquake occurred in 67 km E-S-E off destructive earthquake of March 11, 2011 with magnitude M=8.8 (fig.5).
|
Figure 5 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solution of the origin for this earthquake which occurred on July 10, 2011 at 00:57 UTC was calculated in IPC GS RAS by the signs of initial arrival of longitudinal waves at 121 stations, meanwhile 50 of them registered compression waves (plus sign) and 71 - dilution waves (minus signs). The stations are located in the range of epicentral distances of 3º -90º, almost uniformly in azimuth. Focal mechanism in the stereographic projection on lower hemisphere is shown in figure 6, the elements of the mechanism are presented in table. 2. Table 2 and figures 7 and 8 also present focal mechanism solutions calculated from the moment of centroid at National Earthquake Information Center U.S. Geological Survey, USGS, and by the method of moment tensor in the Global CMT Catalog, USA.
Solutions are close. The earthquake occurred close to the action of the tensile and compressive stresses oriented in the direction west-north-west and south-west-north-east respectively. Both nodal planes are fairly steep drop - (DP = 80º -89º) and (DP = 58º -80º). One nodal plane extends in a northwesterly direction, the other - in the northeast. Type of movement in both planes - the shift (right-to left-side of NP1 and NP2). It is necessary to note that the type of motion in the origin of the earthquke of March 11, 2011 was different - uplift along the steeply falling plane and thrust along the flat plane.
The seismic moment of the earthquake of July 10, 2011 obtained in IPC GS RAS with spectra of P waves at "Arti» (Δ 56.60 º) and "Obninsk» (Δ 68.16 º) stations makes Mo = 2.3 * 10 ** 19 n*m . The average value of moment magnitude calculated by Kanamori formula makes Mw = 6.9. According to the USGS - Mo = 3.8 * 10 ** 19 n * m, Mw = 7.0, according to the Global CMT - Mo = 3.95 * 10 ** 19 n * m, Mw = 7.0.
|
| 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 |
| 11 | 283 | 3 | 192 |
78 | 88 | 327 | 80 | 174 | 58 |
84 | 10 | IPC GS RAS | | 23 | 283 | 22 | 23 |
58 | 152 | 333 | 89 | 148 | 64 |
58 | 1 | NEIC | | 21 | 287 | 6 | 19 |
68 | 124 | 332 | 80 | 161 | 65 |
71 | 11 | 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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