Information message about the strong earthquake in the Pacific Ocean in the Ryukyu Islands, Japan, February 26, 2010. |
| The strong earthquake with M=7.2 has occurred on February 26, 2010 at 20:31 GMT (February 26 at 23:31 Moscow time) in Pacific Ocean in the region of Ryukyu 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 19 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 68 stations, accurate processing - with data 68 stations. |
| Fig. 1 presents fragments of records obtained from digital stations Vladivostok (∆ 17.3º), Talaya (∆ 31.8º), Petropavlovsk (∆ 35.1º), Yakutsk (∆ 36.0º), Tiksi (∆ 45.6º). Fig. 2 presents fragments of records obtained from digital stations Ala Archa (∆ 46.8º), Bilibino (∆ 47.8º), Borovoe (∆ 50.7º), Arti (∆ 57.7º), Obninsk (∆ 70.2º). |
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 |
20-31-23.8 |
26.04 |
128.58 |
15 |
68 |
7.2/32 | 7.1/34 | 9.5-10 | 73 | IPC GS RAS | | 2 |
20-31-24.8 |
25.93 |
128.48 |
2 |
43 |
7.2 Mw | | | 56 | CSEM | | 3 |
20-31-27.0 |
25.903 |
128.417 |
22 |
281 |
7.0 Mw | 6.7/229 | | 14 | 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 shows with red star epicenter of this earthquake, whose focus was located in the Pacific Ocean off the coast of the Ryukyu Islands, Japan at a depth of 15 km, 91 km east-southeast of Naha in Okinawa. |
Figure 3 |
|
| Aftershock |
| GS RAS has registered 4 aftershocks with М>=5 within 15 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 |
| 20100741 | 2010-02-27 00:48:44.0 | 25.99 | 128.5 | 33 | 22 | 4.6/ 10 | 5.1/ 12 | 4.5 | Ryukyu Islands, Japan | | 20100743 | 2010-02-27 01:33:22.0 | 25.93 | 128.42 | 33 | 14 | - | 5.0/ 10 | 3.5-4 | Ryukyu Islands, Japan | | 20100746 | 2010-02-27 05:37:26.0 | 26.03 | 128.69 | 10 | 21 | - | 5.0/ 16 | 5-5.5 | Ryukyu Islands, Japan | | 20100752 | 2010-02-27 09:38:19.0 | 25.95 | 128.55 | 33 | 17 | - | 5.3/ 14 | 4-4.5 | Ryukyu Islands, Japan | |
| Macroseismic manifestations |
| According to U.S. Geological Survey NEIC this earthquake was felt in Okinawa Island with intensity up to 6 points. Fig. 4, taken from the U.S. Geological Survey presents the map of intensity created with telephone calls obtained from 674 respondents living in 15 localities.
|
Figure 4 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions for this earthquake which happened on Feb. 26, 2010 at 20 hrs 31 min (GMT) were obtained with CMT method in the National Earthquake Information Center U.S. Geological Survey, USGS and with Global CMT Catalog, USA. These solutions are given in Table 2 and shown in figures 5, 6. Solutions are identical. The earthquake occurred under the action of equal expansion and compression forces, oriented northwest-southeast and northeast, respectively. Both nodal planes occur rather abruptly, NP1 plane has latitudinal direction of propagation, NP2 plane – longitudinal. Type of motion along both planes - left-side drift for NP1, right-side drift for NP2.
The value of seismic moment Mo for this earthquake which occurred on Feb. 26, 2010 in accordance with USGS makes 3.4* 10** 19 n*m, the value of moment magnitude Mw=7.0, and in accordance with Global CMT Catalog – Мо= 3.63* 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 |
| 1 | 135 | 14 | 44 |
75 | 229 | 89 | 81 | -10 | 181 |
79 | -169 | NEIC | | 15 | 314 | 11 | 47 |
71 | 170 | 91 | 72 | 3 | 0 |
87 | 161 | Quick CMT | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| Quick CMT - Quick CMT catalog |
Figure 5 | 
Figure 6 |
|
