Information message about the earthquake on September 25, 2003 in the North of Japan near Hokkaido Island |
| Destructive earthquake with magnitude M=8.4 has happened on 25 September, 2003 in northern part of the Japanese region, near island Hokkaido. Earthquake was accompanied a tsunami on all coast of the Japanese islands. It was felt also in Russia, in the south of Kuriles.
|
| 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 39 min after
registration to the Ministry of Emergency of the Russian Federation (EMERCOM). |
| Preliminary processing has been done with data from 23 stations, accurate processing - with data 34 stations. |
| 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 |
19-50-09.60 |
42 |
143 |
40 |
34 |
8.40/12 | 7.30/10 | 9.5-10 | | IPC GS RAS (accurate) | | 2 |
19-50-13.10 |
43 |
143 |
33 |
23 |
8.5/11 | 7.3/9 | 10-11 | | IPC GS RAS (preliminary) | | 3 |
19-50-05.9 |
42 |
143 |
10 |
343 |
8.2 | 6.9 | | 57 | CSEM | | 4 |
19-50-09.52 |
42 |
143 |
33 |
145 |
| 6.3/78 | | 27 | NEIC (preliminary) | | 5 |
19-50-07.43 |
41 |
143 |
33 |
185 |
8.1/106 | 6.5/100 | | 33 | NEIC (accurate) | | 6 |
19-50-14.00 |
42 |
143 |
30 |
322 |
8.1 | 7.2/43 | | | ORFEUS (accurate) | | 7 |
19-50-14.00 |
42 |
143 |
30 |
322 |
| 7.2/43 | | | ORFEUS (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 |
| ORFEUS - Observatories and Research Facilities for EUropean Seismology |
| Aftershock |
| By 16 hours of Moscow time (12pm GMT) on September 26 Alert Survey of GS RAS registered 12 aftershocks for this earthquake, most of them with magnitude 5. |
| 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 |
| 20031391 | 2003-09-25 20:10:04.0 | 42.2 | 143.57 | 33 | 16 | - | 6.0/ 6 | 6 | Hokkaido, Japan region | | 20031392 | 2003-09-25 20:57:15.0 | 42.2 | 143.51 | 33 | 17 | - | 6.1/ 6 | - | Hokkaido, Japan region | | 20031393 | 2003-09-25 21:02:55.0 | 42.38 | 144.17 | 33 | 12 | - | 5.9/ 5 | 5.5-6 | Hokkaido, Japan region | | 20031394 | 2003-09-25 21:08:03.0 | 42.34 | 143.49 | 40 | 19 | - | 6.4/ 7 | 6.5-7 | Hokkaido, Japan region | | 20031395 | 2003-09-25 22:20:20.0 | 42.06 | 143.73 | 33 | 15 | - | 5.8/ 4 | 5.5 | Hokkaido, Japan region | | 20031396 | 2003-09-25 23:11:38.0 | 42.32 | 145.01 | 33 | 12 | - | 5.2/ 4 | - | Hokkaido, Japan region | | 20031398 | 2003-09-26 01:39:15.0 | 42.03 | 143.78 | 50 | 13 | - | 5.0/ 4 | 3 | Hokkaido, Japan region | | 20031399 | 2003-09-26 02:35:18.0 | 42.68 | 144.27 | 50 | 13 | 5.7/ 8 | 6.0/ 5 | 5.5-6 | Hokkaido, Japan region | | 20031400 | 2003-09-26 03:29:22.0 | 42.94 | 143.47 | 130 | 13 | - | 4.6/ 9 | - | Hokkaido, Japan region | | 20031401 | 2003-09-26 03:51:48.0 | 43.07 | 144.53 | 110 | 13 | - | 5.6/ 5 | - | Hokkaido, Japan region | | 20031403 | 2003-09-26 06:26:58.0 | 42.56 | 144.55 | 33 | 19 | 6.0/ 11 | 5.9/ 7 | 6.5-7 | Hokkaido, Japan region | | 20031404 | 2003-09-26 10:11:05.0 | 42.32 | 144.45 | 80 | 7 | - | 4.5/ 5 | - | Hokkaido, Japan region | |
| Historical records |
| The earthquake on September 25, 2003 has happened in seismic active region. This is depicted on map downloaded from WEB site of NEIC, USA (fig.1). The strongest earthquakes have been registered here on March 4, 1952 with М=8.6; May 16, 1968 with М=7.9; January 15, 1993 with М=7.6 (according to NEIC) |
Figure 1 |
|
| Focal mechanism and seismic moment of the earthquake |
| Focal mechanism solutions for origin place of the earthquake 25.09.2003 have been calculated with CMT method in different centers - National Earthquakes Information Center of Geological Service of the USA (NEIC) and in Harvard Center HARVARD (USA). They are presented in table 3 and shown on figures 2-3.
Solutions obtained in different centers are similar. Motion in the earthquake’s origin occurred under the action of expansion and compression strengths oriented to the North-West - South-East directions. Plane NP1 has near to latitudinal direction and is flat-lying, motion along this plane is characterized by right sided over thrust; plane NP2 is steep falling, oriented to the North-East, motion along this plane is thrust. Averaged value of seismic moment Мо determined in IPC GS RAS from Р-wave spectra at seismic stations "Arti" (delta 54 degrees),"Obninsk" (delta 65 degrees) and "Kislovodsk" (delta 69 degrees), makes 1.2* 10** 21 n*m. Moment magnitude from this sources of data makes Mw = 8.0 .
According to NEIC seismic moment Мо makes 1.6* 10** 21 n*m, moment magnitude - Mw = 8.1.
According to HARVARD seismic moment Мо makes 3.0* 10** 21 n*m, moment magnitude - Mw = 8.3.
|
| 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 |
| 51 | 319 | 38 | 126 |
6 | 221 | 178 | 9 | 47 | 42 |
83 | 96 | NEIC | | 52 | 286 | 37 | 123 |
8 | 27 | 252 | 11 | 136 | 25 |
83 | 82 | HARVARD | |
| NEIC - National Earthquakes Information Center of US Geological Service |
| HARVARD - Harvard Geophysical Center (USA) |
Figure 2 | 
Figure 3 |
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