Information message about the strong earthquake near the eastern coast of Honshu Island, Japan, May 7, 2008

     The strong earthquake with M=7.3 has occured on May 7, 2008 at 16:45 GMT (20:45 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 50 min after registration to the Ministry of Emergency of the Russian Federation (EMERCOM).
     Preliminary processing has been done with data from 37 stations, accurate processing - with data 48 stations.
     Fig. 1 presents fragments of records obtained from digital stations Petropavlovsk (∆ 20.5º), Yakutsk (∆ 26.7º), Seimchan (∆ 27.4º), Ulan-Bator (∆ 27.8º), Talaya (∆ 30.8º). Fig. 2 presents fragments of records obtained from digital stations Tiksi (∆ 35.9º), Kurchatov (∆ 46.4º), Borovoe (∆ 51.1º), Arti (∆ 56.9º), Obninsk (∆ 68.7º).

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 16-45-19.0 36.43 141.59  33  48  7.3/196.6/268.5-9 141 IPC GS RAS (Accurate)
2 16-45-18.0 36.27 141.62  33  37  7.3/126.6/178.5-9 141 IPC GS RAS (Preliminary)
3 16-45-18.3 36.2 141.47  33  283  6.7Mw   37 CSEM
4 16-45-21.5 36.14 141.46  45  201  7.1Mw/16.0/185  NEIC (Preliminary)
5 16-45-20.3 36.14 141.45  35  122  6.8Mw 6.1/118 36 NEIC (Accurate)
  • 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 downloaded from NEIC USA depicts epicenter of this earthquake, which was located in Pacific Ocean near the eastern coast of Honshu Island, Japan, in 90 km to the east-south-east from Mito and in 160 km to the east-north-east from Tokyo.

    Figure 3
    Aftershock
         Within the day after the main shock GS RAS registered 18 additional earthquakes in this region:7 foreshocks (the strongest – with magnitude М=6.5) and 11 aftershocks.
    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
    200814622008-05-07 09:59:06.036.63141.4733264.6/ 115.2/ 144.5 Near east coast of Honshu, Japan
    200814632008-05-07 10:49:59.036.69141.6333224.3/ 84.7/ 94-4.5 Near east coast of Honshu, Japan
    200814642008-05-07 11:09:03.036.35141.833326-5.2/ 134-4.5 Near east coast of Honshu, Japan
    200814652008-05-07 15:25:16.036.65141.63319-5.1/ 123.5-4 Near east coast of Honshu, Japan
    200814662008-05-07 16:02:00.036.33141.6210366.5/ 126.5/ 159-9.5 Near east coast of Honshu, Japan
    200814682008-05-07 16:12:25.036.29141.833326-5.7/ 125-5.5 Near east coast of Honshu, Japan
    200814692008-05-07 16:16:36.036.33141.773329-6.3/ 116.5-7 Near east coast of Honshu, Japan
    200814702008-05-07 17:21:03.036.29141.223317-5.0/ 83.5-4 Near east coast of Honshu, Japan
    200814722008-05-07 17:28:56.036.33141.913318-5.2/ 124-4.5 Near east coast of Honshu, Japan
    200814732008-05-07 17:31:16.036.3141.63329-5.4/ 94.5 Near east coast of Honshu, Japan
    200814742008-05-07 17:40:55.036.32141.863321-4.9/ 133-3.5 Near east coast of Honshu, Japan
    200814762008-05-07 18:19:57.036.22141.463329-5.5/ 184.5-5 Near east coast of Honshu, Japan
    200814772008-05-07 18:39:36.036.32141.893323-4.7/ 122.5-3 Near east coast of Honshu, Japan
    200814782008-05-07 19:20:21.036.36141.473326-5.3/ 154-4.5 Near east coast of Honshu, Japan
    200814822008-05-08 05:26:30.036.18141.953322-5.1/ 133.5-4 Near east coast of Honshu, Japan
    200814832008-05-08 06:29:11.036.66141.783316-4.8/ 93-3.5 Near east coast of Honshu, Japan
    200814842008-05-08 09:40:37.036.4141.943325-5.1/ 153.5-4 Near east coast of Honshu, Japan
    200814852008-05-08 09:48:39.035.86142.43322-4.7/ 142.5-3 Off east coast of Honshu, Japan
    Macroseismic manifestations
         In accordance with ITAR TASS media agency "at least two people were injured after the series of the earthquakes at the east of Japan. This earthquake caused temporary switch off electricity in the number of Japanese towns of Ibaraki prefecture. Rather strong shocks were felt by the residents of all adjacent prefectures, including the capital".
    Focal mechanism and seismic moment of the earthquake
         Focal mechanism of the earthquake 08.05.2008 was obtained in NEIC with TMC method (table 2). This earthquake has occurred under prevailing action of compression forces oriented to the south-eastern direction. The motion along the flat nodal plane (NP2) with south-western direction of propagation was presented by the thrust (with components of right side drift), and along the steeply falling plane (NP1) by nearly meridian parallel orientation – characterized by uplift (with components of left side drift). The value of seismic moment Мо of the earthquake 08.05.2008 in accordance with NEIC made 1.8* 10** 19 n*m, the value of moment magnitude calculated from Kanamori formula is equal to Мw=6.8.
    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
    6026428105 81087481218 19119NEIC
  • NEIC - National Earthquakes Information Center of US Geological Service

    • Figure 4


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